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-<HEAD>
-<TITLE>A Hacker's Guide to Ncurses Internals</TITLE>
-<link rev="made" href="mailto:bugs-ncurses@gnu.org">
-<meta http-equiv="Content-Type" content="text/html; charset=iso-8859-1">
-<!--
-This document is self-contained, *except* that there is one relative link to
-the ncurses-intro.html document, expected to be in the same directory with
-this one.
--->
-</HEAD>
-<BODY>
-
-<H1>A Hacker's Guide to NCURSES</H1>
-
-<H1>Contents</H1>
-<UL>
-<LI><A HREF="#abstract">Abstract</A>
-<LI><A HREF="#objective">Objective of the Package</A>
-<UL>
-<LI><A HREF="#whysvr4">Why System V Curses?</A>
-<LI><A HREF="#extensions">How to Design Extensions</A>
-</UL>
-<LI><A HREF="#portability">Portability and Configuration</A>
-<LI><A HREF="#documentation">Documentation Conventions</A>
-<LI><A HREF="#bugtrack">How to Report Bugs</A>
-<LI><A HREF="#ncurslib">A Tour of the Ncurses Library</A>
-<UL>
-<LI><A HREF="#loverview">Library Overview</A>
-<LI><A HREF="#engine">The Engine Room</A>
-<LI><A HREF="#input">Keyboard Input</A>
-<LI><A HREF="#mouse">Mouse Events</A>
-<LI><A HREF="#output">Output and Screen Updating</A>
-</UL>
-<LI><A HREF="#fmnote">The Forms and Menu Libraries</A>
-<LI><A HREF="#tic">A Tour of the Terminfo Compiler</A>
-<UL>
-<LI><A HREF="#nonuse">Translation of Non-<STRONG>use</STRONG> Capabilities</A>
-<LI><A HREF="#uses">Use Capability Resolution</A>
-<LI><A HREF="#translation">Source-Form Translation</A>
-</UL>
-<LI><A HREF="#utils">Other Utilities</A>
-<LI><A HREF="#style">Style Tips for Developers</A>
-<LI><A HREF="#port">Porting Hints</A>
-</UL>
-
-<H1><A NAME="abstract">Abstract</A></H1>
-
-This document is a hacker's tour of the <STRONG>ncurses</STRONG> library and utilities.
-It discusses design philosophy, implementation methods, and the
-conventions used for coding and documentation. It is recommended
-reading for anyone who is interested in porting, extending or improving the
-package.
-
-<H1><A NAME="objective">Objective of the Package</A></H1>
-
-The objective of the <STRONG>ncurses</STRONG> package is to provide a free software API for
-character-cell terminals and terminal emulators with the following
-characteristics:
-
-<UL>
-<LI>Source-compatible with historical curses implementations (including
- the original BSD curses and System V curses.
-<LI>Conformant with the XSI Curses standard issued as part of XPG4 by
- X/Open.
-<LI>High-quality -- stable and reliable code, wide portability, good
- packaging, superior documentation.
-<LI>Featureful -- should eliminate as much of the drudgery of C interface
- programming as possible, freeing programmers to think at a higher
- level of design.
-</UL>
-
-These objectives are in priority order. So, for example, source
-compatibility with older version must trump featurefulness -- we cannot
-add features if it means breaking the portion of the API corresponding
-to historical curses versions.
-
-<H2><A NAME="whysvr4">Why System V Curses?</A></H2>
-
-We used System V curses as a model, reverse-engineering their API, in
-order to fulfill the first two objectives. <P>
-
-System V curses implementations can support BSD curses programs with
-just a recompilation, so by capturing the System V API we also
-capture BSD's. <P>
-
-More importantly for the future, the XSI Curses standard issued by X/Open
-is explicitly and closely modeled on System V. So conformance with
-System V took us most of the way to base-level XSI conformance.
-
-<H2><A NAME="extensions">How to Design Extensions</A></H2>
-
-The third objective (standards conformance) requires that it be easy to
-condition source code using <STRONG>ncurses</STRONG> so that the absence of nonstandard
-extensions does not break the code. <P>
-
-Accordingly, we have a policy of associating with each nonstandard extension
-a feature macro, so that ncurses client code can use this macro to condition
-in or out the code that requires the <STRONG>ncurses</STRONG> extension. <P>
-
-For example, there is a macro <CODE>NCURSES_MOUSE_VERSION</CODE> which XSI Curses
-does not define, but which is defined in the <STRONG>ncurses</STRONG> library header.
-You can use this to condition the calls to the mouse API calls.
-
-<H1><A NAME="portability">Portability and Configuration</A></H1>
-
-Code written for <STRONG>ncurses</STRONG> may assume an ANSI-standard C compiler and
-POSIX-compatible OS interface. It may also assume the presence of a
-System-V-compatible <EM>select(2)</EM> call. <P>
-
-We encourage (but do not require) developers to make the code friendly
-to less-capable UNIX environments wherever possible. <P>
-
-We encourage developers to support OS-specific optimizations and methods
-not available under POSIX/ANSI, provided only that:
-
-<UL>
-<LI>All such code is properly conditioned so the build process does not
- attempt to compile it under a plain ANSI/POSIX environment.
-<LI>Adding such implementation methods does not introduce incompatibilities
- in the <STRONG>ncurses</STRONG> API between platforms.
-</UL>
-
-We use GNU <CODE>autoconf(1)</CODE> as a tool to deal with portability issues.
-The right way to leverage an OS-specific feature is to modify the autoconf
-specification files (configure.in and aclocal.m4) to set up a new feature
-macro, which you then use to condition your code.
-
-<H1><A NAME="documentation">Documentation Conventions</A></H1>
-
-There are three kinds of documentation associated with this package. Each
-has a different preferred format:
-
-<UL>
-<LI>Package-internal files (README, INSTALL, TO-DO etc.)
-<LI>Manual pages.
-<LI>Everything else (i.e., narrative documentation).
-</UL>
-
-Our conventions are simple:
-<OL>
-<LI><STRONG>Maintain package-internal files in plain text.</STRONG>
- The expected viewer for them <EM>more(1)</EM> or an editor window; there's
- no point in elaborate mark-up.
-
-<LI><STRONG>Mark up manual pages in the man macros.</STRONG> These have to be viewable
- through traditional <EM>man(1)</EM> programs.
-
-<LI><STRONG>Write everything else in HTML.</STRONG>
-</OL>
-
-When in doubt, HTMLize a master and use <EM>lynx(1)</EM> to generate
-plain ASCII (as we do for the announcement document). <P>
-
-The reason for choosing HTML is that it's (a) well-adapted for on-line
-browsing through viewers that are everywhere; (b) more easily readable
-as plain text than most other mark-ups, if you don't have a viewer; and (c)
-carries enough information that you can generate a nice-looking printed
-version from it. Also, of course, it make exporting things like the
-announcement document to WWW pretty trivial.
-
-<H1><A NAME="bugtrack">How to Report Bugs</A></H1>
-
-The <A NAME="bugreport">reporting address for bugs</A> is
-<A HREF="mailto:bug-ncurses@gnu.org">bug-ncurses@gnu.org</A>.
-This is a majordomo list; to join, write
-to <CODE>bug-ncurses-request@gnu.org</CODE> with a message containing the line:
-<PRE>
- subscribe <name>@<host.domain>
-</PRE>
-
-The <CODE>ncurses</CODE> code is maintained by a small group of
-volunteers. While we try our best to fix bugs promptly, we simply
-don't have a lot of hours to spend on elementary hand-holding. We rely
-on intelligent cooperation from our users. If you think you have
-found a bug in <CODE>ncurses</CODE>, there are some steps you can take
-before contacting us that will help get the bug fixed quickly. <P>
-
-In order to use our bug-fixing time efficiently, we put people who
-show us they've taken these steps at the head of our queue. This
-means that if you don't, you'll probably end up at the tail end and
-have to wait a while.
-
-<OL>
-<LI>Develop a recipe to reproduce the bug.
-<p>
-Bugs we can reproduce are likely to be fixed very quickly, often
-within days. The most effective single thing you can do to get a
-quick fix is develop a way we can duplicate the bad behavior --
-ideally, by giving us source for a small, portable test program that
-breaks the library. (Even better is a keystroke recipe using one of
-the test programs provided with the distribution.)
-
-<LI>Try to reproduce the bug on a different terminal type. <P>
-
-In our experience, most of the behaviors people report as library bugs
-are actually due to subtle problems in terminal descriptions. This is
-especially likely to be true if you're using a traditional
-asynchronous terminal or PC-based terminal emulator, rather than xterm
-or a UNIX console entry. <P>
-
-It's therefore extremely helpful if you can tell us whether or not your
-problem reproduces on other terminal types. Usually you'll have both
-a console type and xterm available; please tell us whether or not your
-bug reproduces on both. <P>
-
-If you have xterm available, it is also good to collect xterm reports for
-different window sizes. This is especially true if you normally use an
-unusual xterm window size -- a surprising number of the bugs we've seen
-are either triggered or masked by these.
-
-<LI>Generate and examine a trace file for the broken behavior. <P>
-
-Recompile your program with the debugging versions of the libraries.
-Insert a <CODE>trace()</CODE> call with the argument set to <CODE>TRACE_UPDATE</CODE>.
-(See <A HREF="ncurses-intro.html#debugging">"Writing Programs with
-NCURSES"</A> for details on trace levels.)
-Reproduce your bug, then look at the trace file to see what the library
-was actually doing. <P>
-
-Another frequent cause of apparent bugs is application coding errors
-that cause the wrong things to be put on the virtual screen. Looking
-at the virtual-screen dumps in the trace file will tell you immediately if
-this is happening, and save you from the possible embarrassment of being
-told that the bug is in your code and is your problem rather than ours. <P>
-
-If the virtual-screen dumps look correct but the bug persists, it's
-possible to crank up the trace level to give more and more information
-about the library's update actions and the control sequences it issues
-to perform them. The test directory of the distribution contains a
-tool for digesting these logs to make them less tedious to wade
-through. <P>
-
-Often you'll find terminfo problems at this stage by noticing that the
-escape sequences put out for various capabilities are wrong. If not,
-you're likely to learn enough to be able to characterize any bug in
-the screen-update logic quite exactly.
-
-<LI>Report details and symptoms, not just interpretations. <P>
-
-If you do the preceding two steps, it is very likely that you'll discover
-the nature of the problem yourself and be able to send us a fix. This
-will create happy feelings all around and earn you good karma for the first
-time you run into a bug you really can't characterize and fix yourself. <P>
-
-If you're still stuck, at least you'll know what to tell us. Remember, we
-need details. If you guess about what is safe to leave out, you are too
-likely to be wrong. <P>
-
-If your bug produces a bad update, include a trace file. Try to make
-the trace at the <EM>least</EM> voluminous level that pins down the
-bug. Logs that have been through tracemunch are OK, it doesn't throw
-away any information (actually they're better than un-munched ones because
-they're easier to read). <P>
-
-If your bug produces a core-dump, please include a symbolic stack trace
-generated by gdb(1) or your local equivalent. <P>
-
-Tell us about every terminal on which you've reproduced the bug -- and
-every terminal on which you can't. Ideally, sent us terminfo sources
-for all of these (yours might differ from ours). <P>
-
-Include your ncurses version and your OS/machine type, of course! You can
-find your ncurses version in the <CODE>curses.h</CODE> file.
-</OL>
-
-If your problem smells like a logic error or in cursor movement or
-scrolling or a bad capability, there are a couple of tiny test frames
-for the library algorithms in the progs directory that may help you
-isolate it. These are not part of the normal build, but do have their
-own make productions. <P>
-
-The most important of these is <CODE>mvcur</CODE>, a test frame for the
-cursor-movement optimization code. With this program, you can see
-directly what control sequences will be emitted for any given cursor
-movement or scroll/insert/delete operations. If you think you've got
-a bad capability identified, you can disable it and test again. The
-program is command-driven and has on-line help. <P>
-
-If you think the vertical-scroll optimization is broken, or just want to
-understand how it works better, build <CODE>hashmap</CODE> and read the
-header comments of <CODE>hardscroll.c</CODE> and <CODE>hashmap.c</CODE>; then try
-it out. You can also test the hardware-scrolling optimization separately
-with <CODE>hardscroll</CODE>. <P>
-
-<H1><A NAME="ncurslib">A Tour of the Ncurses Library</A></H1>
-
-<H2><A NAME="loverview">Library Overview</A></H2>
-
-Most of the library is superstructure -- fairly trivial convenience
-interfaces to a small set of basic functions and data structures used
-to manipulate the virtual screen (in particular, none of this code
-does any I/O except through calls to more fundamental modules
-described below). The files
-<blockquote>
-<CODE>
-lib_addch.c
-lib_bkgd.c
-lib_box.c
-lib_chgat.c
-lib_clear.c
-lib_clearok.c
-lib_clrbot.c
-lib_clreol.c
-lib_colorset.c
-lib_data.c
-lib_delch.c
-lib_delwin.c
-lib_echo.c
-lib_erase.c
-lib_gen.c
-lib_getstr.c
-lib_hline.c
-lib_immedok.c
-lib_inchstr.c
-lib_insch.c
-lib_insdel.c
-lib_insstr.c
-lib_instr.c
-lib_isendwin.c
-lib_keyname.c
-lib_leaveok.c
-lib_move.c
-lib_mvwin.c
-lib_overlay.c
-lib_pad.c
-lib_printw.c
-lib_redrawln.c
-lib_scanw.c
-lib_screen.c
-lib_scroll.c
-lib_scrollok.c
-lib_scrreg.c
-lib_set_term.c
-lib_slk.c
-lib_slkatr_set.c
-lib_slkatrof.c
-lib_slkatron.c
-lib_slkatrset.c
-lib_slkattr.c
-lib_slkclear.c
-lib_slkcolor.c
-lib_slkinit.c
-lib_slklab.c
-lib_slkrefr.c
-lib_slkset.c
-lib_slktouch.c
-lib_touch.c
-lib_unctrl.c
-lib_vline.c
-lib_wattroff.c
-lib_wattron.c
-lib_window.c
-</CODE>
-</blockquote>
-are all in this category. They are very
-unlikely to need change, barring bugs or some fundamental
-reorganization in the underlying data structures. <P>
-
-These files are used only for debugging support:
-<blockquote>
-<code>
-lib_trace.c
-lib_traceatr.c
-lib_tracebits.c
-lib_tracechr.c
-lib_tracedmp.c
-lib_tracemse.c
-trace_buf.c
-</code>
-</blockquote>
-It is rather unlikely you will ever need to change these, unless
-you want to introduce a new debug trace level for some reason.<P>
-
-There is another group of files that do direct I/O via <EM>tputs()</EM>,
-computations on the terminal capabilities, or queries to the OS
-environment, but nevertheless have only fairly low complexity. These
-include:
-<blockquote>
-<code>
-lib_acs.c
-lib_beep.c
-lib_color.c
-lib_endwin.c
-lib_initscr.c
-lib_longname.c
-lib_newterm.c
-lib_options.c
-lib_termcap.c
-lib_ti.c
-lib_tparm.c
-lib_tputs.c
-lib_vidattr.c
-read_entry.c.
-</code>
-</blockquote>
-They are likely to need revision only if
-ncurses is being ported to an environment without an underlying
-terminfo capability representation. <P>
-
-These files
-have serious hooks into
-the tty driver and signal facilities:
-<blockquote>
-<code>
-lib_kernel.c
-lib_baudrate.c
-lib_raw.c
-lib_tstp.c
-lib_twait.c
-</code>
-</blockquote>
-If you run into porting snafus
-moving the package to another UNIX, the problem is likely to be in one
-of these files.
-The file <CODE>lib_print.c</CODE> uses sleep(2) and also
-falls in this category.<P>
-
-Almost all of the real work is done in the files
-<blockquote>
-<code>
-hardscroll.c
-hashmap.c
-lib_addch.c
-lib_doupdate.c
-lib_getch.c
-lib_mouse.c
-lib_mvcur.c
-lib_refresh.c
-lib_setup.c
-lib_vidattr.c
-</code>
-</blockquote>
-Most of the algorithmic complexity in the
-library lives in these files.
-If there is a real bug in <STRONG>ncurses</STRONG> itself, it's probably here.
-We'll tour some of these files in detail
-below (see <A HREF="#engine">The Engine Room</A>). <P>
-
-Finally, there is a group of files that is actually most of the
-terminfo compiler. The reason this code lives in the <STRONG>ncurses</STRONG>
-library is to support fallback to /etc/termcap. These files include
-<blockquote>
-<code>
-alloc_entry.c
-captoinfo.c
-comp_captab.c
-comp_error.c
-comp_hash.c
-comp_parse.c
-comp_scan.c
-parse_entry.c
-read_termcap.c
-write_entry.c
-</code>
-</blockquote>
-We'll discuss these in the compiler tour.
-
-<H2><A NAME="engine">The Engine Room</A></H2>
-
-<H3><A NAME="input">Keyboard Input</A></H3>
-
-All <CODE>ncurses</CODE> input funnels through the function
-<CODE>wgetch()</CODE>, defined in <CODE>lib_getch.c</CODE>. This function is
-tricky; it has to poll for keyboard and mouse events and do a running
-match of incoming input against the set of defined special keys. <P>
-
-The central data structure in this module is a FIFO queue, used to
-match multiple-character input sequences against special-key
-capabilities; also to implement pushback via <CODE>ungetch()</CODE>. <P>
-
-The <CODE>wgetch()</CODE> code distinguishes between function key
-sequences and the same sequences typed manually by doing a timed wait
-after each input character that could lead a function key sequence.
-If the entire sequence takes less than 1 second, it is assumed to have
-been generated by a function key press. <P>
-
-Hackers bruised by previous encounters with variant <CODE>select(2)</CODE>
-calls may find the code in <CODE>lib_twait.c</CODE> interesting. It deals
-with the problem that some BSD selects don't return a reliable
-time-left value. The function <CODE>timed_wait()</CODE> effectively
-simulates a System V select.
-
-<H3><A NAME="mouse">Mouse Events</A></H3>
-
-If the mouse interface is active, <CODE>wgetch()</CODE> polls for mouse
-events each call, before it goes to the keyboard for input. It is
-up to <CODE>lib_mouse.c</CODE> how the polling is accomplished; it may vary
-for different devices. <P>
-
-Under xterm, however, mouse event notifications come in via the keyboard
-input stream. They are recognized by having the <STRONG>kmous</STRONG> capability
-as a prefix. This is kind of klugey, but trying to wire in recognition of
-a mouse key prefix without going through the function-key machinery would
-be just too painful, and this turns out to imply having the prefix somewhere
-in the function-key capabilities at terminal-type initialization. <P>
-
-This kluge only works because <STRONG>kmous</STRONG> isn't actually used by any
-historic terminal type or curses implementation we know of. Best
-guess is it's a relic of some forgotten experiment in-house at Bell
-Labs that didn't leave any traces in the publicly-distributed System V
-terminfo files. If System V or XPG4 ever gets serious about using it
-again, this kluge may have to change. <P>
-
-Here are some more details about mouse event handling: <P>
-
-The <CODE>lib_mouse()</CODE>code is logically split into a lower level that
-accepts event reports in a device-dependent format and an upper level that
-parses mouse gestures and filters events. The mediating data structure is a
-circular queue of event structures. <P>
-
-Functionally, the lower level's job is to pick up primitive events and
-put them on the circular queue. This can happen in one of two ways:
-either (a) <CODE>_nc_mouse_event()</CODE> detects a series of incoming
-mouse reports and queues them, or (b) code in <CODE>lib_getch.c</CODE> detects the
-<STRONG>kmous</STRONG> prefix in the keyboard input stream and calls _nc_mouse_inline
-to queue up a series of adjacent mouse reports. <P>
-
-In either case, <CODE>_nc_mouse_parse()</CODE> should be called after the
-series is accepted to parse the digested mouse reports (low-level
-events) into a gesture (a high-level or composite event).
-
-<H3><A NAME="output">Output and Screen Updating</A></H3>
-
-With the single exception of character echoes during a <CODE>wgetnstr()</CODE>
-call (which simulates cooked-mode line editing in an ncurses window),
-the library normally does all its output at refresh time. <P>
-
-The main job is to go from the current state of the screen (as represented
-in the <CODE>curscr</CODE> window structure) to the desired new state (as
-represented in the <CODE>newscr</CODE> window structure), while doing as
-little I/O as possible. <P>
-
-The brains of this operation are the modules <CODE>hashmap.c</CODE>,
-<CODE>hardscroll.c</CODE> and <CODE>lib_doupdate.c</CODE>; the latter two use
-<CODE>lib_mvcur.c</CODE>. Essentially, what happens looks like this: <P>
-
-The <CODE>hashmap.c</CODE> module tries to detect vertical motion
-changes between the real and virtual screens. This information
-is represented by the oldindex members in the newscr structure.
-These are modified by vertical-motion and clear operations, and both are
-re-initialized after each update. To this change-journalling
-information, the hashmap code adds deductions made using a modified Heckel
-algorithm on hash values generated from the line contents. <P>
-
-The <CODE>hardscroll.c</CODE> module computes an optimum set of scroll,
-insertion, and deletion operations to make the indices match. It calls
-<CODE>_nc_mvcur_scrolln()</CODE> in <CODE>lib_mvcur.c</CODE> to do those motions. <P>
-
-Then <CODE>lib_doupdate.c</CODE> goes to work. Its job is to do line-by-line
-transformations of <CODE>curscr</CODE> lines to <CODE>newscr</CODE> lines. Its main
-tool is the routine <CODE>mvcur()</CODE> in <CODE>lib_mvcur.c</CODE>. This routine
-does cursor-movement optimization, attempting to get from given screen
-location A to given location B in the fewest output characters possible. <P>
-
-If you want to work on screen optimizations, you should use the fact
-that (in the trace-enabled version of the library) enabling the
-<CODE>TRACE_TIMES</CODE> trace level causes a report to be emitted after
-each screen update giving the elapsed time and a count of characters
-emitted during the update. You can use this to tell when an update
-optimization improves efficiency. <P>
-
-In the trace-enabled version of the library, it is also possible to disable
-and re-enable various optimizations at runtime by tweaking the variable
-<CODE>_nc_optimize_enable</CODE>. See the file <CODE>include/curses.h.in</CODE>
-for mask values, near the end.
-
-<H1><A NAME="fmnote">The Forms and Menu Libraries</A></H1>
-
-The forms and menu libraries should work reliably in any environment you
-can port ncurses to. The only portability issue anywhere in them is what
-flavor of regular expressions the built-in form field type TYPE_REGEXP
-will recognize. <P>
-
-The configuration code prefers the POSIX regex facility, modeled on
-System V's, but will settle for BSD regexps if the former isn't available. <P>
-
-Historical note: the panels code was written primarily to assist in
-porting u386mon 2.0 (comp.sources.misc v14i001-4) to systems lacking
-panels support; u386mon 2.10 and beyond use it. This version has been
-slightly cleaned up for <CODE>ncurses</CODE>.
-
-<H1><A NAME="tic">A Tour of the Terminfo Compiler</A></H1>
-
-The <STRONG>ncurses</STRONG> implementation of <STRONG>tic</STRONG> is rather complex
-internally; it has to do a trying combination of missions. This starts
-with the fact that, in addition to its normal duty of compiling
-terminfo sources into loadable terminfo binaries, it has to be able to
-handle termcap syntax and compile that too into terminfo entries. <P>
-
-The implementation therefore starts with a table-driven, dual-mode
-lexical analyzer (in <CODE>comp_scan.c</CODE>). The lexer chooses its
-mode (termcap or terminfo) based on the first `,' or `:' it finds in
-each entry. The lexer does all the work of recognizing capability
-names and values; the grammar above it is trivial, just "parse entries
-till you run out of file".
-
-<H2><A NAME="nonuse">Translation of Non-<STRONG>use</STRONG> Capabilities</A></H2>
-
-Translation of most things besides <STRONG>use</STRONG> capabilities is pretty
-straightforward. The lexical analyzer's tokenizer hands each capability
-name to a hash function, which drives a table lookup. The table entry
-yields an index which is used to look up the token type in another table,
-and controls interpretation of the value. <P>
-
-One possibly interesting aspect of the implementation is the way the
-compiler tables are initialized. All the tables are generated by various
-awk/sed/sh scripts from a master table <CODE>include/Caps</CODE>; these
-scripts actually write C initializers which are linked to the compiler.
-Furthermore, the hash table is generated in the same way, so it doesn't
-have to be generated at compiler startup time (another benefit of this
-organization is that the hash table can be in shareable text space). <P>
-
-Thus, adding a new capability is usually pretty trivial, just a matter
-of adding one line to the <CODE>include/Caps</CODE> file. We'll have more
-to say about this in the section on <A HREF="#translation">Source-Form
-Translation</A>.
-
-<H2><A NAME="uses">Use Capability Resolution</A></H2>
-
-The background problem that makes <STRONG>tic</STRONG> tricky isn't the capability
-translation itself, it's the resolution of <STRONG>use</STRONG> capabilities. Older
-versions would not handle forward <STRONG>use</STRONG> references for this reason
-(that is, a using terminal always had to follow its use target in the
-source file). By doing this, they got away with a simple implementation
-tactic; compile everything as it blows by, then resolve uses from compiled
-entries. <P>
-
-This won't do for <STRONG>ncurses</STRONG>. The problem is that that the whole
-compilation process has to be embeddable in the <STRONG>ncurses</STRONG> library
-so that it can be called by the startup code to translate termcap
-entries on the fly. The embedded version can't go promiscuously writing
-everything it translates out to disk -- for one thing, it will typically
-be running with non-root permissions. <P>
-
-So our <STRONG>tic</STRONG> is designed to parse an entire terminfo file into a
-doubly-linked circular list of entry structures in-core, and then do
-<STRONG>use</STRONG> resolution in-memory before writing everything out. This
-design has other advantages: it makes forward and back use-references
-equally easy (so we get the latter for free), and it makes checking for
-name collisions before they're written out easy to do. <P>
-
-And this is exactly how the embedded version works. But the stand-alone
-user-accessible version of <STRONG>tic</STRONG> partly reverts to the historical
-strategy; it writes to disk (not keeping in core) any entry with no
-<STRONG>use</STRONG> references. <P>
-
-This is strictly a core-economy kluge, implemented because the
-terminfo master file is large enough that some core-poor systems swap
-like crazy when you compile it all in memory...there have been reports of
-this process taking <STRONG>three hours</STRONG>, rather than the twenty seconds
-or less typical on the author's development box. <P>
-
-So. The executable <STRONG>tic</STRONG> passes the entry-parser a hook that
-<EM>immediately</EM> writes out the referenced entry if it has no use
-capabilities. The compiler main loop refrains from adding the entry
-to the in-core list when this hook fires. If some other entry later
-needs to reference an entry that got written immediately, that's OK;
-the resolution code will fetch it off disk when it can't find it in
-core. <P>
-
-Name collisions will still be detected, just not as cleanly. The
-<CODE>write_entry()</CODE> code complains before overwriting an entry that
-postdates the time of <STRONG>tic</STRONG>'s first call to
-<CODE>write_entry()</CODE>, Thus it will complain about overwriting
-entries newly made during the <STRONG>tic</STRONG> run, but not about
-overwriting ones that predate it.
-
-<H2><A NAME="translation">Source-Form Translation</A></H2>
-
-Another use of <STRONG>tic</STRONG> is to do source translation between various termcap
-and terminfo formats. There are more variants out there than you might
-think; the ones we know about are described in the <STRONG>captoinfo(1)</STRONG>
-manual page. <P>
-
-The translation output code (<CODE>dump_entry()</CODE> in
-<CODE>ncurses/dump_entry.c</CODE>) is shared with the <STRONG>infocmp(1)</STRONG>
-utility. It takes the same internal representation used to generate
-the binary form and dumps it to standard output in a specified
-format. <P>
-
-The <CODE>include/Caps</CODE> file has a header comment describing ways you
-can specify source translations for nonstandard capabilities just by
-altering the master table. It's possible to set up capability aliasing
-or tell the compiler to plain ignore a given capability without writing
-any C code at all. <P>
-
-For circumstances where you need to do algorithmic translation, there
-are functions in <CODE>parse_entry.c</CODE> called after the parse of each
-entry that are specifically intended to encapsulate such
-translations. This, for example, is where the AIX <STRONG>box1</STRONG> capability
-get translated to an <STRONG>acsc</STRONG> string.
-
-<H1><A NAME="utils">Other Utilities</A></H1>
-
-The <STRONG>infocmp</STRONG> utility is just a wrapper around the same
-entry-dumping code used by <STRONG>tic</STRONG> for source translation. Perhaps
-the one interesting aspect of the code is the use of a predicate
-function passed in to <CODE>dump_entry()</CODE> to control which
-capabilities are dumped. This is necessary in order to handle both
-the ordinary De-compilation case and entry difference reporting. <P>
-
-The <STRONG>tput</STRONG> and <STRONG>clear</STRONG> utilities just do an entry load
-followed by a <CODE>tputs()</CODE> of a selected capability.
-
-<H1><A NAME="style">Style Tips for Developers</A></H1>
-
-See the TO-DO file in the top-level directory of the source distribution
-for additions that would be particularly useful. <P>
-
-The prefix <CODE>_nc_</CODE> should be used on library public functions that are
-not part of the curses API in order to prevent pollution of the
-application namespace.
-
-If you have to add to or modify the function prototypes in curses.h.in,
-read ncurses/MKlib_gen.sh first so you can avoid breaking XSI conformance.
-
-Please join the ncurses mailing list. See the INSTALL file in the
-top level of the distribution for details on the list. <P>
-
-Look for the string <CODE>FIXME</CODE> in source files to tag minor bugs
-and potential problems that could use fixing. <P>
-
-Don't try to auto-detect OS features in the main body of the C code.
-That's the job of the configuration system. <P>
-
-To hold down complexity, do make your code data-driven. Especially,
-if you can drive logic from a table filtered out of
-<CODE>include/Caps</CODE>, do it. If you find you need to augment the
-data in that file in order to generate the proper table, that's still
-preferable to ad-hoc code -- that's why the fifth field (flags) is
-there. <P>
-
-Have fun!
-
-<H1><A NAME="port">Porting Hints</A></H1>
-
-The following notes are intended to be a first step towards DOS and Macintosh
-ports of the ncurses libraries. <P>
-
-The following library modules are `pure curses'; they operate only on
-the curses internal structures, do all output through other curses
-calls (not including <CODE>tputs()</CODE> and <CODE>putp()</CODE>) and do not
-call any other UNIX routines such as signal(2) or the stdio library.
-Thus, they should not need to be modified for single-terminal
-ports.
-
-<blockquote>
-<code>
-lib_addch.c
-lib_addstr.c
-lib_bkgd.c
-lib_box.c
-lib_clear.c
-lib_clrbot.c
-lib_clreol.c
-lib_delch.c
-lib_delwin.c
-lib_erase.c
-lib_inchstr.c
-lib_insch.c
-lib_insdel.c
-lib_insstr.c
-lib_keyname.c
-lib_move.c
-lib_mvwin.c
-lib_newwin.c
-lib_overlay.c
-lib_pad.c
-lib_printw.c
-lib_refresh.c
-lib_scanw.c
-lib_scroll.c
-lib_scrreg.c
-lib_set_term.c
-lib_touch.c
-lib_tparm.c
-lib_tputs.c
-lib_unctrl.c
-lib_window.c
-panel.c
-</code>
-</blockquote>
-<P>
-
-This module is pure curses, but calls outstr():
-
-<blockquote>
-<code>
-lib_getstr.c
-</code>
-</blockquote>
-<P>
-
-These modules are pure curses, except that they use <CODE>tputs()</CODE>
-and <CODE>putp()</CODE>:
-
-<blockquote>
-<code>
-lib_beep.c
-lib_color.c
-lib_endwin.c
-lib_options.c
-lib_slk.c
-lib_vidattr.c
-</code>
-</blockquote>
-<P>
-
-This modules assist in POSIX emulation on non-POSIX systems:
-<DL>
-<DT> sigaction.c
-<DD> signal calls
-</DL>
-
-The following source files will not be needed for a
-single-terminal-type port.
-
-<blockquote>
-<code>
-alloc_entry.c
-captoinfo.c
-clear.c
-comp_captab.c
-comp_error.c
-comp_hash.c
-comp_main.c
-comp_parse.c
-comp_scan.c
-dump_entry.c
-infocmp.c
-parse_entry.c
-read_entry.c
-tput.c
-write_entry.c
-</code>
-</blockquote>
-<P>
-
-The following modules will use open()/read()/write()/close()/lseek() on files,
-but no other OS calls.
-
-<DL>
-<DT>lib_screen.c
-<DD>used to read/write screen dumps
-<DT>lib_trace.c
-<DD>used to write trace data to the logfile
-</DL>
-
-Modules that would have to be modified for a port start here: <P>
-
-The following modules are `pure curses' but contain assumptions inappropriate
-for a memory-mapped port.
-
-<dl>
-<dt>lib_longname.c<dd>assumes there may be multiple terminals
-<dt>lib_acs.c<dd>assumes acs_map as a double indirection
-<dt>lib_mvcur.c<dd>assumes cursor moves have variable cost
-<dt>lib_termcap.c<dd>assumes there may be multiple terminals
-<dt>lib_ti.c<dd>assumes there may be multiple terminals
-</dl>
-
-The following modules use UNIX-specific calls:
-
-<dl>
-<dt>lib_doupdate.c<dd>input checking
-<dt>lib_getch.c<dd>read()
-<dt>lib_initscr.c<dd>getenv()
-<dt>lib_newterm.c
-<dt>lib_baudrate.c
-<dt>lib_kernel.c<dd>various tty-manipulation and system calls
-<dt>lib_raw.c<dd>various tty-manipulation calls
-<dt>lib_setup.c<dd>various tty-manipulation calls
-<dt>lib_restart.c<dd>various tty-manipulation calls
-<dt>lib_tstp.c<dd>signal-manipulation calls
-<dt>lib_twait.c<dd>gettimeofday(), select().
-</dl>
-
-<HR>
-<ADDRESS>Eric S. Raymond <esr@snark.thyrsus.com></ADDRESS>
-(Note: This is <EM>not</EM> the <A HREF="#bugtrack">bug address</A>!)
-</BODY>
-</HTML>
+++ /dev/null
-<!DOCTYPE HTML PUBLIC "-//IETF//DTD HTML 3.0//EN">
-<!--
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- * distribute, distribute with modifications, sublicense, and/or sell *
- * copies of the Software, and to permit persons to whom the Software is *
- * furnished to do so, subject to the following conditions: *
- * *
- * The above copyright notice and this permission notice shall be included *
- * in all copies or substantial portions of the Software. *
- * *
- * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS *
- * OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF *
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- * IN NO EVENT SHALL THE ABOVE COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, *
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- * Except as contained in this notice, the name(s) of the above copyright *
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- ****************************************************************************
--->
-<HTML>
-<HEAD>
-<TITLE>Writing Programs with NCURSES</TITLE>
-<link rev="made" href="mailto:bugs-ncurses@gnu.org">
-<meta http-equiv="Content-Type" content="text/html; charset=iso-8859-1">
-</HEAD>
-<BODY>
-
-<H1>Writing Programs with NCURSES</H1>
-
-<BLOCKQUOTE>
-by Eric S. Raymond and Zeyd M. Ben-Halim<BR>
-updates since release 1.9.9e by Thomas Dickey
-</BLOCKQUOTE>
-
-<H1>Contents</H1>
-<UL>
-<LI><A HREF="#introduction">Introduction</A>
-<UL>
-<LI><A HREF="#history">A Brief History of Curses</A>
-<LI><A HREF="#scope">Scope of This Document</A>
-<LI><A HREF="#terminology">Terminology</A>
-</UL>
-<LI><A HREF="#curses">The Curses Library</A>
-<UL>
-<LI><A HREF="#overview">An Overview of Curses</A>
-<UL>
-<LI><A HREF="#compiling">Compiling Programs using Curses</A>
-<LI><A HREF="#updating">Updating the Screen</A>
-<LI><A HREF="#stdscr">Standard Windows and Function Naming Conventions</A>
-<LI><A HREF="#variables">Variables</A>
-</UL>
-<LI><A HREF="#using">Using the Library</A>
-<UL>
-<LI><A HREF="#starting">Starting up</A>
-<LI><A HREF="#output">Output</A>
-<LI><A HREF="#input">Input</A>
-<LI><A HREF="#formschars">Using Forms Characters</A>
-<LI><A HREF="#attributes">Character Attributes and Color</A>
-<LI><A HREF="#mouse">Mouse Interfacing</A>
-<LI><A HREF="#finishing">Finishing Up</A>
-</UL>
-<LI><A HREF="#functions">Function Descriptions</A>
-<UL>
-<LI><A HREF="#init">Initialization and Wrapup</A>
-<LI><A HREF="#flush">Causing Output to the Terminal</A>
-<LI><A HREF="#lowlevel">Low-Level Capability Access</A>
-<LI><A HREF="#debugging">Debugging</A>
-</UL>
-<LI><A HREF="#hints">Hints, Tips, and Tricks</A>
-<UL>
-<LI><A HREF="#caution">Some Notes of Caution</A>
-<LI><A HREF="#leaving">Temporarily Leaving ncurses Mode</A>
-<LI><A HREF="#xterm">Using <CODE>ncurses</CODE> under <CODE>xterm</CODE></A>
-<LI><A HREF="#screens">Handling Multiple Terminal Screens</A>
-<LI><A HREF="#testing">Testing for Terminal Capabilities</A>
-<LI><A HREF="#tuning">Tuning for Speed</A>
-<LI><A HREF="#special">Special Features of <CODE>ncurses</CODE></A>
-</UL>
-<LI><A HREF="#compat">Compatibility with Older Versions</A>
-<UL>
-<LI><A HREF="#refbug">Refresh of Overlapping Windows</A>
-<LI><A HREF="#backbug">Background Erase</A>
-</UL>
-<LI><A HREF="#xsifuncs">XSI Curses Conformance</A>
-</UL>
-<LI><A HREF="#panels">The Panels Library</A>
-<UL>
-<LI><A HREF="#pcompile">Compiling With the Panels Library</A>
-<LI><A HREF="#poverview">Overview of Panels</A>
-<LI><A HREF="#pstdscr">Panels, Input, and the Standard Screen</A>
-<LI><A HREF="#hiding">Hiding Panels</A>
-<LI><A HREF="#pmisc">Miscellaneous Other Facilities</A>
-</UL>
-<LI><A HREF="#menu">The Menu Library</A>
-<UL>
-<LI><A HREF="#mcompile">Compiling with the menu Library</A>
-<LI><A HREF="#moverview">Overview of Menus</A>
-<LI><A HREF="#mselect">Selecting items</A>
-<LI><A HREF="#mdisplay">Menu Display</A>
-<LI><A HREF="#mwindows">Menu Windows</A>
-<LI><A HREF="#minput">Processing Menu Input</A>
-<LI><A HREF="#mmisc">Miscellaneous Other Features</A>
-</UL>
-<LI><A HREF="#form">The Forms Library</A>
-<UL>
-<LI><A HREF="#fcompile">Compiling with the forms Library</A>
-<LI><A HREF="#foverview">Overview of Forms</A>
-<LI><A HREF="#fcreate">Creating and Freeing Fields and Forms</A>
-<LI><A HREF="#fattributes">Fetching and Changing Field Attributes</A>
-<UL>
-<LI><A HREF="#fsizes">Fetching Size and Location Data</A>
-<LI><A HREF="#flocation">Changing the Field Location</A>
-<LI><A HREF="#fjust">The Justification Attribute</A>
-<LI><A HREF="#fdispatts">Field Display Attributes</A>
-<LI><A HREF="#foptions">Field Option Bits</A>
-<LI><A HREF="#fstatus">Field Status</A>
-<LI><A HREF="#fuser">Field User Pointer</A>
-</UL>
-<LI><A HREF="#fdynamic">Variable-Sized Fields</A>
-<LI><A HREF="#fvalidation">Field Validation</A>
-<UL>
-<LI><A HREF="#ftype_alpha">TYPE_ALPHA</A>
-<LI><A HREF="#ftype_alnum">TYPE_ALNUM</A>
-<LI><A HREF="#ftype_enum">TYPE_ENUM</A>
-<LI><A HREF="#ftype_integer">TYPE_INTEGER</A>
-<LI><A HREF="#ftype_numeric">TYPE_NUMERIC</A>
-<LI><A HREF="#ftype_regexp">TYPE_REGEXP</A>
-</UL>
-<LI><A HREF="#fbuffer">Direct Field Buffer Manipulation</A>
-<LI><A HREF="#formattrs">Attributes of Forms</A>
-<LI><A HREF="#fdisplay">Control of Form Display</A>
-<LI><A HREF="#fdriver">Input Processing in the Forms Driver</A>
-<UL>
-<LI><A HREF="#fpage">Page Navigation Requests</A>
-<LI><A HREF="#ffield">Inter-Field Navigation Requests</A>
-<LI><A HREF="#fifield">Intra-Field Navigation Requests</A>
-<LI><A HREF="#fscroll">Scrolling Requests</A>
-<LI><A HREF="#fedit">Field Editing Requests</A>
-<LI><A HREF="#forder">Order Requests</A>
-<LI><A HREF="#fappcmds">Application Commands</A>
-</UL>
-<LI><A HREF="#fhooks">Field Change Hooks</A>
-<LI><A HREF="#ffocus">Field Change Commands</A>
-<LI><A HREF="#frmoptions">Form Options</A>
-<LI><A HREF="#fcustom">Custom Validation Types</A>
-<UL>
-<LI><A HREF="#flinktypes">Union Types</A>
-<LI><A HREF="#fnewtypes">New Field Types</A>
-<LI><A HREF="#fcheckargs">Validation Function Arguments</A>
-<LI><A HREF="#fcustorder">Order Functions For Custom Types</A>
-<LI><A HREF="#fcustprobs">Avoiding Problems</A>
-</UL>
-</UL>
-</UL>
-
-<HR>
-<H1><A NAME="introduction">Introduction</A></H1>
-
-This document is an introduction to programming with <CODE>curses</CODE>. It is
-not an exhaustive reference for the curses Application Programming Interface
-(API); that role is filled by the <CODE>curses</CODE> manual pages. Rather, it
-is intended to help C programmers ease into using the package. <P>
-
-This document is aimed at C applications programmers not yet specifically
-familiar with ncurses. If you are already an experienced <CODE>curses</CODE>
-programmer, you should nevertheless read the sections on
-<A HREF="#mouse">Mouse Interfacing</A>, <A HREF="#debugging">Debugging</A>,
-<A HREF="#compat">Compatibility with Older Versions</A>,
-and <A HREF="#hints">Hints, Tips, and Tricks</A>. These will bring you up
-to speed on the special features and quirks of the <CODE>ncurses</CODE>
-implementation. If you are not so experienced, keep reading. <P>
-
-The <CODE>curses</CODE> package is a subroutine library for
-terminal-independent screen-painting and input-event handling which
-presents a high level screen model to the programmer, hiding differences
-between terminal types and doing automatic optimization of output to change
-one screen full of text into another. <CODE>Curses</CODE> uses terminfo, which
-is a database format that can describe the capabilities of thousands of
-different terminals. <P>
-
-The <CODE>curses</CODE> API may seem something of an archaism on UNIX desktops
-increasingly dominated by X, Motif, and Tcl/Tk. Nevertheless, UNIX still
-supports tty lines and X supports <EM>xterm(1)</EM>; the <CODE>curses</CODE>
-API has the advantage of (a) back-portability to character-cell terminals,
-and (b) simplicity. For an application that does not require bit-mapped
-graphics and multiple fonts, an interface implementation using <CODE>curses</CODE>
-will typically be a great deal simpler and less expensive than one using an
-X toolkit.
-
-<H2><A NAME="history">A Brief History of Curses</A></H2>
-
-Historically, the first ancestor of <CODE>curses</CODE> was the routines written to
-provide screen-handling for the game <CODE>rogue</CODE>; these used the
-already-existing <CODE>termcap</CODE> database facility for describing terminal
-capabilities. These routines were abstracted into a documented library and
-first released with the early BSD UNIX versions. <P>
-
-System III UNIX from Bell Labs featured a rewritten and much-improved
-<CODE>curses</CODE> library. It introduced the terminfo format. Terminfo is based
-on Berkeley's termcap database, but contains a number of improvements and
-extensions. Parameterized capabilities strings were introduced, making it
-possible to describe multiple video attributes, and colors and to handle far
-more unusual terminals than possible with termcap. In the later AT&T
-System V releases, <CODE>curses</CODE> evolved to use more facilities and offer
-more capabilities, going far beyond BSD curses in power and flexibility.
-
-<H2><A NAME="scope">Scope of This Document</A></H2>
-
-This document describes <CODE>ncurses</CODE>, a free implementation of
-the System V <CODE>curses</CODE> API with some clearly marked extensions.
-It includes the following System V curses features:
-<UL>
-<LI>Support for multiple screen highlights (BSD curses could only
-handle one `standout' highlight, usually reverse-video).
-<LI>Support for line- and box-drawing using forms characters.
-<LI>Recognition of function keys on input.
-<LI>Color support.
-<LI>Support for pads (windows of larger than screen size on which the
-screen or a subwindow defines a viewport).
-</UL>
-
-Also, this package makes use of the insert and delete line and character
-features of terminals so equipped, and determines how to optimally use these
-features with no help from the programmer. It allows arbitrary combinations of
-video attributes to be displayed, even on terminals that leave ``magic
-cookies'' on the screen to mark changes in attributes. <P>
-
-The <CODE>ncurses</CODE> package can also capture and use event reports from a
-mouse in some environments (notably, xterm under the X window system). This
-document includes tips for using the mouse. <P>
-
-The <CODE>ncurses</CODE> package was originated by Pavel Curtis. The original
-maintainer of this package is
-<A HREF="mailto:zmbenhal@netcom.com">Zeyd Ben-Halim</A>
-<zmbenhal@netcom.com>.
-<A HREF="mailto:esr@snark.thyrsus.com">Eric S. Raymond</A>
-<esr@snark.thyrsus.com>
-wrote many of the new features in versions after 1.8.1
-and wrote most of this introduction.
-Jürgen Pfeifer
-wrote all of the menu and forms code as well as the
-<A HREF="http://www.adahome.com">Ada95</A> binding.
-Ongoing work is being done by
-<A HREF="mailto:dickey@invisible-island.net">Thomas Dickey</A> (maintainer).
-Contact the current maintainers at
-<A HREF="mailto:bug-ncurses@gnu.org">bug-ncurses@gnu.org</A>.
-<P>
-
-This document also describes the <A HREF="#panels">panels</A> extension library,
-similarly modeled on the SVr4 panels facility. This library allows you to
-associate backing store with each of a stack or deck of overlapping windows,
-and provides operations for moving windows around in the stack that change
-their visibility in the natural way (handling window overlaps). <P>
-
-Finally, this document describes in detail the <A HREF="#menu">menus</A> and <A
-HREF="#form">forms</A> extension libraries, also cloned from System V,
-which support easy construction and sequences of menus and fill-in
-forms.
-
-
-<H2><A NAME="terminology">Terminology</A></H2>
-
-In this document, the following terminology is used with reasonable
-consistency:
-
-<DL>
-<DT> window
-<DD>
-A data structure describing a sub-rectangle of the screen (possibly the
-entire screen). You can write to a window as though it were a miniature
-screen, scrolling independently of other windows on the physical screen.
-<DT> screens
-<DD>
-A subset of windows which are as large as the terminal screen, i.e., they start
-at the upper left hand corner and encompass the lower right hand corner. One
-of these, <CODE>stdscr</CODE>, is automatically provided for the programmer.
-<DT> terminal screen
-<DD>
-The package's idea of what the terminal display currently looks like, i.e.,
-what the user sees now. This is a special screen.
-</DL>
-
-<H1><A NAME="curses">The Curses Library</A></H1>
-
-<H2><A NAME="overview">An Overview of Curses</A></H2>
-
-<H3><A NAME="compiling">Compiling Programs using Curses</A></H3>
-
-In order to use the library, it is necessary to have certain types and
-variables defined. Therefore, the programmer must have a line:
-
-<PRE>
- #include <curses.h>
-</PRE>
-
-at the top of the program source. The screen package uses the Standard I/O
-library, so <CODE><curses.h></CODE> includes
-<CODE><stdio.h></CODE>. <CODE><curses.h></CODE> also includes
-<CODE><termios.h></CODE>, <CODE><termio.h></CODE>, or
-<CODE><sgtty.h></CODE> depending on your system. It is redundant (but
-harmless) for the programmer to do these includes, too. In linking with
-<CODE>curses</CODE> you need to have <CODE>-lncurses</CODE> in your LDFLAGS or on the
-command line. There is no need for any other libraries.
-
-<H3><A NAME="updating">Updating the Screen</A></H3>
-
-In order to update the screen optimally, it is necessary for the routines to
-know what the screen currently looks like and what the programmer wants it to
-look like next. For this purpose, a data type (structure) named WINDOW is
-defined which describes a window image to the routines, including its starting
-position on the screen (the (y, x) coordinates of the upper left hand corner)
-and its size. One of these (called <CODE>curscr</CODE>, for current screen) is a
-screen image of what the terminal currently looks like. Another screen (called
-<CODE>stdscr</CODE>, for standard screen) is provided by default to make changes
-on. <P>
-
-A window is a purely internal representation. It is used to build and store a
-potential image of a portion of the terminal. It doesn't bear any necessary
-relation to what is really on the terminal screen; it's more like a
-scratchpad or write buffer. <P>
-
-To make the section of physical screen corresponding to a window reflect the
-contents of the window structure, the routine <CODE>refresh()</CODE> (or
-<CODE>wrefresh()</CODE> if the window is not <CODE>stdscr</CODE>) is called. <P>
-
-A given physical screen section may be within the scope of any number of
-overlapping windows. Also, changes can be made to windows in any order,
-without regard to motion efficiency. Then, at will, the programmer can
-effectively say ``make it look like this,'' and let the package implementation
-determine the most efficient way to repaint the screen.
-
-<H3><A NAME="stdscr">Standard Windows and Function Naming Conventions</A></H3>
-
-As hinted above, the routines can use several windows, but two are
-automatically given: <CODE>curscr</CODE>, which knows what the terminal looks like,
-and <CODE>stdscr</CODE>, which is what the programmer wants the terminal to look
-like next. The user should never actually access <CODE>curscr</CODE> directly.
-Changes should be made to through the API, and then the routine
-<CODE>refresh()</CODE> (or <CODE>wrefresh()</CODE>) called. <P>
-
-Many functions are defined to use <CODE>stdscr</CODE> as a default screen. For
-example, to add a character to <CODE>stdscr</CODE>, one calls <CODE>addch()</CODE> with
-the desired character as argument. To write to a different window. use the
-routine <CODE>waddch()</CODE> (for `w'indow-specific addch()) is provided. This
-convention of prepending function names with a `w' when they are to be
-applied to specific windows is consistent. The only routines which do not
-follow it are those for which a window must always be specified. <P>
-
-In order to move the current (y, x) coordinates from one point to another, the
-routines <CODE>move()</CODE> and <CODE>wmove()</CODE> are provided. However, it is
-often desirable to first move and then perform some I/O operation. In order to
-avoid clumsiness, most I/O routines can be preceded by the prefix 'mv' and
-the desired (y, x) coordinates prepended to the arguments to the function. For
-example, the calls
-
-<PRE>
- move(y, x);
- addch(ch);
-</PRE>
-
-can be replaced by
-
-<PRE>
- mvaddch(y, x, ch);
-</PRE>
-
-and
-
-<PRE>
- wmove(win, y, x);
- waddch(win, ch);
-</PRE>
-
-can be replaced by
-
-<PRE>
- mvwaddch(win, y, x, ch);
-</PRE>
-
-Note that the window description pointer (win) comes before the added (y, x)
-coordinates. If a function requires a window pointer, it is always the first
-parameter passed.
-
-<H3><A NAME="variables">Variables</A></H3>
-
-The <CODE>curses</CODE> library sets some variables describing the terminal
-capabilities.
-
-<PRE>
- type name description
- ------------------------------------------------------------------
- int LINES number of lines on the terminal
- int COLS number of columns on the terminal
-</PRE>
-
-The <CODE>curses.h</CODE> also introduces some <CODE>#define</CODE> constants and types
-of general usefulness:
-
-<DL>
-<DT> <CODE>bool</CODE>
-<DD> boolean type, actually a `char' (e.g., <CODE>bool doneit;</CODE>)
-<DT> <CODE>TRUE</CODE>
-<DD> boolean `true' flag (1).
-<DT> <CODE>FALSE</CODE>
-<DD> boolean `false' flag (0).
-<DT> <CODE>ERR</CODE>
-<DD> error flag returned by routines on a failure (-1).
-<DT> <CODE>OK</CODE>
-<DD> error flag returned by routines when things go right.
-</DL>
-
-<H2><A NAME="using">Using the Library</A></H2>
-
-Now we describe how to actually use the screen package. In it, we assume all
-updating, reading, etc. is applied to <CODE>stdscr</CODE>. These instructions will
-work on any window, providing you change the function names and parameters as
-mentioned above. <P>
-
-Here is a sample program to motivate the discussion:
-
-<PRE>
-#include <curses.h>
-#include <signal.h>
-
-static void finish(int sig);
-
-int
-main(int argc, char *argv[])
-{
- int num = 0;
-
- /* initialize your non-curses data structures here */
-
- (void) signal(SIGINT, finish); /* arrange interrupts to terminate */
-
- (void) initscr(); /* initialize the curses library */
- keypad(stdscr, TRUE); /* enable keyboard mapping */
- (void) nonl(); /* tell curses not to do NL->CR/NL on output */
- (void) cbreak(); /* take input chars one at a time, no wait for \n */
- (void) echo(); /* echo input - in color */
-
- if (has_colors())
- {
- start_color();
-
- /*
- * Simple color assignment, often all we need. Color pair 0 cannot
- * be redefined. This example uses the same value for the color
- * pair as for the foreground color, though of course that is not
- * necessary:
- */
- init_pair(1, COLOR_RED, COLOR_BLACK);
- init_pair(2, COLOR_GREEN, COLOR_BLACK);
- init_pair(3, COLOR_YELLOW, COLOR_BLACK);
- init_pair(4, COLOR_BLUE, COLOR_BLACK);
- init_pair(5, COLOR_CYAN, COLOR_BLACK);
- init_pair(6, COLOR_MAGENTA, COLOR_BLACK);
- init_pair(7, COLOR_WHITE, COLOR_BLACK);
- }
-
- for (;;)
- {
- int c = getch(); /* refresh, accept single keystroke of input */
- attrset(COLOR_PAIR(num % 8));
- num++;
-
- /* process the command keystroke */
- }
-
- finish(0); /* we're done */
-}
-
-static void finish(int sig)
-{
- endwin();
-
- /* do your non-curses wrapup here */
-
- exit(0);
-}
-</PRE>
-
-<H3><A NAME="starting">Starting up</A></H3>
-
-In order to use the screen package, the routines must know about terminal
-characteristics, and the space for <CODE>curscr</CODE> and <CODE>stdscr</CODE> must be
-allocated. These function <CODE>initscr()</CODE> does both these things. Since it
-must allocate space for the windows, it can overflow memory when attempting to
-do so. On the rare occasions this happens, <CODE>initscr()</CODE> will terminate
-the program with an error message. <CODE>initscr()</CODE> must always be called
-before any of the routines which affect windows are used. If it is not, the
-program will core dump as soon as either <CODE>curscr</CODE> or <CODE>stdscr</CODE> are
-referenced. However, it is usually best to wait to call it until after you are
-sure you will need it, like after checking for startup errors. Terminal status
-changing routines like <CODE>nl()</CODE> and <CODE>cbreak()</CODE> should be called
-after <CODE>initscr()</CODE>. <P>
-
-Once the screen windows have been allocated, you can set them up for
-your program. If you want to, say, allow a screen to scroll, use
-<CODE>scrollok()</CODE>. If you want the cursor to be left in place after
-the last change, use <CODE>leaveok()</CODE>. If this isn't done,
-<CODE>refresh()</CODE> will move the cursor to the window's current (y, x)
-coordinates after updating it. <P>
-
-You can create new windows of your own using the functions <CODE>newwin()</CODE>,
-<CODE>derwin()</CODE>, and <CODE>subwin()</CODE>. The routine <CODE>delwin()</CODE> will
-allow you to get rid of old windows. All the options described above can be
-applied to any window.
-
-<H3><A NAME="output">Output</A></H3>
-
-Now that we have set things up, we will want to actually update the terminal.
-The basic functions used to change what will go on a window are
-<CODE>addch()</CODE> and <CODE>move()</CODE>. <CODE>addch()</CODE> adds a character at the
-current (y, x) coordinates. <CODE>move()</CODE> changes the current (y, x)
-coordinates to whatever you want them to be. It returns <CODE>ERR</CODE> if you
-try to move off the window. As mentioned above, you can combine the two into
-<CODE>mvaddch()</CODE> to do both things at once. <P>
-
-The other output functions, such as <CODE>addstr()</CODE> and <CODE>printw()</CODE>,
-all call <CODE>addch()</CODE> to add characters to the window. <P>
-
-After you have put on the window what you want there, when you want the portion
-of the terminal covered by the window to be made to look like it, you must call
-<CODE>refresh()</CODE>. In order to optimize finding changes, <CODE>refresh()</CODE>
-assumes that any part of the window not changed since the last
-<CODE>refresh()</CODE> of that window has not been changed on the terminal, i.e.,
-that you have not refreshed a portion of the terminal with an overlapping
-window. If this is not the case, the routine <CODE>touchwin()</CODE> is provided
-to make it look like the entire window has been changed, thus making
-<CODE>refresh()</CODE> check the whole subsection of the terminal for changes. <P>
-
-If you call <CODE>wrefresh()</CODE> with <CODE>curscr</CODE> as its argument, it will
-make the screen look like <CODE>curscr</CODE> thinks it looks like. This is useful
-for implementing a command which would redraw the screen in case it get messed
-up.
-
-<H3><A NAME="input">Input</A></H3>
-
-The complementary function to <CODE>addch()</CODE> is <CODE>getch()</CODE> which, if
-echo is set, will call <CODE>addch()</CODE> to echo the character. Since the
-screen package needs to know what is on the terminal at all times, if
-characters are to be echoed, the tty must be in raw or cbreak mode. Since
-initially the terminal has echoing enabled and is in ordinary ``cooked'' mode,
-one or the other has to changed before calling <CODE>getch()</CODE>; otherwise,
-the program's output will be unpredictable. <P>
-
-When you need to accept line-oriented input in a window, the functions
-<CODE>wgetstr()</CODE> and friends are available. There is even a <CODE>wscanw()</CODE>
-function that can do <CODE>scanf()</CODE>(3)-style multi-field parsing on window
-input. These pseudo-line-oriented functions turn on echoing while they
-execute. <P>
-
-The example code above uses the call <CODE>keypad(stdscr, TRUE)</CODE> to enable
-support for function-key mapping. With this feature, the <CODE>getch()</CODE> code
-watches the input stream for character sequences that correspond to arrow and
-function keys. These sequences are returned as pseudo-character values. The
-<CODE>#define</CODE> values returned are listed in the <CODE>curses.h</CODE> The
-mapping from sequences to <CODE>#define</CODE> values is determined by
-<CODE>key_</CODE> capabilities in the terminal's terminfo entry.
-
-<H3><A NAME="formschars">Using Forms Characters</A></H3>
-
-The <CODE>addch()</CODE> function (and some others, including <CODE>box()</CODE> and
-<CODE>border()</CODE>) can accept some pseudo-character arguments which are specially
-defined by <CODE>ncurses</CODE>. These are <CODE>#define</CODE> values set up in
-the <CODE>curses.h</CODE> header; see there for a complete list (look for
-the prefix <CODE>ACS_</CODE>). <P>
-
-The most useful of the ACS defines are the forms-drawing characters. You can
-use these to draw boxes and simple graphs on the screen. If the terminal
-does not have such characters, <CODE>curses.h</CODE> will map them to a
-recognizable (though ugly) set of ASCII defaults.
-
-<H3><A NAME="attributes">Character Attributes and Color</A></H3>
-
-The <CODE>ncurses</CODE> package supports screen highlights including standout,
-reverse-video, underline, and blink. It also supports color, which is treated
-as another kind of highlight. <P>
-
-Highlights are encoded, internally, as high bits of the pseudo-character type
-(<CODE>chtype</CODE>) that <CODE>curses.h</CODE> uses to represent the contents of a
-screen cell. See the <CODE>curses.h</CODE> header file for a complete list of
-highlight mask values (look for the prefix <CODE>A_</CODE>).<P>
-
-There are two ways to make highlights. One is to logical-or the value of the
-highlights you want into the character argument of an <CODE>addch()</CODE> call,
-or any other output call that takes a <CODE>chtype</CODE> argument. <P>
-
-The other is to set the current-highlight value. This is logical-or'ed with
-any highlight you specify the first way. You do this with the functions
-<CODE>attron()</CODE>, <CODE>attroff()</CODE>, and <CODE>attrset()</CODE>; see the manual
-pages for details.
-
-Color is a special kind of highlight. The package actually thinks in terms
-of color pairs, combinations of foreground and background colors. The sample
-code above sets up eight color pairs, all of the guaranteed-available colors
-on black. Note that each color pair is, in effect, given the name of its
-foreground color. Any other range of eight non-conflicting values could
-have been used as the first arguments of the <CODE>init_pair()</CODE> values. <P>
-
-Once you've done an <CODE>init_pair()</CODE> that creates color-pair N, you can
-use <CODE>COLOR_PAIR(N)</CODE> as a highlight that invokes that particular
-color combination. Note that <CODE>COLOR_PAIR(N)</CODE>, for constant N,
-is itself a compile-time constant and can be used in initializers.
-
-<H3><A NAME="mouse">Mouse Interfacing</A></H3>
-
-The <CODE>ncurses</CODE> library also provides a mouse interface.
-<!-- The 'note' tag is not portable enough -->
-<blockquote>
-<strong>NOTE:</strong> this facility is specific to <CODE>ncurses</CODE>, it is not part of either
-the XSI Curses standard, nor of System V Release 4, nor BSD curses.
-System V Release 4 curses contains code with similar interface definitions,
-however it is not documented. Other than by disassembling the library, we
-have no way to determine exactly how that mouse code works.
-Thus, we recommend that you wrap mouse-related code in an #ifdef using the
-feature macro NCURSES_MOUSE_VERSION so it will not be compiled and linked
-on non-ncurses systems.
-</blockquote>
-
-Presently, mouse event reporting works in the following environments:
-<ul>
-<li>xterm and similar programs such as rxvt.
-<li>Linux console, when configured with <CODE>gpm</CODE>(1), Alessandro
-Rubini's mouse server.
-<li>FreeBSD sysmouse (console)
-<li>OS/2 EMX
-</ul>
-<P>
-The mouse interface is very simple. To activate it, you use the function
-<CODE>mousemask()</CODE>, passing it as first argument a bit-mask that specifies
-what kinds of events you want your program to be able to see. It will
-return the bit-mask of events that actually become visible, which may differ
-from the argument if the mouse device is not capable of reporting some of
-the event types you specify. <P>
-
-Once the mouse is active, your application's command loop should watch
-for a return value of <CODE>KEY_MOUSE</CODE> from <CODE>wgetch()</CODE>. When
-you see this, a mouse event report has been queued. To pick it off
-the queue, use the function <CODE>getmouse()</CODE> (you must do this before
-the next <CODE>wgetch()</CODE>, otherwise another mouse event might come
-in and make the first one inaccessible). <P>
-
-Each call to <CODE>getmouse()</CODE> fills a structure (the address of which you'll
-pass it) with mouse event data. The event data includes zero-origin,
-screen-relative character-cell coordinates of the mouse pointer. It also
-includes an event mask. Bits in this mask will be set, corresponding
-to the event type being reported. <P>
-
-The mouse structure contains two additional fields which may be
-significant in the future as ncurses interfaces to new kinds of
-pointing device. In addition to x and y coordinates, there is a slot
-for a z coordinate; this might be useful with touch-screens that can
-return a pressure or duration parameter. There is also a device ID
-field, which could be used to distinguish between multiple pointing
-devices. <P>
-
-The class of visible events may be changed at any time via <CODE>mousemask()</CODE>.
-Events that can be reported include presses, releases, single-, double- and
-triple-clicks (you can set the maximum button-down time for clicks). If
-you don't make clicks visible, they will be reported as press-release
-pairs. In some environments, the event mask may include bits reporting
-the state of shift, alt, and ctrl keys on the keyboard during the event. <P>
-
-A function to check whether a mouse event fell within a given window is
-also supplied. You can use this to see whether a given window should
-consider a mouse event relevant to it. <P>
-
-Because mouse event reporting will not be available in all
-environments, it would be unwise to build <CODE>ncurses</CODE>
-applications that <EM>require</EM> the use of a mouse. Rather, you should
-use the mouse as a shortcut for point-and-shoot commands your application
-would normally accept from the keyboard. Two of the test games in the
-<CODE>ncurses</CODE> distribution (<CODE>bs</CODE> and <CODE>knight</CODE>) contain
-code that illustrates how this can be done. <P>
-
-See the manual page <CODE>curs_mouse(3X)</CODE> for full details of the
-mouse-interface functions.
-
-<H3><A NAME="finishing">Finishing Up</A></H3>
-
-In order to clean up after the <CODE>ncurses</CODE> routines, the routine
-<CODE>endwin()</CODE> is provided. It restores tty modes to what they were when
-<CODE>initscr()</CODE> was first called, and moves the cursor down to the
-lower-left corner. Thus, anytime after the call to initscr, <CODE>endwin()</CODE>
-should be called before exiting.
-
-<H2><A NAME="functions">Function Descriptions</A></H2>
-
-We describe the detailed behavior of some important curses functions here, as a
-supplement to the manual page descriptions.
-
-<H3><A NAME="init">Initialization and Wrapup</A></H3>
-
-<DL>
-<DT> <CODE>initscr()</CODE>
-<DD> The first function called should almost always be <CODE>initscr()</CODE>.
-This will determine the terminal type and
-initialize curses data structures. <CODE>initscr()</CODE> also arranges that
-the first call to <CODE>refresh()</CODE> will clear the screen. If an error
-occurs a message is written to standard error and the program
-exits. Otherwise it returns a pointer to stdscr. A few functions may be
-called before initscr (<CODE>slk_init()</CODE>, <CODE>filter()</CODE>,
-<CODE>ripoffline()</CODE>, <CODE>use_env()</CODE>, and, if you are using multiple
-terminals, <CODE>newterm()</CODE>.)
-<DT> <CODE>endwin()</CODE>
-<DD> Your program should always call <CODE>endwin()</CODE> before exiting or
-shelling out of the program. This function will restore tty modes,
-move the cursor to the lower left corner of the screen, reset the
-terminal into the proper non-visual mode. Calling <CODE>refresh()</CODE>
-or <CODE>doupdate()</CODE> after a temporary escape from the program will
-restore the ncurses screen from before the escape.
-<DT> <CODE>newterm(type, ofp, ifp)</CODE>
-<DD> A program which outputs to more than one terminal should use
-<CODE>newterm()</CODE> instead of <CODE>initscr()</CODE>. <CODE>newterm()</CODE> should
-be called once for each terminal. It returns a variable of type
-<CODE>SCREEN *</CODE> which should be saved as a reference to that
-terminal.
-(NOTE: a SCREEN variable is not a <em>screen</em> in the sense we
-are describing in this introduction, but a collection of
-parameters used to assist in optimizing the display.)
-The arguments are the type of the terminal (a string) and
-<CODE>FILE</CODE> pointers for the output and input of the terminal. If
-type is NULL then the environment variable <CODE>$TERM</CODE> is used.
-<CODE>endwin()</CODE> should called once at wrapup time for each terminal
-opened using this function.
-<DT> <CODE>set_term(new)</CODE>
-<DD> This function is used to switch to a different terminal previously
-opened by <CODE>newterm()</CODE>. The screen reference for the new terminal
-is passed as the parameter. The previous terminal is returned by the
-function. All other calls affect only the current terminal.
-<DT> <CODE>delscreen(sp)</CODE>
-<DD> The inverse of <CODE>newterm()</CODE>; deallocates the data structures
-associated with a given <CODE>SCREEN</CODE> reference.
-</DL>
-
-<H3><A NAME="flush">Causing Output to the Terminal</A></H3>
-
-<DL>
-<DT> <CODE>refresh()</CODE> and <CODE>wrefresh(win)</CODE>
-<DD> These functions must be called to actually get any output on
-the terminal, as other routines merely manipulate data
-structures. <CODE>wrefresh()</CODE> copies the named window to the physical
-terminal screen, taking into account what is already
-there in order to do optimizations. <CODE>refresh()</CODE> does a
-refresh of <CODE>stdscr</CODE>. Unless <CODE>leaveok()</CODE> has been
-enabled, the physical cursor of the terminal is left at the
-location of the window's cursor.
-<DT> <CODE>doupdate()</CODE> and <CODE>wnoutrefresh(win)</CODE>
-<DD> These two functions allow multiple updates with more efficiency
-than wrefresh. To use them, it is important to understand how curses
-works. In addition to all the window structures, curses keeps two
-data structures representing the terminal screen: a physical screen,
-describing what is actually on the screen, and a virtual screen,
-describing what the programmer wants to have on the screen. wrefresh
-works by first copying the named window to the virtual screen
-(<CODE>wnoutrefresh()</CODE>), and then calling the routine to update the
-screen (<CODE>doupdate()</CODE>). If the programmer wishes to output
-several windows at once, a series of calls to <CODE>wrefresh</CODE> will result
-in alternating calls to <CODE>wnoutrefresh()</CODE> and <CODE>doupdate()</CODE>,
-causing several bursts of output to the screen. By calling
-<CODE>wnoutrefresh()</CODE> for each window, it is then possible to call
-<CODE>doupdate()</CODE> once, resulting in only one burst of output, with
-fewer total characters transmitted (this also avoids a visually annoying
-flicker at each update).
-</DL>
-
-<H3><A NAME="lowlevel">Low-Level Capability Access</A></H3>
-
-<DL>
-<DT> <CODE>setupterm(term, filenum, errret)</CODE>
-<DD> This routine is called to initialize a terminal's description, without setting
-up the curses screen structures or changing the tty-driver mode bits.
-<CODE>term</CODE> is the character string representing the name of the terminal
-being used. <CODE>filenum</CODE> is the UNIX file descriptor of the terminal to
-be used for output. <CODE>errret</CODE> is a pointer to an integer, in which a
-success or failure indication is returned. The values returned can be 1 (all
-is well), 0 (no such terminal), or -1 (some problem locating the terminfo
-database). <P>
-
-The value of <CODE>term</CODE> can be given as NULL, which will cause the value of
-<CODE>TERM</CODE> in the environment to be used. The <CODE>errret</CODE> pointer can
-also be given as NULL, meaning no error code is wanted. If <CODE>errret</CODE> is
-defaulted, and something goes wrong, <CODE>setupterm()</CODE> will print an
-appropriate error message and exit, rather than returning. Thus, a simple
-program can call setupterm(0, 1, 0) and not worry about initialization
-errors. <P>
-
-After the call to <CODE>setupterm()</CODE>, the global variable <CODE>cur_term</CODE> is
-set to point to the current structure of terminal capabilities. By calling
-<CODE>setupterm()</CODE> for each terminal, and saving and restoring
-<CODE>cur_term</CODE>, it is possible for a program to use two or more terminals at
-once. <CODE>Setupterm()</CODE> also stores the names section of the terminal
-description in the global character array <CODE>ttytype[]</CODE>. Subsequent calls
-to <CODE>setupterm()</CODE> will overwrite this array, so you'll have to save it
-yourself if need be.
-</DL>
-
-<H3><A NAME="debugging">Debugging</A></H3>
-
-<!-- The 'note' tag is not portable enough -->
-<blockquote>
-<strong>NOTE:</strong> These functions are not part of the standard curses API!
-</blockquote>
-
-<DL>
-<DT> <CODE>trace()</CODE>
-<DD>
-This function can be used to explicitly set a trace level. If the
-trace level is nonzero, execution of your program will generate a file
-called `trace' in the current working directory containing a report on
-the library's actions. Higher trace levels enable more detailed (and
-verbose) reporting -- see comments attached to <CODE>TRACE_</CODE> defines
-in the <CODE>curses.h</CODE> file for details. (It is also possible to set
-a trace level by assigning a trace level value to the environment variable
-<CODE>NCURSES_TRACE</CODE>).
-<DT> <CODE>_tracef()</CODE>
-<DD>
-This function can be used to output your own debugging information. It is only
-available only if you link with -lncurses_g. It can be used the same way as
-<CODE>printf()</CODE>, only it outputs a newline after the end of arguments.
-The output goes to a file called <CODE>trace</CODE> in the current directory.
-</DL>
-
-Trace logs can be difficult to interpret due to the sheer volume of
-data dumped in them. There is a script called <STRONG>tracemunch</STRONG>
-included with the <CODE>ncurses</CODE> distribution that can alleviate
-this problem somewhat; it compacts long sequences of similar operations into
-more succinct single-line pseudo-operations. These pseudo-ops can be
-distinguished by the fact that they are named in capital letters.
-
-<H2><A NAME="hints">Hints, Tips, and Tricks</A></H2>
-
-The <CODE>ncurses</CODE> manual pages are a complete reference for this library.
-In the remainder of this document, we discuss various useful methods that
-may not be obvious from the manual page descriptions.
-
-<H3><A NAME="caution">Some Notes of Caution</A></H3>
-
-If you find yourself thinking you need to use <CODE>noraw()</CODE> or
-<CODE>nocbreak()</CODE>, think again and move carefully. It's probably
-better design to use <CODE>getstr()</CODE> or one of its relatives to
-simulate cooked mode. The <CODE>noraw()</CODE> and <CODE>nocbreak()</CODE>
-functions try to restore cooked mode, but they may end up clobbering
-some control bits set before you started your application. Also, they
-have always been poorly documented, and are likely to hurt your
-application's usability with other curses libraries. <P>
-
-Bear in mind that <CODE>refresh()</CODE> is a synonym for <CODE>wrefresh(stdscr)</CODE>.
-Don't try to mix use of <CODE>stdscr</CODE> with use of windows declared
-by <CODE>newwin()</CODE>; a <CODE>refresh()</CODE> call will blow them off the
-screen. The right way to handle this is to use <CODE>subwin()</CODE>, or
-not touch <CODE>stdscr</CODE> at all and tile your screen with declared
-windows which you then <CODE>wnoutrefresh()</CODE> somewhere in your program
-event loop, with a single <CODE>doupdate()</CODE> call to trigger actual
-repainting. <P>
-
-You are much less likely to run into problems if you design your screen
-layouts to use tiled rather than overlapping windows. Historically,
-curses support for overlapping windows has been weak, fragile, and poorly
-documented. The <CODE>ncurses</CODE> library is not yet an exception to this
-rule. <P>
-
-There is a panels library included in the <CODE>ncurses</CODE>
-distribution that does a pretty good job of strengthening the
-overlapping-windows facilities. <P>
-
-Try to avoid using the global variables LINES and COLS. Use
-<CODE>getmaxyx()</CODE> on the <CODE>stdscr</CODE> context instead. Reason:
-your code may be ported to run in an environment with window resizes,
-in which case several screens could be open with different sizes.
-
-<H3><A NAME="leaving">Temporarily Leaving NCURSES Mode</A></H3>
-
-Sometimes you will want to write a program that spends most of its time in
-screen mode, but occasionally returns to ordinary `cooked' mode. A common
-reason for this is to support shell-out. This behavior is simple to arrange
-in <CODE>ncurses</CODE>. <P>
-
-To leave <CODE>ncurses</CODE> mode, call <CODE>endwin()</CODE> as you would if you
-were intending to terminate the program. This will take the screen back to
-cooked mode; you can do your shell-out. When you want to return to
-<CODE>ncurses</CODE> mode, simply call <CODE>refresh()</CODE> or <CODE>doupdate()</CODE>.
-This will repaint the screen. <P>
-
-There is a boolean function, <CODE>isendwin()</CODE>, which code can use to
-test whether <CODE>ncurses</CODE> screen mode is active. It returns <CODE>TRUE</CODE>
-in the interval between an <CODE>endwin()</CODE> call and the following
-<CODE>refresh()</CODE>, <CODE>FALSE</CODE> otherwise. <P>
-
-Here is some sample code for shellout:
-
-<PRE>
- addstr("Shelling out...");
- def_prog_mode(); /* save current tty modes */
- endwin(); /* restore original tty modes */
- system("sh"); /* run shell */
- addstr("returned.\n"); /* prepare return message */
- refresh(); /* restore save modes, repaint screen */
-</PRE>
-
-<H3><A NAME="xterm">Using NCURSES under XTERM</A></H3>
-
-A resize operation in X sends <CODE>SIGWINCH</CODE> to the application running
-under xterm.
-
-The easiest way to handle <CODE>SIGWINCH</CODE>
-is to do an <CODE>endwin</CODE>,
-followed by an <CODE>refresh</CODE> and a screen repaint you code
-yourself.
-The <CODE>refresh</CODE> will pick up the new screen size from the
-xterm's environment. <P>
-
-That is the standard way, of course (it even works with some vendor's curses
-implementations).
-Its drawback is that it clears the screen to reinitialize the display, and does
-not resize subwindows which must be shrunk.
-<CODE>Ncurses</CODE> provides an extension which works better, the
-<CODE>resizeterm</CODE> function. That function ensures that all windows
-are limited to the new screen dimensions, and pads <CODE>stdscr</CODE>
-with blanks if the screen is larger. <P>
-
-The <CODE>ncurses</CODE> library provides a SIGWINCH signal handler,
-which pushes a <CODE>KEY_RESIZE</CODE> via the wgetch() calls.
-When <CODE>ncurses</CODE> returns that code,
-it calls <code>resizeterm</CODE>
-to update the size of the standard screen's window, repainting that
-(filling with blanks or truncating as needed).
-It also resizes other windows,
-but its effect may be less satisfactory because it cannot
-know how you want the screen re-painted.
-You will usually have to write special-purpose code to handle
-<CODE>KEY_RESIZE</CODE> yourself.
-
-<H3><A NAME="screens">Handling Multiple Terminal Screens</A></H3>
-
-The <CODE>initscr()</CODE> function actually calls a function named
-<CODE>newterm()</CODE> to do most of its work. If you are writing a program that
-opens multiple terminals, use <CODE>newterm()</CODE> directly. <P>
-
-For each call, you will have to specify a terminal type and a pair of file
-pointers; each call will return a screen reference, and <CODE>stdscr</CODE> will be
-set to the last one allocated. You will switch between screens with the
-<CODE>set_term</CODE> call. Note that you will also have to call
-<CODE>def_shell_mode</CODE> and <CODE>def_prog_mode</CODE> on each tty yourself.
-
-<H3><A NAME="testing">Testing for Terminal Capabilities</A></H3>
-
-Sometimes you may want to write programs that test for the presence of various
-capabilities before deciding whether to go into <CODE>ncurses</CODE> mode. An easy
-way to do this is to call <CODE>setupterm()</CODE>, then use the functions
-<CODE>tigetflag()</CODE>, <CODE>tigetnum()</CODE>, and <CODE>tigetstr()</CODE> to do your
-testing. <P>
-
-A particularly useful case of this often comes up when you want to
-test whether a given terminal type should be treated as `smart'
-(cursor-addressable) or `stupid'. The right way to test this is to see
-if the return value of <CODE>tigetstr("cup")</CODE> is non-NULL. Alternatively,
-you can include the <CODE>term.h</CODE> file and test the value of the
-macro <CODE>cursor_address</CODE>.
-
-<H3><A NAME="tuning">Tuning for Speed</A></H3>
-
-Use the <CODE>addchstr()</CODE> family of functions for fast
-screen-painting of text when you know the text doesn't contain any
-control characters. Try to make attribute changes infrequent on your
-screens. Don't use the <CODE>immedok()</CODE> option!
-
-<H3><A NAME="special">Special Features of NCURSES</A></H3>
-
-The <CODE>wresize()</CODE> function allows you to resize a window in place.
-The associated <CODE>resizeterm()</CODE> function simplifies the construction
-of <a HREF="#xterm">SIGWINCH</a> handlers, for resizing all windows. <P>
-
-The <CODE>define_key()</CODE> function allows you
-to define at runtime function-key control sequences which are not in the
-terminal description.
-The <CODE>keyok()</CODE> function allows you to temporarily
-enable or disable interpretation of any function-key control sequence. <P>
-
-The <CODE>use_default_colors()</CODE> function allows you to construct
-applications which can use the terminal's default foreground and
-background colors as an additional "default" color.
-Several terminal emulators support this feature, which is based on ISO 6429. <P>
-
-Ncurses supports up 16 colors, unlike SVr4 curses which defines only 8.
-While most terminals which provide color allow only 8 colors, about
-a quarter (including XFree86 xterm) support 16 colors.
-
-<H2><A NAME="compat">Compatibility with Older Versions</A></H2>
-
-Despite our best efforts, there are some differences between <CODE>ncurses</CODE>
-and the (undocumented!) behavior of older curses implementations. These arise
-from ambiguities or omissions in the documentation of the API.
-
-<H3><A NAME="refbug">Refresh of Overlapping Windows</A></H3>
-
-If you define two windows A and B that overlap, and then alternately scribble
-on and refresh them, the changes made to the overlapping region under historic
-<CODE>curses</CODE> versions were often not documented precisely. <P>
-
-To understand why this is a problem, remember that screen updates are
-calculated between two representations of the <EM>entire</EM> display. The
-documentation says that when you refresh a window, it is first copied to the
-virtual screen, and then changes are calculated to update the physical screen
-(and applied to the terminal). But "copied to" is not very specific, and
-subtle differences in how copying works can produce different behaviors in the
-case where two overlapping windows are each being refreshed at unpredictable
-intervals. <P>
-
-What happens to the overlapping region depends on what <CODE>wnoutrefresh()</CODE>
-does with its argument -- what portions of the argument window it copies to the
-virtual screen. Some implementations do "change copy", copying down only
-locations in the window that have changed (or been marked changed with
-<CODE>wtouchln()</CODE> and friends). Some implementations do "entire copy",
-copying <EM>all</EM> window locations to the virtual screen whether or not
-they have changed. <P>
-
-The <CODE>ncurses</CODE> library itself has not always been consistent on this
-score. Due to a bug, versions 1.8.7 to 1.9.8a did entire copy. Versions
-1.8.6 and older, and versions 1.9.9 and newer, do change copy. <P>
-
-For most commercial curses implementations, it is not documented and not known
-for sure (at least not to the <CODE>ncurses</CODE> maintainers) whether they do
-change copy or entire copy. We know that System V release 3 curses has logic
-in it that looks like an attempt to do change copy, but the surrounding logic
-and data representations are sufficiently complex, and our knowledge
-sufficiently indirect, that it's hard to know whether this is reliable.
-
-It is not clear what the SVr4 documentation and XSI standard intend. The XSI
-Curses standard barely mentions wnoutrefresh(); the SVr4 documents seem to be
-describing entire-copy, but it is possible with some effort and straining to
-read them the other way. <P>
-
-It might therefore be unwise to rely on either behavior in programs that might
-have to be linked with other curses implementations. Instead, you can do an
-explicit <CODE>touchwin()</CODE> before the <CODE>wnoutrefresh()</CODE> call to
-guarantee an entire-contents copy anywhere. <P>
-
-The really clean way to handle this is to use the panels library. If,
-when you want a screen update, you do <CODE>update_panels()</CODE>, it will
-do all the necessary <CODE>wnoutrefresh()</CODE> calls for whatever panel
-stacking order you have defined. Then you can do one <CODE>doupdate()</CODE>
-and there will be a <EM>single</EM> burst of physical I/O that will do
-all your updates.
-
-<H3><A NAME="backbug">Background Erase</A></H3>
-
-If you have been using a very old versions of <CODE>ncurses</CODE> (1.8.7 or
-older) you may be surprised by the behavior of the erase functions. In older
-versions, erased areas of a window were filled with a blank modified by the
-window's current attribute (as set by <STRONG>wattrset()</STRONG>, <STRONG>wattron()</STRONG>,
-<STRONG>wattroff()</STRONG> and friends). <P>
-
-In newer versions, this is not so. Instead, the attribute of erased blanks
-is normal unless and until it is modified by the functions <CODE>bkgdset()</CODE>
-or <CODE>wbkgdset()</CODE>. <P>
-
-This change in behavior conforms <CODE>ncurses</CODE> to System V Release 4 and
-the XSI Curses standard.
-
-<H2><A NAME="xsifuncs">XSI Curses Conformance</A></H2>
-
-The <CODE>ncurses</CODE> library is intended to be base-level conformant with the
-XSI Curses standard from X/Open. Many extended-level features (in fact, almost
-all features not directly concerned with wide characters and
-internationalization) are also supported. <P>
-
-One effect of XSI conformance is the change in behavior described under
-<A HREF="#backbug">"Background Erase -- Compatibility with Old Versions"</A>. <P>
-
-Also, <CODE>ncurses</CODE> meets the XSI requirement that every macro
-entry point have a corresponding function which may be linked (and
-will be prototype-checked) if the macro definition is disabled with
-<CODE>#undef</CODE>.
-
-<H1><A NAME="panels">The Panels Library</A></H1>
-
-The <CODE>ncurses</CODE> library by itself provides good support for screen
-displays in which the windows are tiled (non-overlapping). In the more
-general case that windows may overlap, you have to use a series of
-<CODE>wnoutrefresh()</CODE> calls followed by a <CODE>doupdate()</CODE>, and be
-careful about the order you do the window refreshes in. It has to be
-bottom-upwards, otherwise parts of windows that should be obscured will
-show through. <P>
-
-When your interface design is such that windows may dive deeper into the
-visibility stack or pop to the top at runtime, the resulting book-keeping
-can be tedious and difficult to get right. Hence the panels library. <P>
-
-The <CODE>panel</CODE> library first appeared in AT&T System V. The
-version documented here is the <CODE>panel</CODE> code distributed
-with <CODE>ncurses</CODE>.
-
-<H2><A NAME="pcompile">Compiling With the Panels Library</A></H2>
-
-Your panels-using modules must import the panels library declarations with
-
-<PRE>
- #include <panel.h>
-</PRE>
-
-and must be linked explicitly with the panels library using an
-<CODE>-lpanel</CODE> argument. Note that they must also link the
-<CODE>ncurses</CODE> library with <CODE>-lncurses</CODE>. Many linkers
-are two-pass and will accept either order, but it is still good practice
-to put <CODE>-lpanel</CODE> first and <CODE>-lncurses</CODE> second.
-
-<H2><A NAME="poverview">Overview of Panels</A></H2>
-
-A panel object is a window that is implicitly treated as part of a
-<DFN>deck</DFN> including all other panel objects. The deck has an implicit
-bottom-to-top visibility order. The panels library includes an update
-function (analogous to <CODE>refresh()</CODE>) that displays all panels in the
-deck in the proper order to resolve overlaps. The standard window,
-<CODE>stdscr</CODE>, is considered below all panels. <P>
-
-Details on the panels functions are available in the man pages. We'll just
-hit the highlights here. <P>
-
-You create a panel from a window by calling <CODE>new_panel()</CODE> on a
-window pointer. It then becomes the top of the deck. The panel's window
-is available as the value of <CODE>panel_window()</CODE> called with the
-panel pointer as argument.<P>
-
-You can delete a panel (removing it from the deck) with <CODE>del_panel</CODE>.
-This will not deallocate the associated window; you have to do that yourself.
-
-You can replace a panel's window with a different window by calling
-<CODE>replace_window</CODE>. The new window may be of different size;
-the panel code will re-compute all overlaps. This operation doesn't
-change the panel's position in the deck. <P>
-
-To move a panel's window, use <CODE>move_panel()</CODE>. The
-<CODE>mvwin()</CODE> function on the panel's window isn't sufficient because it
-doesn't update the panels library's representation of where the windows are.
-This operation leaves the panel's depth, contents, and size unchanged. <P>
-
-Two functions (<CODE>top_panel()</CODE>, <CODE>bottom_panel()</CODE>) are
-provided for rearranging the deck. The first pops its argument window to the
-top of the deck; the second sends it to the bottom. Either operation leaves
-the panel's screen location, contents, and size unchanged. <P>
-
-The function <CODE>update_panels()</CODE> does all the
-<CODE>wnoutrefresh()</CODE> calls needed to prepare for
-<CODE>doupdate()</CODE> (which you must call yourself, afterwards). <P>
-
-Typically, you will want to call <CODE>update_panels()</CODE> and
-<CODE>doupdate()</CODE> just before accepting command input, once in each cycle
-of interaction with the user. If you call <CODE>update_panels()</CODE> after
-each and every panel write, you'll generate a lot of unnecessary refresh
-activity and screen flicker.
-
-<H2><A NAME="pstdscr">Panels, Input, and the Standard Screen</A></H2>
-
-You shouldn't mix <CODE>wnoutrefresh()</CODE> or <CODE>wrefresh()</CODE>
-operations with panels code; this will work only if the argument window
-is either in the top panel or unobscured by any other panels. <P>
-
-The <CODE>stsdcr</CODE> window is a special case. It is considered below all
-panels. Because changes to panels may obscure parts of <CODE>stdscr</CODE>,
-though, you should call <CODE>update_panels()</CODE> before
-<CODE>doupdate()</CODE> even when you only change <CODE>stdscr</CODE>. <P>
-
-Note that <CODE>wgetch</CODE> automatically calls <CODE>wrefresh</CODE>.
-Therefore, before requesting input from a panel window, you need to be sure
-that the panel is totally unobscured. <P>
-
-There is presently no way to display changes to one obscured panel without
-repainting all panels.
-
-<H2><A NAME="hiding">Hiding Panels</A></H2>
-
-It's possible to remove a panel from the deck temporarily; use
-<CODE>hide_panel</CODE> for this. Use <CODE>show_panel()</CODE> to render it
-visible again. The predicate function <CODE>panel_hidden</CODE>
-tests whether or not a panel is hidden. <P>
-
-The <CODE>panel_update</CODE> code ignores hidden panels. You cannot do
-<CODE>top_panel()</CODE> or <CODE>bottom_panel</CODE> on a hidden panel().
-Other panels operations are applicable.
-
-<H2><A NAME="pmisc">Miscellaneous Other Facilities</A></H2>
-
-It's possible to navigate the deck using the functions
-<CODE>panel_above()</CODE> and <CODE>panel_below</CODE>. Handed a panel
-pointer, they return the panel above or below that panel. Handed
-<CODE>NULL</CODE>, they return the bottom-most or top-most panel. <P>
-
-Every panel has an associated user pointer, not used by the panel code, to
-which you can attach application data. See the man page documentation
-of <CODE>set_panel_userptr()</CODE> and <CODE>panel_userptr</CODE> for
-details.
-
-<H1><A NAME="menu">The Menu Library</A></H1>
-
-A menu is a screen display that assists the user to choose some subset
-of a given set of items. The <CODE>menu</CODE> library is a curses
-extension that supports easy programming of menu hierarchies with a
-uniform but flexible interface. <P>
-
-The <CODE>menu</CODE> library first appeared in AT&T System V. The
-version documented here is the <CODE>menu</CODE> code distributed
-with <CODE>ncurses</CODE>.
-
-<H2><A NAME="mcompile">Compiling With the menu Library</A></H2>
-
-Your menu-using modules must import the menu library declarations with
-
-<PRE>
- #include <menu.h>
-</PRE>
-
-and must be linked explicitly with the menus library using an
-<CODE>-lmenu</CODE> argument. Note that they must also link the
-<CODE>ncurses</CODE> library with <CODE>-lncurses</CODE>. Many linkers
-are two-pass and will accept either order, but it is still good practice
-to put <CODE>-lmenu</CODE> first and <CODE>-lncurses</CODE> second.
-
-<H2><A NAME="moverview">Overview of Menus</A></H2>
-
-The menus created by this library consist of collections of
-<DFN>items</DFN> including a name string part and a description string
-part. To make menus, you create groups of these items and connect
-them with menu frame objects. <P>
-
-The menu can then by <DFN>posted</DFN>, that is written to an
-associated window. Actually, each menu has two associated windows; a
-containing window in which the programmer can scribble titles or
-borders, and a subwindow in which the menu items proper are displayed.
-If this subwindow is too small to display all the items, it will be a
-scrollable viewport on the collection of items. <P>
-
-A menu may also be <DFN>unposted</DFN> (that is, undisplayed), and finally
-freed to make the storage associated with it and its items available for
-re-use. <P>
-
-The general flow of control of a menu program looks like this:
-
-<OL>
-<LI>Initialize <CODE>curses</CODE>.
-<LI>Create the menu items, using <CODE>new_item()</CODE>.
-<LI>Create the menu using <CODE>new_menu()</CODE>.
-<LI>Post the menu using <CODE>post_menu()</CODE>.
-<LI>Refresh the screen.
-<LI>Process user requests via an input loop.
-<LI>Unpost the menu using <CODE>unpost_menu()</CODE>.
-<LI>Free the menu, using <CODE>free_menu()</CODE>.
-<LI>Free the items using <CODE>free_item()</CODE>.
-<LI>Terminate <CODE>curses</CODE>.
-</OL>
-
-<H2><A NAME="mselect">Selecting items</A></H2>
-
-Menus may be multi-valued or (the default) single-valued (see the manual
-page <CODE>menu_opts(3x)</CODE> to see how to change the default).
-Both types always have a <DFN>current item</DFN>. <P>
-
-From a single-valued menu you can read the selected value simply by looking
-at the current item. From a multi-valued menu, you get the selected set
-by looping through the items applying the <CODE>item_value()</CODE>
-predicate function. Your menu-processing code can use the function
-<CODE>set_item_value()</CODE> to flag the items in the select set. <P>
-
-Menu items can be made unselectable using <CODE>set_item_opts()</CODE>
-or <CODE>item_opts_off()</CODE> with the <CODE>O_SELECTABLE</CODE>
-argument. This is the only option so far defined for menus, but it
-is good practice to code as though other option bits might be on.
-
-<H2><A NAME="mdisplay">Menu Display</A></H2>
-
-The menu library calculates a minimum display size for your window, based
-on the following variables:
-
-<UL>
-<LI>The number and maximum length of the menu items
-<LI>Whether the O_ROWMAJOR option is enabled
-<LI>Whether display of descriptions is enabled
-<LI>Whatever menu format may have been set by the programmer
-<LI>The length of the menu mark string used for highlighting selected items
-</UL>
-
-The function <CODE>set_menu_format()</CODE> allows you to set the
-maximum size of the viewport or <DFN>menu page</DFN> that will be used
-to display menu items. You can retrieve any format associated with a
-menu with <CODE>menu_format()</CODE>. The default format is rows=16,
-columns=1. <P>
-
-The actual menu page may be smaller than the format size. This depends
-on the item number and size and whether O_ROWMAJOR is on. This option
-(on by default) causes menu items to be displayed in a `raster-scan'
-pattern, so that if more than one item will fit horizontally the first
-couple of items are side-by-side in the top row. The alternative is
-column-major display, which tries to put the first several items in
-the first column. <P>
-
-As mentioned above, a menu format not large enough to allow all items to fit
-on-screen will result in a menu display that is vertically scrollable. <P>
-You can scroll it with requests to the menu driver, which will be described
-in the section on <A HREF="#minput">menu input handling</A>. <P>
-
-Each menu has a <DFN>mark string</DFN> used to visually tag selected items;
-see the <CODE>menu_mark(3x)</CODE> manual page for details. The mark
-string length also influences the menu page size. <P>
-
-The function <CODE>scale_menu()</CODE> returns the minimum display size
-that the menu code computes from all these factors.
-
-There are other menu display attributes including a select attribute,
-an attribute for selectable items, an attribute for unselectable items,
-and a pad character used to separate item name text from description
-text. These have reasonable defaults which the library allows you to
-change (see the <CODE>menu_attribs(3x)</CODE> manual page.
-
-<H2><A NAME="mwindows">Menu Windows</A></H2>
-
-Each menu has, as mentioned previously, a pair of associated windows.
-Both these windows are painted when the menu is posted and erased when
-the menu is unposted. <P>
-
-The outer or frame window is not otherwise touched by the menu
-routines. It exists so the programmer can associate a title, a
-border, or perhaps help text with the menu and have it properly
-refreshed or erased at post/unpost time. The inner window or
-<DFN>subwindow</DFN> is where the current menu page is displayed. <P>
-
-By default, both windows are <CODE>stdscr</CODE>. You can set them with the
-functions in <CODE>menu_win(3x)</CODE>. <P>
-
-When you call <CODE>post_menu()</CODE>, you write the menu to its
-subwindow. When you call <CODE>unpost_menu()</CODE>, you erase the
-subwindow, However, neither of these actually modifies the screen. To
-do that, call <CODE>wrefresh()</CODE> or some equivalent.
-
-<H2><A NAME="minput">Processing Menu Input</A></H2>
-
-The main loop of your menu-processing code should call
-<CODE>menu_driver()</CODE> repeatedly. The first argument of this routine
-is a menu pointer; the second is a menu command code. You should write an
-input-fetching routine that maps input characters to menu command codes, and
-pass its output to <CODE>menu_driver()</CODE>. The menu command codes are
-fully documented in <CODE>menu_driver(3x)</CODE>. <P>
-
-The simplest group of command codes is <CODE>REQ_NEXT_ITEM</CODE>,
-<CODE>REQ_PREV_ITEM</CODE>, <CODE>REQ_FIRST_ITEM</CODE>,
-<CODE>REQ_LAST_ITEM</CODE>, <CODE>REQ_UP_ITEM</CODE>,
-<CODE>REQ_DOWN_ITEM</CODE>, <CODE>REQ_LEFT_ITEM</CODE>,
-<CODE>REQ_RIGHT_ITEM</CODE>. These change the currently selected
-item. These requests may cause scrolling of the menu page if it only
-partially displayed. <P>
-
-There are explicit requests for scrolling which also change the
-current item (because the select location does not change, but the
-item there does). These are <CODE>REQ_SCR_DLINE</CODE>,
-<CODE>REQ_SCR_ULINE</CODE>, <CODE>REQ_SCR_DPAGE</CODE>, and
-<CODE>REQ_SCR_UPAGE</CODE>. <P>
-
-The <CODE>REQ_TOGGLE_ITEM</CODE> selects or deselects the current item.
-It is for use in multi-valued menus; if you use it with <CODE>O_ONEVALUE</CODE>
-on, you'll get an error return (<CODE>E_REQUEST_DENIED</CODE>). <P>
-
-Each menu has an associated pattern buffer. The
-<CODE>menu_driver()</CODE> logic tries to accumulate printable ASCII
-characters passed in in that buffer; when it matches a prefix of an
-item name, that item (or the next matching item) is selected. If
-appending a character yields no new match, that character is deleted
-from the pattern buffer, and <CODE>menu_driver()</CODE> returns
-<CODE>E_NO_MATCH</CODE>. <P>
-
-Some requests change the pattern buffer directly:
-<CODE>REQ_CLEAR_PATTERN</CODE>, <CODE>REQ_BACK_PATTERN</CODE>,
-<CODE>REQ_NEXT_MATCH</CODE>, <CODE>REQ_PREV_MATCH</CODE>. The latter
-two are useful when pattern buffer input matches more than one item
-in a multi-valued menu. <P>
-
-Each successful scroll or item navigation request clears the pattern
-buffer. It is also possible to set the pattern buffer explicitly
-with <CODE>set_menu_pattern()</CODE>. <P>
-
-Finally, menu driver requests above the constant <CODE>MAX_COMMAND</CODE>
-are considered application-specific commands. The <CODE>menu_driver()</CODE>
-code ignores them and returns <CODE>E_UNKNOWN_COMMAND</CODE>.
-
-<H2><A NAME="mmisc">Miscellaneous Other Features</A></H2>
-
-Various menu options can affect the processing and visual appearance
-and input processing of menus. See <CODE>menu_opts(3x) for
-details.</CODE> <P>
-
-It is possible to change the current item from application code; this
-is useful if you want to write your own navigation requests. It is
-also possible to explicitly set the top row of the menu display. See
-<CODE>mitem_current(3x)</CODE>.
-
-If your application needs to change the menu subwindow cursor for
-any reason, <CODE>pos_menu_cursor()</CODE> will restore it to the
-correct location for continuing menu driver processing. <P>
-
-It is possible to set hooks to be called at menu initialization and
-wrapup time, and whenever the selected item changes. See
-<CODE>menu_hook(3x)</CODE>. <P>
-
-Each item, and each menu, has an associated user pointer on which you
-can hang application data. See <CODE>mitem_userptr(3x)</CODE> and
-<CODE>menu_userptr(3x)</CODE>.
-
-<H1><A NAME="form">The Forms Library</A></H1>
-
-The <CODE>form</CODE> library is a curses extension that supports easy
-programming of on-screen forms for data entry and program control. <P>
-
-The <CODE>form</CODE> library first appeared in AT&T System V. The
-version documented here is the <CODE>form</CODE> code distributed
-with <CODE>ncurses</CODE>.
-
-<H2><A NAME="fcompile">Compiling With the form Library</A></H2>
-
-Your form-using modules must import the form library declarations with
-
-<PRE>
- #include <form.h>
-</PRE>
-
-and must be linked explicitly with the forms library using an
-<CODE>-lform</CODE> argument. Note that they must also link the
-<CODE>ncurses</CODE> library with <CODE>-lncurses</CODE>. Many linkers
-are two-pass and will accept either order, but it is still good practice
-to put <CODE>-lform</CODE> first and <CODE>-lncurses</CODE> second.
-
-<H2><A NAME="foverview">Overview of Forms</A></H2>
-
-A form is a collection of fields; each field may be either a label
-(explanatory text) or a data-entry location. Long forms may be
-segmented into pages; each entry to a new page clears the screen. <P>
-To make forms, you create groups of fields and connect them with form
-frame objects; the form library makes this relatively simple. <P>
-
-Once defined, a form can be <DFN>posted</DFN>, that is written to an
-associated window. Actually, each form has two associated windows; a
-containing window in which the programmer can scribble titles or
-borders, and a subwindow in which the form fields proper are displayed. <P>
-
-As the form user fills out the posted form, navigation and editing
-keys support movement between fields, editing keys support modifying
-field, and plain text adds to or changes data in a current field. The
-form library allows you (the forms designer) to bind each navigation
-and editing key to any keystroke accepted by <CODE>curses</CODE>
-
-Fields may have validation conditions on them, so that they check input
-data for type and value. The form library supplies a rich set of
-pre-defined field types, and makes it relatively easy to define new ones. <P>
-
-Once its transaction is completed (or aborted), a form may be
-<DFN>unposted</DFN> (that is, undisplayed), and finally freed to make
-the storage associated with it and its items available for re-use. <P>
-
-The general flow of control of a form program looks like this:
-
-<OL>
-<LI>Initialize <CODE>curses</CODE>.
-<LI>Create the form fields, using <CODE>new_field()</CODE>.
-<LI>Create the form using <CODE>new_form()</CODE>.
-<LI>Post the form using <CODE>post_form()</CODE>.
-<LI>Refresh the screen.
-<LI>Process user requests via an input loop.
-<LI>Unpost the form using <CODE>unpost_form()</CODE>.
-<LI>Free the form, using <CODE>free_form()</CODE>.
-<LI>Free the fields using <CODE>free_field()</CODE>.
-<LI>Terminate <CODE>curses</CODE>.
-</OL>
-
-Note that this looks much like a menu program; the form library handles
-tasks which are in many ways similar, and its interface was obviously
-designed to resemble that of the <A HREF="#menu">menu library</A>
-wherever possible. <P>
-
-In forms programs, however, the `process user requests' is somewhat more
-complicated than for menus. Besides menu-like navigation operations,
-the menu driver loop has to support field editing and data validation.
-
-<H2><A NAME="fcreate">Creating and Freeing Fields and Forms</A></H2>
-
-The basic function for creating fields is <CODE>new_field()</CODE>:
-
-<PRE>
-FIELD *new_field(int height, int width, /* new field size */
- int top, int left, /* upper left corner */
- int offscreen, /* number of offscreen rows */
- int nbuf); /* number of working buffers */
-</PRE>
-
-Menu items always occupy a single row, but forms fields may have
-multiple rows. So <CODE>new_field()</CODE> requires you to specify a
-width and height (the first two arguments, which mist both be greater
-than zero). <P>
-
-You must also specify the location of the field's upper left corner on
-the screen (the third and fourth arguments, which must be zero or
-greater). Note that these coordinates are relative to the form
-subwindow, which will coincide with <CODE>stdscr</CODE> by default but
-need not be <CODE>stdscr</CODE> if you've done an explicit
-<CODE>set_form_win()</CODE> call. <P>
-
-The fifth argument allows you to specify a number of off-screen rows. If
-this is zero, the entire field will always be displayed. If it is
-nonzero, the form will be scrollable, with only one screen-full (initially
-the top part) displayed at any given time. If you make a field dynamic
-and grow it so it will no longer fit on the screen, the form will become
-scrollable even if the <CODE>offscreen</CODE> argument was initially zero. <P>
-
-The forms library allocates one working buffer per field; the size of
-each buffer is <CODE>((height + offscreen)*width + 1</CODE>, one character
-for each position in the field plus a NUL terminator. The sixth
-argument is the number of additional data buffers to allocate for the
-field; your application can use them for its own purposes.
-
-<PRE>
-FIELD *dup_field(FIELD *field, /* field to copy */
- int top, int left); /* location of new copy */
-</PRE>
-
-The function <CODE>dup_field()</CODE> duplicates an existing field at a
-new location. Size and buffering information are copied; some
-attribute flags and status bits are not (see the
-<CODE>form_field_new(3X)</CODE> for details).
-
-<PRE>
-FIELD *link_field(FIELD *field, /* field to copy */
- int top, int left); /* location of new copy */
-</PRE>
-
-The function <CODE>link_field()</CODE> also duplicates an existing field
-at a new location. The difference from <CODE>dup_field()</CODE> is that
-it arranges for the new field's buffer to be shared with the old one. <P>
-
-Besides the obvious use in making a field editable from two different
-form pages, linked fields give you a way to hack in dynamic labels. If
-you declare several fields linked to an original, and then make them
-inactive, changes from the original will still be propagated to the
-linked fields. <P>
-
-As with duplicated fields, linked fields have attribute bits separate
-from the original. <P>
-
-As you might guess, all these field-allocations return <CODE>NULL</CODE> if
-the field allocation is not possible due to an out-of-memory error or
-out-of-bounds arguments. <P>
-
-To connect fields to a form, use
-
-<PRE>
-FORM *new_form(FIELD **fields);
-</PRE>
-
-This function expects to see a NULL-terminated array of field pointers.
-Said fields are connected to a newly-allocated form object; its address
-is returned (or else NULL if the allocation fails). <P>
-
-Note that <CODE>new_field()</CODE> does <EM>not</EM> copy the pointer array
-into private storage; if you modify the contents of the pointer array
-during forms processing, all manner of bizarre things might happen. Also
-note that any given field may only be connected to one form. <P>
-
-The functions <CODE>free_field()</CODE> and <CODE>free_form</CODE> are available
-to free field and form objects. It is an error to attempt to free a field
-connected to a form, but not vice-versa; thus, you will generally free
-your form objects first.
-
-<H2><A NAME="fattributes">Fetching and Changing Field Attributes</A></H2>
-
-Each form field has a number of location and size attributes
-associated with it. There are other field attributes used to control
-display and editing of the field. Some (for example, the <CODE>O_STATIC</CODE> bit)
-involve sufficient complications to be covered in sections of their own
-later on. We cover the functions used to get and set several basic
-attributes here. <P>
-
-When a field is created, the attributes not specified by the
-<CODE>new_field</CODE> function are copied from an invisible system
-default field. In attribute-setting and -fetching functions, the
-argument NULL is taken to mean this field. Changes to it persist
-as defaults until your forms application terminates.
-
-<H3><A NAME="fsizes">Fetching Size and Location Data</A></H3>
-
-You can retrieve field sizes and locations through:
-
-<PRE>
-int field_info(FIELD *field, /* field from which to fetch */
- int *height, *int width, /* field size */
- int *top, int *left, /* upper left corner */
- int *offscreen, /* number of offscreen rows */
- int *nbuf); /* number of working buffers */
-</PRE>
-
-This function is a sort of inverse of <CODE>new_field()</CODE>; instead of
-setting size and location attributes of a new field, it fetches them
-from an existing one.
-
-<H3><A NAME="flocation">Changing the Field Location</A></H3>
-
-It is possible to move a field's location on the screen:
-
-<PRE>
-int move_field(FIELD *field, /* field to alter */
- int top, int left); /* new upper-left corner */
-</PRE>
-
-You can, of course. query the current location through <CODE>field_info()</CODE>.
-
-<H3><A NAME="fjust">The Justification Attribute</A></H3>
-
-One-line fields may be unjustified, justified right, justified left,
-or centered. Here is how you manipulate this attribute:
-
-<PRE>
-int set_field_just(FIELD *field, /* field to alter */
- int justmode); /* mode to set */
-
-int field_just(FIELD *field); /* fetch mode of field */
-</PRE>
-
-The mode values accepted and returned by this functions are
-preprocessor macros <CODE>NO_JUSTIFICATION</CODE>, <CODE>JUSTIFY_RIGHT</CODE>,
-<CODE>JUSTIFY_LEFT</CODE>, or <CODE>JUSTIFY_CENTER</CODE>.
-
-<H3><A NAME="fdispatts">Field Display Attributes</A></H3>
-
-For each field, you can set a foreground attribute for entered
-characters, a background attribute for the entire field, and a pad
-character for the unfilled portion of the field. You can also
-control pagination of the form. <P>
-
-This group of four field attributes controls the visual appearance
-of the field on the screen, without affecting in any way the data
-in the field buffer.
-
-<PRE>
-int set_field_fore(FIELD *field, /* field to alter */
- chtype attr); /* attribute to set */
-
-chtype field_fore(FIELD *field); /* field to query */
-
-int set_field_back(FIELD *field, /* field to alter */
- chtype attr); /* attribute to set */
-
-chtype field_back(FIELD *field); /* field to query */
-
-int set_field_pad(FIELD *field, /* field to alter */
- int pad); /* pad character to set */
-
-chtype field_pad(FIELD *field);
-
-int set_new_page(FIELD *field, /* field to alter */
- int flag); /* TRUE to force new page */
-
-chtype new_page(FIELD *field); /* field to query */
-</PRE>
-
-The attributes set and returned by the first four functions are normal
-<CODE>curses(3x)</CODE> display attribute values (<CODE>A_STANDOUT</CODE>,
-<CODE>A_BOLD</CODE>, <CODE>A_REVERSE</CODE> etc).
-
-The page bit of a field controls whether it is displayed at the start of
-a new form screen.
-
-<H3><A NAME="foptions">Field Option Bits</A></H3>
-
-There is also a large collection of field option bits you can set to control
-various aspects of forms processing. You can manipulate them with these
-functions:
-
-<PRE>
-int set_field_opts(FIELD *field, /* field to alter */
- int attr); /* attribute to set */
-
-int field_opts_on(FIELD *field, /* field to alter */
- int attr); /* attributes to turn on */
-
-int field_opts_off(FIELD *field, /* field to alter */
- int attr); /* attributes to turn off */
-
-int field_opts(FIELD *field); /* field to query */
-</PRE>
-
-By default, all options are on. Here are the available option bits:
-<DL>
-<DT> O_VISIBLE
-<DD> Controls whether the field is visible on the screen. Can be used
-during form processing to hide or pop up fields depending on the value
-of parent fields.
-<DT> O_ACTIVE
-<DD> Controls whether the field is active during forms processing (i.e.
-visited by form navigation keys). Can be used to make labels or derived
-fields with buffer values alterable by the forms application, not the user.
-<DT> O_PUBLIC
-<DD> Controls whether data is displayed during field entry. If this option is
-turned off on a field, the library will accept and edit data in that field,
-but it will not be displayed and the visible field cursor will not move.
-You can turn off the O_PUBLIC bit to define password fields.
-<DT> O_EDIT
-<DD> Controls whether the field's data can be modified. When this option is
-off, all editing requests except <CODE>REQ_PREV_CHOICE</CODE> and
-<CODE>REQ_NEXT_CHOICE</CODE> will fail. Such read-only fields may be useful for
-help messages.
-<DT> O_WRAP
-<DD> Controls word-wrapping in multi-line fields. Normally, when any
-character of a (blank-separated) word reaches the end of the current line, the
-entire word is wrapped to the next line (assuming there is one). When this
-option is off, the word will be split across the line break.
-<DT> O_BLANK
-<DD> Controls field blanking. When this option is on, entering a character at
-the first field position erases the entire field (except for the just-entered
-character).
-<DT> O_AUTOSKIP
-<DD> Controls automatic skip to next field when this one fills. Normally,
-when the forms user tries to type more data into a field than will fit,
-the editing location jumps to next field. When this option is off, the
-user's cursor will hang at the end of the field. This option is ignored
-in dynamic fields that have not reached their size limit.
-<DT> O_NULLOK
-<DD> Controls whether <A HREF="#fvalidation">validation</A> is applied to
-blank fields. Normally, it is not; the user can leave a field blank
-without invoking the usual validation check on exit. If this option is
-off on a field, exit from it will invoke a validation check.
-<DT> O_PASSOK
-<DD> Controls whether validation occurs on every exit, or only after
-the field is modified. Normally the latter is true. Setting O_PASSOK
-may be useful if your field's validation function may change during
-forms processing.
-<DT> O_STATIC
-<DD> Controls whether the field is fixed to its initial dimensions. If you
-turn this off, the field becomes <A HREF="#fdynamic">dynamic</A> and will
-stretch to fit entered data.
-</DL>
-
-A field's options cannot be changed while the field is currently selected.
-However, options may be changed on posted fields that are not current. <P>
-
-The option values are bit-masks and can be composed with logical-or in
-the obvious way.
-
-<H2><A NAME="fstatus">Field Status</A></H2>
-
-Every field has a status flag, which is set to FALSE when the field is
-created and TRUE when the value in field buffer 0 changes. This flag can
-be queried and set directly:
-
-<PRE>
-int set_field_status(FIELD *field, /* field to alter */
- int status); /* mode to set */
-
-int field_status(FIELD *field); /* fetch mode of field */
-</PRE>
-
-Setting this flag under program control can be useful if you use the same
-form repeatedly, looking for modified fields each time. <P>
-
-Calling <CODE>field_status()</CODE> on a field not currently selected
-for input will return a correct value. Calling <CODE>field_status()</CODE> on a
-field that is currently selected for input may not necessarily give a
-correct field status value, because entered data isn't necessarily copied to
-buffer zero before the exit validation check.
-
-To guarantee that the returned status value reflects reality, call
-<CODE>field_status()</CODE> either (1) in the field's exit validation check
-routine, (2) from the field's or form's initialization or termination
-hooks, or (3) just after a <CODE>REQ_VALIDATION</CODE> request has been
-processed by the forms driver.
-
-<H2><A NAME="fuser">Field User Pointer</A></H2>
-
-Each field structure contains one character pointer slot that is not used
-by the forms library. It is intended to be used by applications to store
-private per-field data. You can manipulate it with:
-
-<PRE>
-int set_field_userptr(FIELD *field, /* field to alter */
- char *userptr); /* mode to set */
-
-char *field_userptr(FIELD *field); /* fetch mode of field */
-</PRE>
-
-(Properly, this user pointer field ought to have <CODE>(void *)</CODE> type.
-The <CODE>(char *)</CODE> type is retained for System V compatibility.) <P>
-
-It is valid to set the user pointer of the default field (with a
-<CODE>set_field_userptr()</CODE> call passed a NULL field pointer.)
-When a new field is created, the default-field user pointer is copied
-to initialize the new field's user pointer.
-
-<H2><A NAME="fdynamic">Variable-Sized Fields</A></H2>
-
-Normally, a field is fixed at the size specified for it at creation
-time. If, however, you turn off its O_STATIC bit, it becomes
-<DFN>dynamic</DFN> and will automatically resize itself to accommodate
-data as it is entered. If the field has extra buffers associated with it,
-they will grow right along with the main input buffer. <P>
-
-A one-line dynamic field will have a fixed height (1) but variable
-width, scrolling horizontally to display data within the field area as
-originally dimensioned and located. A multi-line dynamic field will
-have a fixed width, but variable height (number of rows), scrolling
-vertically to display data within the field area as originally
-dimensioned and located. <P>
-
-Normally, a dynamic field is allowed to grow without limit. But it is
-possible to set an upper limit on the size of a dynamic field. You do
-it with this function:
-
-<PRE>
-int set_max_field(FIELD *field, /* field to alter (may not be NULL) */
- int max_size); /* upper limit on field size */
-</PRE>
-
-If the field is one-line, <CODE>max_size</CODE> is taken to be a column size
-limit; if it is multi-line, it is taken to be a line size limit. To disable
-any limit, use an argument of zero. The growth limit can be changed whether
-or not the O_STATIC bit is on, but has no effect until it is. <P>
-
-The following properties of a field change when it becomes dynamic:
-
-<UL>
-<LI>If there is no growth limit, there is no final position of the field;
-therefore <CODE>O_AUTOSKIP</CODE> and <CODE>O_NL_OVERLOAD</CODE> are ignored.
-<LI>Field justification will be ignored (though whatever justification is
-set up will be retained internally and can be queried).
-<LI>The <CODE>dup_field()</CODE> and <CODE>link_field()</CODE> calls copy
-dynamic-buffer sizes. If the <CODE>O_STATIC</CODE> option is set on one of a
-collection of links, buffer resizing will occur only when the field is
-edited through that link.
-<LI>The call <CODE>field_info()</CODE> will retrieve the original static size of
-the field; use <CODE>dynamic_field_info()</CODE> to get the actual dynamic size.
-</UL>
-
-<H2><A NAME="fvalidation">Field Validation</A></H2>
-
-By default, a field will accept any data that will fit in its input buffer.
-However, it is possible to attach a validation type to a field. If you do
-this, any attempt to leave the field while it contains data that doesn't
-match the validation type will fail. Some validation types also have a
-character-validity check for each time a character is entered in the field. <P>
-
-A field's validation check (if any) is not called when
-<CODE>set_field_buffer()</CODE> modifies the input buffer, nor when that buffer
-is changed through a linked field. <P>
-
-The <CODE>form</CODE> library provides a rich set of pre-defined validation
-types, and gives you the capability to define custom ones of your own. You
-can examine and change field validation attributes with the following
-functions:
-
-<PRE>
-int set_field_type(FIELD *field, /* field to alter */
- FIELDTYPE *ftype, /* type to associate */
- ...); /* additional arguments*/
-
-FIELDTYPE *field_type(FIELD *field); /* field to query */
-</PRE>
-
-The validation type of a field is considered an attribute of the field. As
-with other field attributes, Also, doing <CODE>set_field_type()</CODE> with a
-<CODE>NULL</CODE> field default will change the system default for validation of
-newly-created fields. <P>
-
-Here are the pre-defined validation types:
-
-<H3><A NAME="ftype_alpha">TYPE_ALPHA</A></H3>
-
-This field type accepts alphabetic data; no blanks, no digits, no special
-characters (this is checked at character-entry time). It is set up with:
-
-<PRE>
-int set_field_type(FIELD *field, /* field to alter */
- TYPE_ALPHA, /* type to associate */
- int width); /* maximum width of field */
-</PRE>
-
-The <CODE>width</CODE> argument sets a minimum width of data. Typically
-you'll want to set this to the field width; if it's greater than the
-field width, the validation check will always fail. A minimum width
-of zero makes field completion optional.
-
-<H3><A NAME="ftype_alnum">TYPE_ALNUM</A></H3>
-
-This field type accepts alphabetic data and digits; no blanks, no special
-characters (this is checked at character-entry time). It is set up with:
-
-<PRE>
-int set_field_type(FIELD *field, /* field to alter */
- TYPE_ALNUM, /* type to associate */
- int width); /* maximum width of field */
-</PRE>
-
-The <CODE>width</CODE> argument sets a minimum width of data. As with
-TYPE_ALPHA, typically you'll want to set this to the field width; if it's
-greater than the field width, the validation check will always fail. A
-minimum width of zero makes field completion optional.
-
-<H3><A NAME="ftype_enum">TYPE_ENUM</A></H3>
-
-This type allows you to restrict a field's values to be among a specified
-set of string values (for example, the two-letter postal codes for U.S.
-states). It is set up with:
-
-<PRE>
-int set_field_type(FIELD *field, /* field to alter */
- TYPE_ENUM, /* type to associate */
- char **valuelist; /* list of possible values */
- int checkcase; /* case-sensitive? */
- int checkunique); /* must specify uniquely? */
-</PRE>
-
-The <CODE>valuelist</CODE> parameter must point at a NULL-terminated list of
-valid strings. The <CODE>checkcase</CODE> argument, if true, makes comparison
-with the string case-sensitive. <P>
-
-When the user exits a TYPE_ENUM field, the validation procedure tries to
-complete the data in the buffer to a valid entry. If a complete choice string
-has been entered, it is of course valid. But it is also possible to enter a
-prefix of a valid string and have it completed for you. <P>
-
-By default, if you enter such a prefix and it matches more than one value
-in the string list, the prefix will be completed to the first matching
-value. But the <CODE>checkunique</CODE> argument, if true, requires prefix
-matches to be unique in order to be valid. <P>
-
-The <CODE>REQ_NEXT_CHOICE</CODE> and <CODE>REQ_PREV_CHOICE</CODE> input requests
-can be particularly useful with these fields.
-
-<H3><A NAME="ftype_integer">TYPE_INTEGER</A></H3>
-
-This field type accepts an integer. It is set up as follows:
-
-<PRE>
-int set_field_type(FIELD *field, /* field to alter */
- TYPE_INTEGER, /* type to associate */
- int padding, /* # places to zero-pad to */
- int vmin, int vmax); /* valid range */
-</PRE>
-
-Valid characters consist of an optional leading minus and digits.
-The range check is performed on exit. If the range maximum is less
-than or equal to the minimum, the range is ignored. <P>
-
-If the value passes its range check, it is padded with as many leading
-zero digits as necessary to meet the padding argument. <P>
-
-A <CODE>TYPE_INTEGER</CODE> value buffer can conveniently be interpreted
-with the C library function <CODE>atoi(3)</CODE>.
-
-<H3><A NAME="ftype_numeric">TYPE_NUMERIC</A></H3>
-
-This field type accepts a decimal number. It is set up as follows:
-
-<PRE>
-int set_field_type(FIELD *field, /* field to alter */
- TYPE_NUMERIC, /* type to associate */
- int padding, /* # places of precision */
- double vmin, double vmax); /* valid range */
-</PRE>
-
-Valid characters consist of an optional leading minus and digits. possibly
-including a decimal point. If your system supports locale's, the decimal point
-character used must be the one defined by your locale. The range check is
-performed on exit. If the range maximum is less than or equal to the minimum,
-the range is ignored. <P>
-
-If the value passes its range check, it is padded with as many trailing
-zero digits as necessary to meet the padding argument. <P>
-
-A <CODE>TYPE_NUMERIC</CODE> value buffer can conveniently be interpreted
-with the C library function <CODE>atof(3)</CODE>.
-
-<H3><A NAME="ftype_regexp">TYPE_REGEXP</A></H3>
-
-This field type accepts data matching a regular expression. It is set up
-as follows:
-
-<PRE>
-int set_field_type(FIELD *field, /* field to alter */
- TYPE_REGEXP, /* type to associate */
- char *regexp); /* expression to match */
-</PRE>
-
-The syntax for regular expressions is that of <CODE>regcomp(3)</CODE>.
-The check for regular-expression match is performed on exit.
-
-<H2><A NAME="fbuffer">Direct Field Buffer Manipulation</A></H2>
-
-The chief attribute of a field is its buffer contents. When a form has
-been completed, your application usually needs to know the state of each
-field buffer. You can find this out with:
-
-<PRE>
-char *field_buffer(FIELD *field, /* field to query */
- int bufindex); /* number of buffer to query */
-</PRE>
-
-Normally, the state of the zero-numbered buffer for each field is set by
-the user's editing actions on that field. It's sometimes useful to be able
-to set the value of the zero-numbered (or some other) buffer from your
-application:
-
-<PRE>
-int set_field_buffer(FIELD *field, /* field to alter */
- int bufindex, /* number of buffer to alter */
- char *value); /* string value to set */
-</PRE>
-
-If the field is not large enough and cannot be resized to a sufficiently
-large size to contain the specified value, the value will be truncated
-to fit. <P>
-
-Calling <CODE>field_buffer()</CODE> with a null field pointer will raise an
-error. Calling <CODE>field_buffer()</CODE> on a field not currently selected
-for input will return a correct value. Calling <CODE>field_buffer()</CODE> on a
-field that is currently selected for input may not necessarily give a
-correct field buffer value, because entered data isn't necessarily copied to
-buffer zero before the exit validation check.
-
-To guarantee that the returned buffer value reflects on-screen reality,
-call <CODE>field_buffer()</CODE> either (1) in the field's exit validation
-check routine, (2) from the field's or form's initialization or termination
-hooks, or (3) just after a <CODE>REQ_VALIDATION</CODE> request has been processed
-by the forms driver.
-
-<H2><A NAME="formattrs">Attributes of Forms</A></H2>
-
-As with field attributes, form attributes inherit a default from a
-system default form structure. These defaults can be queried or set by
-of these functions using a form-pointer argument of <CODE>NULL</CODE>. <P>
-
-The principal attribute of a form is its field list. You can query
-and change this list with:
-
-<PRE>
-int set_form_fields(FORM *form, /* form to alter */
- FIELD **fields); /* fields to connect */
-
-char *form_fields(FORM *form); /* fetch fields of form */
-
-int field_count(FORM *form); /* count connect fields */
-</PRE>
-
-The second argument of <CODE>set_form_fields()</CODE> may be a
-NULL-terminated field pointer array like the one required by
-<CODE>new_form()</CODE>. In that case, the old fields of the form are
-disconnected but not freed (and eligible to be connected to other
-forms), then the new fields are connected. <P>
-
-It may also be null, in which case the old fields are disconnected
-(and not freed) but no new ones are connected. <P>
-
-The <CODE>field_count()</CODE> function simply counts the number of fields
-connected to a given from. It returns -1 if the form-pointer argument
-is NULL.
-
-<H2><A NAME="fdisplay">Control of Form Display</A></H2>
-
-In the overview section, you saw that to display a form you normally
-start by defining its size (and fields), posting it, and refreshing
-the screen. There is an hidden step before posting, which is the
-association of the form with a frame window (actually, a pair of
-windows) within which it will be displayed. By default, the forms
-library associates every form with the full-screen window
-<CODE>stdscr</CODE>. <P>
-
-By making this step explicit, you can associate a form with a declared
-frame window on your screen display. This can be useful if you want to
-adapt the form display to different screen sizes, dynamically tile
-forms on the screen, or use a form as part of an interface layout
-managed by <A HREF="#panels">panels</A>. <P>
-
-The two windows associated with each form have the same functions as
-their analogues in the <A HREF="#menu">menu library</A>. Both these
-windows are painted when the form is posted and erased when the form
-is unposted. <P>
-
-The outer or frame window is not otherwise touched by the form
-routines. It exists so the programmer can associate a title, a
-border, or perhaps help text with the form and have it properly
-refreshed or erased at post/unpost time. The inner window or subwindow
-is where the current form page is actually displayed. <P>
-
-In order to declare your own frame window for a form, you'll need to
-know the size of the form's bounding rectangle. You can get this
-information with:
-
-<PRE>
-int scale_form(FORM *form, /* form to query */
- int *rows, /* form rows */
- int *cols); /* form cols */
-</PRE>
-
-The form dimensions are passed back in the locations pointed to by
-the arguments. Once you have this information, you can use it to
-declare of windows, then use one of these functions:
-
-<PRE>
-int set_form_win(FORM *form, /* form to alter */
- WINDOW *win); /* frame window to connect */
-
-WINDOW *form_win(FORM *form); /* fetch frame window of form */
-
-int set_form_sub(FORM *form, /* form to alter */
- WINDOW *win); /* form subwindow to connect */
-
-WINDOW *form_sub(FORM *form); /* fetch form subwindow of form */
-</PRE>
-
-Note that curses operations, including <CODE>refresh()</CODE>, on the form,
-should be done on the frame window, not the form subwindow. <P>
-
-It is possible to check from your application whether all of a
-scrollable field is actually displayed within the menu subwindow. Use
-these functions:
-
-<PRE>
-int data_ahead(FORM *form); /* form to be queried */
-
-int data_behind(FORM *form); /* form to be queried */
-</PRE>
-
-The function <CODE>data_ahead()</CODE> returns TRUE if (a) the current
-field is one-line and has undisplayed data off to the right, (b) the current
-field is multi-line and there is data off-screen below it. <P>
-
-The function <CODE>data_behind()</CODE> returns TRUE if the first (upper
-left hand) character position is off-screen (not being displayed). <P>
-
-Finally, there is a function to restore the form window's cursor to the
-value expected by the forms driver:
-
-<PRE>
-int pos_form_cursor(FORM *) /* form to be queried */
-</PRE>
-
-If your application changes the form window cursor, call this function before
-handing control back to the forms driver in order to re-synchronize it.
-
-<H2><A NAME="fdriver">Input Processing in the Forms Driver</A></H2>
-
-The function <CODE>form_driver()</CODE> handles virtualized input requests
-for form navigation, editing, and validation requests, just as
-<CODE>menu_driver</CODE> does for menus (see the section on <A
-HREF="#minput">menu input handling</A>).
-
-<PRE>
-int form_driver(FORM *form, /* form to pass input to */
- int request); /* form request code */
-</PRE>
-
-Your input virtualization function needs to take input and then convert it
-to either an alphanumeric character (which is treated as data to be
-entered in the currently-selected field), or a forms processing request. <P>
-
-The forms driver provides hooks (through input-validation and
-field-termination functions) with which your application code can check
-that the input taken by the driver matched what was expected.
-
-<H3><A NAME="fpage">Page Navigation Requests</A></H3>
-
-These requests cause page-level moves through the form,
-triggering display of a new form screen.
-
-<DL>
-<DT> <CODE>REQ_NEXT_PAGE</CODE>
-<DD> Move to the next form page.
-<DT> <CODE>REQ_PREV_PAGE</CODE>
-<DD> Move to the previous form page.
-<DT> <CODE>REQ_FIRST_PAGE</CODE>
-<DD> Move to the first form page.
-<DT> <CODE>REQ_LAST_PAGE</CODE>
-<DD> Move to the last form page.
-</DL>
-
-These requests treat the list as cyclic; that is, <CODE>REQ_NEXT_PAGE</CODE>
-from the last page goes to the first, and <CODE>REQ_PREV_PAGE</CODE> from
-the first page goes to the last.
-
-<H3><A NAME="ffield">Inter-Field Navigation Requests</A></H3>
-
-These requests handle navigation between fields on the same page.
-
-<DL>
-<DT> <CODE>REQ_NEXT_FIELD</CODE>
-<DD> Move to next field.
-<DT> <CODE>REQ_PREV_FIELD</CODE>
-<DD> Move to previous field.
-<DT> <CODE>REQ_FIRST_FIELD</CODE>
-<DD> Move to the first field.
-<DT> <CODE>REQ_LAST_FIELD</CODE>
-<DD> Move to the last field.
-<DT> <CODE>REQ_SNEXT_FIELD</CODE>
-<DD> Move to sorted next field.
-<DT> <CODE>REQ_SPREV_FIELD</CODE>
-<DD> Move to sorted previous field.
-<DT> <CODE>REQ_SFIRST_FIELD</CODE>
-<DD> Move to the sorted first field.
-<DT> <CODE>REQ_SLAST_FIELD</CODE>
-<DD> Move to the sorted last field.
-<DT> <CODE>REQ_LEFT_FIELD</CODE>
-<DD> Move left to field.
-<DT> <CODE>REQ_RIGHT_FIELD</CODE>
-<DD> Move right to field.
-<DT> <CODE>REQ_UP_FIELD</CODE>
-<DD> Move up to field.
-<DT> <CODE>REQ_DOWN_FIELD</CODE>
-<DD> Move down to field.
-</DL>
-
-These requests treat the list of fields on a page as cyclic; that is,
-<CODE>REQ_NEXT_FIELD</CODE> from the last field goes to the first, and
-<CODE>REQ_PREV_FIELD</CODE> from the first field goes to the last. The
-order of the fields for these (and the <CODE>REQ_FIRST_FIELD</CODE> and
-<CODE>REQ_LAST_FIELD</CODE> requests) is simply the order of the field
-pointers in the form array (as set up by <CODE>new_form()</CODE> or
-<CODE>set_form_fields()</CODE> <P>
-
-It is also possible to traverse the fields as if they had been sorted in
-screen-position order, so the sequence goes left-to-right and top-to-bottom.
-To do this, use the second group of four sorted-movement requests. <P>
-
-Finally, it is possible to move between fields using visual directions up,
-down, right, and left. To accomplish this, use the third group of four
-requests. Note, however, that the position of a form for purposes of these
-requests is its upper-left corner. <P>
-
-For example, suppose you have a multi-line field B, and two
-single-line fields A and C on the same line with B, with A to the left
-of B and C to the right of B. A <CODE>REQ_MOVE_RIGHT</CODE> from A will
-go to B only if A, B, and C <EM>all</EM> share the same first line;
-otherwise it will skip over B to C.
-
-<H3><A NAME="fifield">Intra-Field Navigation Requests</A></H3>
-
-These requests drive movement of the edit cursor within the currently
-selected field.
-
-<DL>
-<DT> <CODE>REQ_NEXT_CHAR</CODE>
-<DD> Move to next character.
-<DT> <CODE>REQ_PREV_CHAR</CODE>
-<DD> Move to previous character.
-<DT> <CODE>REQ_NEXT_LINE</CODE>
-<DD> Move to next line.
-<DT> <CODE>REQ_PREV_LINE</CODE>
-<DD> Move to previous line.
-<DT> <CODE>REQ_NEXT_WORD</CODE>
-<DD> Move to next word.
-<DT> <CODE>REQ_PREV_WORD</CODE>
-<DD> Move to previous word.
-<DT> <CODE>REQ_BEG_FIELD</CODE>
-<DD> Move to beginning of field.
-<DT> <CODE>REQ_END_FIELD</CODE>
-<DD> Move to end of field.
-<DT> <CODE>REQ_BEG_LINE</CODE>
-<DD> Move to beginning of line.
-<DT> <CODE>REQ_END_LINE</CODE>
-<DD> Move to end of line.
-<DT> <CODE>REQ_LEFT_CHAR</CODE>
-<DD> Move left in field.
-<DT> <CODE>REQ_RIGHT_CHAR</CODE>
-<DD> Move right in field.
-<DT> <CODE>REQ_UP_CHAR</CODE>
-<DD> Move up in field.
-<DT> <CODE>REQ_DOWN_CHAR</CODE>
-<DD> Move down in field.
-</DL>
-
-Each <EM>word</EM> is separated from the previous and next characters
-by whitespace. The commands to move to beginning and end of line or field
-look for the first or last non-pad character in their ranges.
-
-<H3><A NAME="fscroll">Scrolling Requests</A></H3>
-
-Fields that are dynamic and have grown and fields explicitly created
-with offscreen rows are scrollable. One-line fields scroll horizontally;
-multi-line fields scroll vertically. Most scrolling is triggered by
-editing and intra-field movement (the library scrolls the field to keep the
-cursor visible). It is possible to explicitly request scrolling with the
-following requests:
-
-<DL>
-<DT> <CODE>REQ_SCR_FLINE</CODE>
-<DD> Scroll vertically forward a line.
-<DT> <CODE>REQ_SCR_BLINE</CODE>
-<DD> Scroll vertically backward a line.
-<DT> <CODE>REQ_SCR_FPAGE</CODE>
-<DD> Scroll vertically forward a page.
-<DT> <CODE>REQ_SCR_BPAGE</CODE>
-<DD> Scroll vertically backward a page.
-<DT> <CODE>REQ_SCR_FHPAGE</CODE>
-<DD> Scroll vertically forward half a page.
-<DT> <CODE>REQ_SCR_BHPAGE</CODE>
-<DD> Scroll vertically backward half a page.
-<DT> <CODE>REQ_SCR_FCHAR</CODE>
-<DD> Scroll horizontally forward a character.
-<DT> <CODE>REQ_SCR_BCHAR</CODE>
-<DD> Scroll horizontally backward a character.
-<DT> <CODE>REQ_SCR_HFLINE</CODE>
-<DD> Scroll horizontally one field width forward.
-<DT> <CODE>REQ_SCR_HBLINE</CODE>
-<DD> Scroll horizontally one field width backward.
-<DT> <CODE>REQ_SCR_HFHALF</CODE>
-<DD> Scroll horizontally one half field width forward.
-<DT> <CODE>REQ_SCR_HBHALF</CODE>
-<DD> Scroll horizontally one half field width backward.
-</DL>
-
-For scrolling purposes, a <EM>page</EM> of a field is the height
-of its visible part.
-
-<H3><A NAME="fedit">Editing Requests</A></H3>
-
-When you pass the forms driver an ASCII character, it is treated as a
-request to add the character to the field's data buffer. Whether this
-is an insertion or a replacement depends on the field's edit mode
-(insertion is the default. <P>
-
-The following requests support editing the field and changing the edit
-mode:
-
-<DL>
-<DT> <CODE>REQ_INS_MODE</CODE>
-<DD> Set insertion mode.
-<DT> <CODE>REQ_OVL_MODE</CODE>
-<DD> Set overlay mode.
-<DT> <CODE>REQ_NEW_LINE</CODE>
-<DD> New line request (see below for explanation).
-<DT> <CODE>REQ_INS_CHAR</CODE>
-<DD> Insert space at character location.
-<DT> <CODE>REQ_INS_LINE</CODE>
-<DD> Insert blank line at character location.
-<DT> <CODE>REQ_DEL_CHAR</CODE>
-<DD> Delete character at cursor.
-<DT> <CODE>REQ_DEL_PREV</CODE>
-<DD> Delete previous word at cursor.
-<DT> <CODE>REQ_DEL_LINE</CODE>
-<DD> Delete line at cursor.
-<DT> <CODE>REQ_DEL_WORD</CODE>
-<DD> Delete word at cursor.
-<DT> <CODE>REQ_CLR_EOL</CODE>
-<DD> Clear to end of line.
-<DT> <CODE>REQ_CLR_EOF</CODE>
-<DD> Clear to end of field.
-<DT> <CODE>REQ_CLEAR_FIELD</CODE>
-<DD> Clear entire field.
-</DL>
-
-The behavior of the <CODE>REQ_NEW_LINE</CODE> and <CODE>REQ_DEL_PREV</CODE> requests
-is complicated and partly controlled by a pair of forms options.
-The special cases are triggered when the cursor is at the beginning of
-a field, or on the last line of the field. <P>
-
-First, we consider <CODE>REQ_NEW_LINE</CODE>: <P>
-
-The normal behavior of <CODE>REQ_NEW_LINE</CODE> in insert mode is to break the
-current line at the position of the edit cursor, inserting the portion of
-the current line after the cursor as a new line following the current
-and moving the cursor to the beginning of that new line (you may think
-of this as inserting a newline in the field buffer). <P>
-
-The normal behavior of <CODE>REQ_NEW_LINE</CODE> in overlay mode is to clear the
-current line from the position of the edit cursor to end of line.
-The cursor is then moved to the beginning of the next line. <P>
-
-However, <CODE>REQ_NEW_LINE</CODE> at the beginning of a field, or on the
-last line of a field, instead does a <CODE>REQ_NEXT_FIELD</CODE>.
-<CODE>O_NL_OVERLOAD</CODE> option is off, this special action is
-disabled. <P>
-
-Now, let us consider <CODE>REQ_DEL_PREV</CODE>: <P>
-
-The normal behavior of <CODE>REQ_DEL_PREV</CODE> is to delete the previous
-character. If insert mode is on, and the cursor is at the start of a
-line, and the text on that line will fit on the previous one, it
-instead appends the contents of the current line to the previous one
-and deletes the current line (you may think of this as deleting a
-newline from the field buffer). <P>
-
-However, <CODE>REQ_DEL_PREV</CODE> at the beginning of a field is instead
-treated as a <CODE>REQ_PREV_FIELD</CODE>. <P> If the
-<CODE>O_BS_OVERLOAD</CODE> option is off, this special action is
-disabled and the forms driver just returns <CODE>E_REQUEST_DENIED</CODE>. <P>
-
-See <A HREF="#frmoptions">Form Options</A> for discussion of how to set
-and clear the overload options.
-
-<H3><A NAME="forder">Order Requests</A></H3>
-
-If the type of your field is ordered, and has associated functions
-for getting the next and previous values of the type from a given value,
-there are requests that can fetch that value into the field buffer:
-
-<DL>
-<DT> <CODE>REQ_NEXT_CHOICE</CODE>
-<DD> Place the successor value of the current value in the buffer.
-<DT> <CODE>REQ_PREV_CHOICE</CODE>
-<DD> Place the predecessor value of the current value in the buffer.
-</DL>
-
-Of the built-in field types, only <CODE>TYPE_ENUM</CODE> has built-in successor
-and predecessor functions. When you define a field type of your own
-(see <A HREF="#fcustom">Custom Validation Types</A>), you can associate
-our own ordering functions.
-
-<H3><A NAME="fappcmds">Application Commands</A></H3>
-
-Form requests are represented as integers above the <CODE>curses</CODE> value
-greater than <CODE>KEY_MAX</CODE> and less than or equal to the constant
-<CODE>MAX_COMMAND</CODE>. If your input-virtualization routine returns a
-value above <CODE>MAX_COMMAND</CODE>, the forms driver will ignore it.
-
-<H2><A NAME="fhooks">Field Change Hooks</A></H2>
-
-It is possible to set function hooks to be executed whenever the
-current field or form changes. Here are the functions that support this:
-
-<PRE>
-typedef void (*HOOK)(); /* pointer to function returning void */
-
-int set_form_init(FORM *form, /* form to alter */
- HOOK hook); /* initialization hook */
-
-HOOK form_init(FORM *form); /* form to query */
-
-int set_form_term(FORM *form, /* form to alter */
- HOOK hook); /* termination hook */
-
-HOOK form_term(FORM *form); /* form to query */
-
-int set_field_init(FORM *form, /* form to alter */
- HOOK hook); /* initialization hook */
-
-HOOK field_init(FORM *form); /* form to query */
-
-int set_field_term(FORM *form, /* form to alter */
- HOOK hook); /* termination hook */
-
-HOOK field_term(FORM *form); /* form to query */
-</PRE>
-
-These functions allow you to either set or query four different hooks.
-In each of the set functions, the second argument should be the
-address of a hook function. These functions differ only in the timing
-of the hook call.
-
-<DL>
-<DT> form_init
-<DD> This hook is called when the form is posted; also, just after
-each page change operation.
-<DT> field_init
-<DD> This hook is called when the form is posted; also, just after
-each field change
-<DT> field_term
-<DD> This hook is called just after field validation; that is, just before
-the field is altered. It is also called when the form is unposted.
-<DT> form_term
-<DD> This hook is called when the form is unposted; also, just before
-each page change operation.
-</DL>
-
-Calls to these hooks may be triggered
-<OL>
-<LI>When user editing requests are processed by the forms driver
-<LI>When the current page is changed by <CODE>set_current_field()</CODE> call
-<LI>When the current field is changed by a <CODE>set_form_page()</CODE> call
-</OL>
-
-See <A NAME="ffocus">Field Change Commands</A> for discussion of the latter
-two cases. <P>
-
-You can set a default hook for all fields by passing one of the set functions
-a NULL first argument. <P>
-
-You can disable any of these hooks by (re)setting them to NULL, the default
-value.
-
-<H2><A HREF="#ffocus">Field Change Commands</A></H2>
-
-Normally, navigation through the form will be driven by the user's
-input requests. But sometimes it is useful to be able to move the
-focus for editing and viewing under control of your application, or
-ask which field it currently is in. The following functions help you
-accomplish this:
-
-<PRE>
-int set_current_field(FORM *form, /* form to alter */
- FIELD *field); /* field to shift to */
-
-FIELD *current_field(FORM *form); /* form to query */
-
-int field_index(FORM *form, /* form to query */
- FIELD *field); /* field to get index of */
-</PRE>
-
-The function <CODE>field_index()</CODE> returns the index of the given field
-in the given form's field array (the array passed to <CODE>new_form()</CODE> or
-<CODE>set_form_fields()</CODE>). <P>
-
-The initial current field of a form is the first active field on the
-first page. The function <CODE>set_form_fields()</CODE> resets this.<P>
-
-It is also possible to move around by pages.
-
-<PRE>
-int set_form_page(FORM *form, /* form to alter */
- int page); /* page to go to (0-origin) */
-
-int form_page(FORM *form); /* return form's current page */
-</PRE>
-
-The initial page of a newly-created form is 0. The function
-<CODE>set_form_fields()</CODE> resets this.
-
-<H2><A NAME="frmoptions">Form Options</A></H2>
-
-Like fields, forms may have control option bits. They can be changed
-or queried with these functions:
-
-<PRE>
-int set_form_opts(FORM *form, /* form to alter */
- int attr); /* attribute to set */
-
-int form_opts_on(FORM *form, /* form to alter */
- int attr); /* attributes to turn on */
-
-int form_opts_off(FORM *form, /* form to alter */
- int attr); /* attributes to turn off */
-
-int form_opts(FORM *form); /* form to query */
-</PRE>
-
-By default, all options are on. Here are the available option bits:
-
-<DL>
-<DT> O_NL_OVERLOAD
-<DD> Enable overloading of <CODE>REQ_NEW_LINE</CODE> as described in <A
-href="#fedit">Editing Requests</A>. The value of this option is
-ignored on dynamic fields that have not reached their size limit;
-these have no last line, so the circumstances for triggering a
-<CODE>REQ_NEXT_FIELD</CODE> never arise.
-<DT> O_BS_OVERLOAD
-<DD> Enable overloading of <CODE>REQ_DEL_PREV</CODE> as described in
-<A href="#fedit">Editing Requests</A>.
-</DL>
-
-The option values are bit-masks and can be composed with logical-or in
-the obvious way.
-
-<H2><A NAME="fcustom">Custom Validation Types</A></H2>
-
-The <CODE>form</CODE> library gives you the capability to define custom
-validation types of your own. Further, the optional additional arguments
-of <CODE>set_field_type</CODE> effectively allow you to parameterize validation
-types. Most of the complications in the validation-type interface have to
-do with the handling of the additional arguments within custom validation
-functions.
-
-<H3><A NAME="flinktypes">Union Types</A></H3>
-
-The simplest way to create a custom data type is to compose it from two
-preexisting ones:
-
-<PRE>
-FIELD *link_fieldtype(FIELDTYPE *type1,
- FIELDTYPE *type2);
-</PRE>
-
-This function creates a field type that will accept any of the values
-legal for either of its argument field types (which may be either
-predefined or programmer-defined).
-
-If a <CODE>set_field_type()</CODE> call later requires arguments, the new
-composite type expects all arguments for the first type, than all arguments
-for the second. Order functions (see <A HREF="#forder">Order Requests</A>)
-associated with the component types will work on the composite; what it does
-is check the validation function for the first type, then for the second, to
-figure what type the buffer contents should be treated as.
-
-<H3><A NAME="fnewtypes">New Field Types</A></H3>
-
-To create a field type from scratch, you need to specify one or both of the
-following things:
-
-<UL>
-<LI>A character-validation function, to check each character as it is entered.
-<LI>A field-validation function to be applied on exit from the field.
-</UL>
-
-Here's how you do that:
-<PRE>
-typedef int (*HOOK)(); /* pointer to function returning int */
-
-FIELDTYPE *new_fieldtype(HOOK f_validate, /* field validator */
- HOOK c_validate) /* character validator */
-
-
-int free_fieldtype(FIELDTYPE *ftype); /* type to free */
-</PRE>
-
-At least one of the arguments of <CODE>new_fieldtype()</CODE> must be
-non-NULL. The forms driver will automatically call the new type's
-validation functions at appropriate points in processing a field of
-the new type. <P>
-
-The function <CODE>free_fieldtype()</CODE> deallocates the argument
-fieldtype, freeing all storage associated with it. <P>
-
-Normally, a field validator is called when the user attempts to
-leave the field. Its first argument is a field pointer, from which it
-can get to field buffer 0 and test it. If the function returns TRUE,
-the operation succeeds; if it returns FALSE, the edit cursor stays in
-the field. <P>
-
-A character validator gets the character passed in as a first argument.
-It too should return TRUE if the character is valid, FALSE otherwise.
-
-<H3><A NAME="fcheckargs">Validation Function Arguments</A></H3>
-
-Your field- and character- validation functions will be passed a
-second argument as well. This second argument is the address of a
-structure (which we'll call a <EM>pile</EM>) built from any of the
-field-type-specific arguments passed to <CODE>set_field_type()</CODE>. If
-no such arguments are defined for the field type, this pile pointer
-argument will be NULL. <P>
-
-In order to arrange for such arguments to be passed to your validation
-functions, you must associate a small set of storage-management functions
-with the type. The forms driver will use these to synthesize a pile
-from the trailing arguments of each <CODE>set_field_type()</CODE> argument, and
-a pointer to the pile will be passed to the validation functions. <P>
-
-Here is how you make the association:
-
-<PRE>
-typedef char *(*PTRHOOK)(); /* pointer to function returning (char *) */
-typedef void (*VOIDHOOK)(); /* pointer to function returning void */
-
-int set_fieldtype_arg(FIELDTYPE *type, /* type to alter */
- PTRHOOK make_str, /* make structure from args */
- PTRHOOK copy_str, /* make copy of structure */
- VOIDHOOK free_str); /* free structure storage */
-</PRE>
-
-Here is how the storage-management hooks are used:
-
-<DL>
-<DT> <CODE>make_str</CODE>
-<DD> This function is called by <CODE>set_field_type()</CODE>. It gets one
-argument, a <CODE>va_list</CODE> of the type-specific arguments passed to
-<CODE>set_field_type()</CODE>. It is expected to return a pile pointer to a data
-structure that encapsulates those arguments.
-<DT> <CODE>copy_str</CODE>
-<DD> This function is called by form library functions that allocate new
-field instances. It is expected to take a pile pointer, copy the pile
-to allocated storage, and return the address of the pile copy.
-<DT> <CODE>free_str</CODE>
-<DD> This function is called by field- and type-deallocation routines in the
-library. It takes a pile pointer argument, and is expected to free the
-storage of that pile.
-</DL>
-
-The <CODE>make_str</CODE> and <CODE>copy_str</CODE> functions may return NULL to
-signal allocation failure. The library routines will that call them will
-return error indication when this happens. Thus, your validation functions
-should never see a NULL file pointer and need not check specially for it.
-
-<H3><A NAME="fcustorder">Order Functions For Custom Types</A></H3>
-
-Some custom field types are simply ordered in the same well-defined way
-that <CODE>TYPE_ENUM</CODE> is. For such types, it is possible to define
-successor and predecessor functions to support the <CODE>REQ_NEXT_CHOICE</CODE>
-and <CODE>REQ_PREV_CHOICE</CODE> requests. Here's how:
-
-<PRE>
-typedef int (*INTHOOK)(); /* pointer to function returning int */
-
-int set_fieldtype_arg(FIELDTYPE *type, /* type to alter */
- INTHOOK succ, /* get successor value */
- INTHOOK pred); /* get predecessor value */
-</PRE>
-
-The successor and predecessor arguments will each be passed two arguments;
-a field pointer, and a pile pointer (as for the validation functions). They
-are expected to use the function <CODE>field_buffer()</CODE> to read the
-current value, and <CODE>set_field_buffer()</CODE> on buffer 0 to set the next
-or previous value. Either hook may return TRUE to indicate success (a
-legal next or previous value was set) or FALSE to indicate failure.
-
-<H3><A NAME="fcustprobs">Avoiding Problems</A></H3>
-
-The interface for defining custom types is complicated and tricky.
-Rather than attempting to create a custom type entirely from scratch,
-you should start by studying the library source code for whichever of
-the pre-defined types seems to be closest to what you want. <P>
-
-Use that code as a model, and evolve it towards what you really want.
-You will avoid many problems and annoyances that way. The code
-in the <CODE>ncurses</CODE> library has been specifically exempted from
-the package copyright to support this. <P>
-
-If your custom type defines order functions, have do something intuitive
-with a blank field. A useful convention is to make the successor of a
-blank field the types minimum value, and its predecessor the maximum.
-</BODY>
-</HTML>
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