Add basic support for zero width joiners, GitHub issues 1605 and 2784.

diff --git a/usr.bin/tmux/screen-write.c b/usr.bin/tmux/screen-write.c
index 254b54b..42a8ba6 100644 (file)
--- a/usr.bin/tmux/screen-write.c
+++ b/usr.bin/tmux/screen-write.c
@@ -1,4 +1,4 @@
-/* $OpenBSD: screen-write.c,v 1.195 2021/08/06 07:32:21 nicm Exp $ */
+/* $OpenBSD: screen-write.c,v 1.196 2021/08/06 09:34:09 nicm Exp $ */
 
 /*
  * Copyright (c) 2007 Nicholas Marriott <nicholas.marriott@gmail.com>
@@ -1726,6 +1726,8 @@ screen_write_cell(struct screen_write_ctx *ctx, const struct grid_cell *gc)
 {
        struct screen           *s = ctx->s;
        struct grid             *gd = s->grid;
+       const struct utf8_data  *ud = &gc->data;
+       const struct utf8_data   zwj = { "\342\200\215", 0, 3, 0 };
        struct grid_line        *gl;
        struct grid_cell_entry  *gce;
        struct grid_cell         tmp_gc, now_gc;
@@ -1738,16 +1740,38 @@ screen_write_cell(struct screen_write_ctx *ctx, const struct grid_cell *gc)
        if (gc->flags & GRID_FLAG_PADDING)
                return;
 
-       /* If the width is zero, combine onto the previous character. */
-       if (width == 0) {
+       /*
+        * If this is a zero width joiner, set the flag so the next character
+        * will be treated as zero width and appended. Note that we assume a
+        * ZWJ will not change the width - the width of the first character is
+        * used.
+        */
+       if (ud->size == 3 && memcmp(ud->data, "\342\200\215", 3) == 0) {
+               log_debug("zero width joiner at %u,%u", s->cx, s->cy);
+               ctx->flags |= SCREEN_WRITE_ZWJ;
+               return;
+       }
+
+       /*
+        * If the width is zero, combine onto the previous character. We always
+        * combine with the cell to the left of the cursor position. In theory,
+        * the application could have moved the cursor somewhere else, but if
+        * they are silly enough to do that, who cares?
+        */
+       if (ctx->flags & SCREEN_WRITE_ZWJ) {
+               screen_write_collect_flush(ctx, 0, __func__);
+               screen_write_combine(ctx, &zwj, &xx);
+       }
+       if (width == 0 || (ctx->flags & SCREEN_WRITE_ZWJ)) {
+               ctx->flags &= ~SCREEN_WRITE_ZWJ;
                screen_write_collect_flush(ctx, 0, __func__);
-               if ((gc = screen_write_combine(ctx, &gc->data, &xx)) != 0) {
+               if ((gc = screen_write_combine(ctx, ud, &xx)) != 0) {
                        cx = s->cx; cy = s->cy;
                        screen_write_set_cursor(ctx, xx, s->cy);
                        screen_write_initctx(ctx, &ttyctx, 0);
                        ttyctx.cell = gc;
                        tty_write(tty_cmd_cell, &ttyctx);
-                       s->cx = cx; s->cy = cy;
+                       s->cx = xx + gc->data.width; s->cy = cy;
                }
                return;
        }

diff --git a/usr.bin/tmux/tmux.h b/usr.bin/tmux/tmux.h
index 99dbaf4..5b10148 100644 (file)
--- a/usr.bin/tmux/tmux.h
+++ b/usr.bin/tmux/tmux.h
@@ -1,4 +1,4 @@
-/* $OpenBSD: tmux.h,v 1.1112 2021/07/21 08:06:36 nicm Exp $ */
+/* $OpenBSD: tmux.h,v 1.1113 2021/08/06 09:34:09 nicm Exp $ */
 
 /*
  * Copyright (c) 2007 Nicholas Marriott <nicholas.marriott@gmail.com>
@@ -866,6 +866,7 @@ struct screen_write_ctx {
 
        int                              flags;
 #define SCREEN_WRITE_SYNC 0x1
+#define SCREEN_WRITE_ZWJ 0x2
 
        screen_write_init_ctx_cb         init_ctx_cb;
        void                            *arg;