From d32785554e5217899691b82c33b50ad710f1ce7e Mon Sep 17 00:00:00 2001
From: nicm <nicm@openbsd.org>
Date: Sun, 4 Aug 2024 08:53:43 +0000
Subject: [PATCH] Adjust the logic when deleting last buffer to better preserve
 the selection: if selecting the element below the deleted one fails (because
 as the last one), select the one above it instead. From Daniel Mueller,
 GitHub issue 4043.

---
 usr.bin/tmux/mode-tree.c     |  8 +++++---
 usr.bin/tmux/tmux.h          |  4 ++--
 usr.bin/tmux/window-buffer.c | 15 ++++++++++++---
 3 files changed, 19 insertions(+), 8 deletions(-)

diff --git a/usr.bin/tmux/mode-tree.c b/usr.bin/tmux/mode-tree.c
index 49fe2b7cfdf..8c62602428b 100644
--- a/usr.bin/tmux/mode-tree.c
+++ b/usr.bin/tmux/mode-tree.c
@@ -1,4 +1,4 @@
-/* $OpenBSD: mode-tree.c,v 1.67 2024/05/24 12:39:06 nicm Exp $ */
+/* $OpenBSD: mode-tree.c,v 1.68 2024/08/04 08:53:43 nicm Exp $ */
 
 /*
  * Copyright (c) 2017 Nicholas Marriott <nicholas.marriott@gmail.com>
@@ -261,19 +261,21 @@ mode_tree_up(struct mode_tree_data *mtd, int wrap)
 	}
 }
 
-void
+int
 mode_tree_down(struct mode_tree_data *mtd, int wrap)
 {
 	if (mtd->current == mtd->line_size - 1) {
 		if (wrap) {
 			mtd->current = 0;
 			mtd->offset = 0;
-		}
+		} else
+			return (0);
 	} else {
 		mtd->current++;
 		if (mtd->current > mtd->offset + mtd->height - 1)
 			mtd->offset++;
 	}
+	return (1);
 }
 
 void *
diff --git a/usr.bin/tmux/tmux.h b/usr.bin/tmux/tmux.h
index cc6c014b5a7..a1ffc50b32f 100644
--- a/usr.bin/tmux/tmux.h
+++ b/usr.bin/tmux/tmux.h
@@ -1,4 +1,4 @@
-/* $OpenBSD: tmux.h,v 1.1219 2024/07/12 11:21:18 nicm Exp $ */
+/* $OpenBSD: tmux.h,v 1.1220 2024/08/04 08:53:43 nicm Exp $ */
 
 /*
  * Copyright (c) 2007 Nicholas Marriott <nicholas.marriott@gmail.com>
@@ -3138,7 +3138,7 @@ int	 mode_tree_set_current(struct mode_tree_data *, uint64_t);
 void	 mode_tree_each_tagged(struct mode_tree_data *, mode_tree_each_cb,
 	     struct client *, key_code, int);
 void	 mode_tree_up(struct mode_tree_data *, int);
-void	 mode_tree_down(struct mode_tree_data *, int);
+int	 mode_tree_down(struct mode_tree_data *, int);
 struct mode_tree_data *mode_tree_start(struct window_pane *, struct args *,
 	     mode_tree_build_cb, mode_tree_draw_cb, mode_tree_search_cb,
 	     mode_tree_menu_cb, mode_tree_height_cb, mode_tree_key_cb, void *,
diff --git a/usr.bin/tmux/window-buffer.c b/usr.bin/tmux/window-buffer.c
index 28dcef5ec84..185faf9ebc8 100644
--- a/usr.bin/tmux/window-buffer.c
+++ b/usr.bin/tmux/window-buffer.c
@@ -1,4 +1,4 @@
-/* $OpenBSD: window-buffer.c,v 1.39 2024/08/04 08:39:38 nicm Exp $ */
+/* $OpenBSD: window-buffer.c,v 1.40 2024/08/04 08:53:43 nicm Exp $ */
 
 /*
  * Copyright (c) 2017 Nicholas Marriott <nicholas.marriott@gmail.com>
@@ -408,8 +408,17 @@ window_buffer_do_delete(void *modedata, void *itemdata,
 	struct window_buffer_itemdata	*item = itemdata;
 	struct paste_buffer		*pb;
 
-	if (item == mode_tree_get_current(data->data))
-		mode_tree_down(data->data, 0);
+	if (item == mode_tree_get_current(data->data) &&
+	    !mode_tree_down(data->data, 0)) {
+		/*
+		 *If we were unable to select the item further down we are at
+		 * the end of the list. Move one element up instead, to make
+		 * sure that we preserve a valid selection or we risk having
+		 * the tree build logic reset it to the first item.
+		 */
+		mode_tree_up(data->data, 0);
+	}
+
 	if ((pb = paste_get_name(item->name)) != NULL)
 		paste_free(pb);
 }
-- 
2.20.1