From f2268041490fefabc1f8930c2c8492d4fc37444f Mon Sep 17 00:00:00 2001
From: nicm <nicm>
Date: Tue, 6 Jan 2026 20:05:57 +0000
Subject: [PATCH] Do not send theme unless it has changed, and do not send
 immediately when updates are enabled. GitHub issue 5787.

---
 input-keys.c |  6 ------
 input.c      | 15 ++++++++++++---
 tmux.h       | 21 +++++++++++----------
 window.c     | 18 +++++++++++++-----
 4 files changed, 36 insertions(+), 24 deletions(-)

diff --git a/input-keys.c b/input-keys.c
index 7d7263fb..6a872731 100644
--- a/input-keys.c
+++ b/input-keys.c
@@ -314,12 +314,6 @@ static struct input_key_entry input_key_defaults[] = {
 	{ .key = KEYC_DC|KEYC_BUILD_MODIFIERS,
 	  .data = "\033[3;_~"
 	},
-	{ .key = KEYC_REPORT_DARK_THEME,
-	  .data = "\033[?997;1n"
-	},
-	{ .key = KEYC_REPORT_LIGHT_THEME,
-	  .data = "\033[?997;2n"
-	},
 };
 static const key_code input_key_modifiers[] = {
 	0,
diff --git a/input.c b/input.c
index 4f5bd38f..43d5e9a7 100644
--- a/input.c
+++ b/input.c
@@ -1898,6 +1898,8 @@ input_csi_dispatch_rm_private(struct input_ctx *ictx)
 			break;
 		case 2031:
 			screen_write_mode_clear(sctx, MODE_THEME_UPDATES);
+			if (ictx->wp != NULL)
+				ictx->wp->flags &= ~PANE_THEMECHANGED;
 			break;
 		case 2026:	/* synchronized output */
 			screen_write_stop_sync(ictx->wp);
@@ -2001,6 +2003,10 @@ input_csi_dispatch_sm_private(struct input_ctx *ictx)
 			break;
 		case 2031:
 			screen_write_mode_set(sctx, MODE_THEME_UPDATES);
+			if (ictx->wp != NULL) {
+				ictx->wp->last_theme = window_pane_get_theme(ictx->wp);
+				ictx->wp->flags &= ~PANE_THEMECHANGED;
+			}
 			break;
 		case 2026:	/* synchronized output */
 			screen_write_start_sync(ictx->wp);
@@ -3397,9 +3403,11 @@ input_report_current_theme(struct input_ctx *ictx)
 {
 	struct window_pane	*wp = ictx->wp;
 
-	if (wp == NULL)
-		return;
-	switch (window_pane_get_theme(wp)) {
+	if (wp != NULL) {
+		wp->last_theme = window_pane_get_theme(wp);
+		wp->flags &= ~PANE_THEMECHANGED;
+
+		switch (wp->last_theme) {
 		case THEME_DARK:
 			log_debug("%s: %%%u dark theme", __func__, wp->id);
 			input_reply(ictx, 0, "\033[?997;1n");
@@ -3411,5 +3419,6 @@ input_report_current_theme(struct input_ctx *ictx)
 		case THEME_UNKNOWN:
 			log_debug("%s: %%%u unknown theme", __func__, wp->id);
 			break;
+		}
 	}
 }
diff --git a/tmux.h b/tmux.h
index c738fb67..de7421f5 100644
--- a/tmux.h
+++ b/tmux.h
@@ -1135,6 +1135,16 @@ struct window_pane_resize {
 };
 TAILQ_HEAD(window_pane_resizes, window_pane_resize);
 
+/*
+ * Client theme, this is worked out from the background colour if not reported
+ * by terminal.
+ */
+enum client_theme {
+	THEME_UNKNOWN,
+	THEME_LIGHT,
+	THEME_DARK
+};
+
 /* Child window structure. */
 struct window_pane {
 	u_int		 id;
@@ -1198,6 +1208,7 @@ struct window_pane {
 	struct grid_cell cached_gc;
 	struct grid_cell cached_active_gc;
 	struct colour_palette palette;
+	enum client_theme last_theme;
 
 	int		 pipe_fd;
 	struct bufferevent *pipe_event;
@@ -1876,16 +1887,6 @@ struct overlay_ranges {
 	u_int	nx[OVERLAY_MAX_RANGES];
 };
 
-/*
- * Client theme, this is worked out from the background colour if not reported
- * by terminal.
- */
-enum client_theme {
-	THEME_UNKNOWN,
-	THEME_LIGHT,
-	THEME_DARK
-};
-
 /* Client connection. */
 typedef int (*prompt_input_cb)(struct client *, void *, const char *, int);
 typedef void (*prompt_free_cb)(void *);
diff --git a/window.c b/window.c
index f3b8b8a8..9581c64f 100644
--- a/window.c
+++ b/window.c
@@ -926,7 +926,7 @@ window_pane_create(struct window *w, u_int sx, u_int sy, u_int hlimit)
 	wp = xcalloc(1, sizeof *wp);
 	wp->window = w;
 	wp->options = options_create(w->options);
-	wp->flags = (PANE_STYLECHANGED|PANE_THEMECHANGED);
+	wp->flags = PANE_STYLECHANGED;
 
 	wp->id = next_window_pane_id++;
 	RB_INSERT(window_pane_tree, &all_window_panes, wp);
@@ -1926,24 +1926,32 @@ window_pane_get_theme(struct window_pane *wp)
 void
 window_pane_send_theme_update(struct window_pane *wp)
 {
+	enum client_theme	theme;
+
 	if (wp == NULL || window_pane_exited(wp))
 		return;
 	if (~wp->flags & PANE_THEMECHANGED)
 		return;
 	if (~wp->screen->mode & MODE_THEME_UPDATES)
 		return;
-	switch (window_pane_get_theme(wp)) {
+
+	theme = window_pane_get_theme(wp);
+	if (theme == wp->last_theme)
+		return;
+	wp->last_theme = theme;
+	wp->flags &= ~PANE_THEMECHANGED;
+
+	switch (theme) {
 	case THEME_LIGHT:
 		log_debug("%s: %%%u light theme", __func__, wp->id);
-		input_key_pane(wp, KEYC_REPORT_LIGHT_THEME, NULL);
+		bufferevent_write(wp->event, "\033[?997;2n", 9);
 		break;
 	case THEME_DARK:
 		log_debug("%s: %%%u dark theme", __func__, wp->id);
-		input_key_pane(wp, KEYC_REPORT_DARK_THEME, NULL);
+		bufferevent_write(wp->event, "\033[?997;1n", 9);
 		break;
 	case THEME_UNKNOWN:
 		log_debug("%s: %%%u unknown theme", __func__, wp->id);
 		break;
 	}
-	wp->flags &= ~PANE_THEMECHANGED;
 }