Track window scrolling for damage.

screen-redraw.c

@@ -1,4 +1,4 @@
-/* $OpenBSD: screen-redraw.c,v 1.165 2026/10/14 12:38:18 nicm Exp $ */
+/* $OpenBSD: screen-redraw.c,v 1.166 2026/10/14 12:48:50 nicm Exp $ */
 
 /*
  * Copyright (c) 2026 Nicholas Marriott <nicholas.marriott@gmail.com>
@@ -1111,6 +1111,7 @@ redraw_free_damage(struct window *w)
 		free(rd);
 	}
 	w->damage_count = 0;
+	w->scroll_pending = 0;
 }
 
 /* Collapse all pending damage for a window into one rectangle. */
@@ -1209,6 +1210,39 @@ redraw_damage_window(struct window *w, u_int x, u_int y, u_int sx, u_int sy)
 	redraw_apply_window_damage(w, x, y, sx, sy, 0);
 }
 
+/* Record damage caused by terminal scrolling. */
+void
+redraw_damage_scroll(struct window *w, u_int x, u_int y, u_int sx, u_int sy)
+{
+	if (!w->scroll_pending) {
+		w->scroll_generation++;
+		w->scroll_pending = 1;
+	}
+	redraw_apply_window_damage(w, x, y, sx, sy, REDRAW_DAMAGE_SCROLL);
+}
+
+/* Remember whether this client used terminal scrolling for the damage. */
+void
+redraw_scroll_result(struct tty *tty, const struct tty_ctx *ctx, int failed)
+{
+	struct window_pane	*wp = ctx->arg;
+	struct window		*w;
+
+	if (wp == NULL)
+		return;
+	w = wp->window;
+	if (!w->scroll_pending)
+		return;
+	if (tty->scroll_window != w ||
+	    tty->scroll_generation != w->scroll_generation) {
+		tty->scroll_window = w;
+		tty->scroll_generation = w->scroll_generation;
+		tty->scroll_failed = 0;
+	}
+	if (failed)
+		tty->scroll_failed = 1;
+}
+
 /* Mark all cached redraw scenes as out of date. */
 void
 redraw_invalidate_all_scenes(void)

tmux.h

@@ -1,4 +1,4 @@
-/* $OpenBSD: tmux.h,v 1.1462 2026/10/14 12:33:46 nicm Exp $ */
+/* $OpenBSD: tmux.h,v 1.1463 2026/10/14 12:48:50 nicm Exp $ */
 
 /*
  * Copyright (c) 2007 Nicholas Marriott <nicholas.marriott@gmail.com>
@@ -1464,6 +1464,8 @@ struct window {
 
 	struct redraw_damages	 damage;
 	u_int			 damage_count;
+	uint64_t		 scroll_generation;
+	int			 scroll_pending;
 
 	struct menu_data	*menu;
 	u_int			 menu_last_px;
@@ -1835,6 +1837,10 @@ struct tty {
 
 	struct event	 key_timer;
 	struct tty_key	*key_tree;
+
+	struct window	*scroll_window;
+	uint64_t	 scroll_generation;
+	int		 scroll_failed;
 };
 
 /* Terminal command context. */
@@ -3620,6 +3626,8 @@ int	 redraw_client_has_window(struct client *, struct window *);
 void	 redraw_invalidate_scene(struct window *);
 void	 redraw_invalidate_all_scenes(void);
 void	 redraw_damage_window(struct window *, u_int, u_int, u_int, u_int);
+void	 redraw_damage_scroll(struct window *, u_int, u_int, u_int, u_int);
+void	 redraw_scroll_result(struct tty *, const struct tty_ctx *, int);
 void	 redraw_free_damage(struct window *);
 void	 redraw_client_damage(struct client *);
 int	 redraw_get_status_border_cell_type(struct redraw_span **, u_int);

tty.c

@@ -1,4 +1,4 @@
-/* $OpenBSD: tty.c,v 1.488 2026/10/14 11:54:55 nicm Exp $ */
+/* $OpenBSD: tty.c,v 1.489 2026/10/14 12:48:50 nicm Exp $ */
 
 /*
  * Copyright (c) 2007 Nicholas Marriott <nicholas.marriott@gmail.com>
@@ -1669,10 +1669,12 @@ tty_cmd_reverseindex(struct tty *tty, const struct tty_ctx *ctx)
 	    !tty_term_has(tty->term, TTYC_RIN)) ||
 	    ctx->sx == 1 ||
 	    ctx->sy == 1) {
+		redraw_scroll_result(tty, ctx, 1);
 		tty_redraw_region(tty, ctx);
 		return;
 	}
 
+	redraw_scroll_result(tty, ctx, 0);
 	tty_default_attributes(tty, ctx->bg, &ctx->style_ctx);
 
 	tty_region_pane(tty, ctx, ctx->orupper, ctx->orlower);
@@ -1697,10 +1699,12 @@ tty_cmd_linefeed(struct tty *tty, const struct tty_ctx *ctx)
 	    !tty_term_has(tty->term, TTYC_CSR) ||
 	    ctx->sx == 1 ||
 	    ctx->sy == 1) {
+		redraw_scroll_result(tty, ctx, 1);
 		tty_redraw_region(tty, ctx);
 		return;
 	}
 
+	redraw_scroll_result(tty, ctx, 0);
 	tty_default_attributes(tty, ctx->bg, &ctx->style_ctx);
 
 	tty_region_pane(tty, ctx, ctx->orupper, ctx->orlower);
@@ -1735,10 +1739,12 @@ tty_cmd_scrollup(struct tty *tty, const struct tty_ctx *ctx)
 	    !tty_term_has(tty->term, TTYC_CSR) ||
 	    ctx->sx == 1 ||
 	    ctx->sy == 1) {
+		redraw_scroll_result(tty, ctx, 1);
 		tty_redraw_region(tty, ctx);
 		return;
 	}
 
+	redraw_scroll_result(tty, ctx, 0);
 	tty_default_attributes(tty, ctx->bg, &ctx->style_ctx);
 
 	tty_region_pane(tty, ctx, ctx->orupper, ctx->orlower);
@@ -1773,10 +1779,12 @@ tty_cmd_scrolldown(struct tty *tty, const struct tty_ctx *ctx)
 	    !tty_term_has(tty->term, TTYC_RIN)) ||
 	    ctx->sx == 1 ||
 	    ctx->sy == 1) {
+		redraw_scroll_result(tty, ctx, 1);
 		tty_redraw_region(tty, ctx);
 		return;
 	}
 
+	redraw_scroll_result(tty, ctx, 0);
 	tty_default_attributes(tty, ctx->bg, &ctx->style_ctx);
 
 	tty_region_pane(tty, ctx, ctx->orupper, ctx->orlower);