Fix cursor and redraw overlap with auto-hide scrollbars

Auto-hide scrollbars are drawn as overlays inside the pane rather than in
reserved columns. Avoid optimized pane scrolling/redraw paths writing through
a visible overlay scrollbar, and suppress the terminal cursor when it would be
placed in the visible overlay scrollbar column.

This prevents transient wrong-colour cells and cursor blocks appearing over
the scrollbar, especially when scrolling small floating panes.  This fixed
the green block issue.

screen-write.c

@@ -2174,6 +2174,10 @@ screen_write_collect_flush_scrolled(struct screen_write_ctx *ctx)
 		screen_write_redraw_pane(ctx, &ttyctx);
 		return 0;
 	}
+	if (wp != NULL && window_pane_scrollbar_overlay_visible(wp)) {
+		wp->flags |= PANE_REDRAW;
+		return 0;
+	}
 
 	log_debug("%s: scrolled %u (region %u-%u)", __func__, ctx->scrolled,
 	    s->rupper, s->rlower);
@@ -2187,7 +2191,7 @@ screen_write_collect_flush_scrolled(struct screen_write_ctx *ctx)
 	tty_write(tty_cmd_scrollup, &ttyctx);
 
 	if (wp != NULL)
-		wp->flags |= PANE_REDRAWSCROLLBAR;
+		window_pane_scrollbar_redraw(wp);
 	return 1;
 }
 

server-client.c

@@ -1882,7 +1882,7 @@ server_client_reset_state(struct client *c)
 	struct screen		*s = NULL;
 	struct options		*oo = c->session->options;
 	int			 mode = 0, cursor, flags, pane_mode = 0;
-	u_int			 cx = 0, cy = 0, ox, oy, sx, sy, n;
+	u_int			 cx = 0, cy = 0, ox, oy, sx, sy, n, sb_w;
 	struct visible_ranges	*r;
 
 	if (c->flags & (CLIENT_CONTROL|CLIENT_SUSPENDED))
@@ -1942,6 +1942,21 @@ server_client_reset_state(struct client *c)
 			if (!window_position_is_visible(r, cx))
 				cursor = 0;
 
+			if (window_pane_scrollbar_overlay_visible(wp)) {
+				sb_w = wp->scrollbar_style.width;
+				if (sb_w > wp->sx)
+					sb_w = wp->sx;
+				if (sb_w != 0 &&
+				    options_get_number(w->options,
+				    "pane-scrollbars-position") ==
+				    PANE_SCROLLBARS_LEFT) {
+					if (s->cx < sb_w)
+						cursor = 0;
+				} else if (sb_w != 0 &&
+				    s->cx >= wp->sx - sb_w)
+					cursor = 0;
+			}
+
 			if (status_at_line(c) == 0)
 				cy += status_line_size(c);
 		}

tmux.h

@@ -3518,9 +3518,11 @@ int		 window_pane_show_scrollbar(struct window_pane *, int);
 int		 window_pane_scrollbar_reserve(struct window_pane *, int);
 int		 window_pane_scrollbar_visible(struct window_pane *, int);
 int		 window_pane_scrollbar_overlay(struct window_pane *, int);
+int		 window_pane_scrollbar_overlay_visible(struct window_pane *);
 void		 window_pane_scrollbar_show(struct window_pane *, int);
 void		 window_pane_scrollbar_hide(struct window_pane *);
 void		 window_pane_scrollbar_start_timer(struct window_pane *);
+void		 window_pane_scrollbar_redraw(struct window_pane *);
 int		 window_pane_get_bg(struct window_pane *);
 int		 window_pane_get_fg(struct window_pane *);
 int		 window_pane_get_fg_control_client(struct window_pane *);

window-copy.c

@@ -5284,7 +5284,10 @@ window_copy_redraw_lines(struct window_mode_entry *wme, u_int py, u_int ny)
 		return;
 	}
 
-	screen_write_start_pane(&ctx, wp, NULL);
+	if (window_pane_scrollbar_overlay_visible(wp))
+		screen_write_start(&ctx, &data->screen);
+	else
+		screen_write_start_pane(&ctx, wp, NULL);
 	for (i = py; i < py + ny; i++)
 		window_copy_write_line(wme, &ctx, i);
 	screen_write_cursormove(&ctx,
@@ -5292,7 +5295,7 @@ window_copy_redraw_lines(struct window_mode_entry *wme, u_int py, u_int ny)
 	    0);
 	screen_write_stop(&ctx);
 
-	wp->flags |= PANE_REDRAWSCROLLBAR;
+	window_pane_scrollbar_redraw(wp);
 }
 
 static void
@@ -6580,7 +6583,10 @@ window_copy_scroll_up(struct window_mode_entry *wme, u_int ny)
 		return;
 	}
 
-	screen_write_start_pane(&ctx, wp, NULL);
+	if (window_pane_scrollbar_overlay_visible(wp))
+		screen_write_start(&ctx, &data->screen);
+	else
+		screen_write_start_pane(&ctx, wp, NULL);
 	screen_write_cursormove(&ctx, 0, 0, 0);
 	screen_write_deleteline(&ctx, ny, 8);
 	window_copy_write_lines(wme, &ctx, screen_size_y(s) - ny, ny);
@@ -6595,7 +6601,7 @@ window_copy_scroll_up(struct window_mode_entry *wme, u_int ny)
 	    window_copy_cursor_offset(wme, data->cx, screen_size_x(s)), data->cy,
 	    0);
 	screen_write_stop(&ctx);
-	wp->flags |= PANE_REDRAWSCROLLBAR;
+	window_pane_scrollbar_redraw(wp);
 }
 
 static void
@@ -6641,7 +6647,10 @@ window_copy_scroll_down(struct window_mode_entry *wme, u_int ny)
 		return;
 	}
 
-	screen_write_start_pane(&ctx, wp, NULL);
+	if (window_pane_scrollbar_overlay_visible(wp))
+		screen_write_start(&ctx, &data->screen);
+	else
+		screen_write_start_pane(&ctx, wp, NULL);
 	screen_write_cursormove(&ctx, 0, 0, 0);
 	screen_write_insertline(&ctx, ny, 8);
 	window_copy_write_lines(wme, &ctx, 0, ny);
@@ -6652,7 +6661,7 @@ window_copy_scroll_down(struct window_mode_entry *wme, u_int ny)
 	screen_write_cursormove(&ctx, window_copy_cursor_offset(wme, data->cx,
 	    screen_size_x(s)), data->cy, 0);
 	screen_write_stop(&ctx);
-	wp->flags |= PANE_REDRAWSCROLLBAR;
+	window_pane_scrollbar_redraw(wp);
 }
 
 static void

window.c

@@ -1151,8 +1151,28 @@ window_pane_scrollbar_auto_hide(struct window_pane *wp)
 	    "pane-scrollbars-auto-hide"));
 }
 
-static void
+int
+window_pane_scrollbar_overlay_visible(struct window_pane *wp)
+{
+	int	sb;
+
+	sb = options_get_number(wp->window->options, "pane-scrollbars");
+	return (window_pane_scrollbar_overlay(wp, sb) &&
+	    window_pane_scrollbar_visible(wp, sb));
+}
+
+void
 window_pane_scrollbar_redraw(struct window_pane *wp)
+{
+	if (window_pane_scrollbar_overlay_visible(wp)) {
+		wp->flags |= PANE_REDRAW;
+		return;
+	}
+	wp->flags |= PANE_REDRAWSCROLLBAR;
+}
+
+static void
+window_pane_scrollbar_redraw_visibility(struct window_pane *wp)
 {
 	redraw_invalidate_scene(wp->window);
 	wp->flags |= PANE_REDRAW;
@@ -2066,7 +2086,7 @@ window_pane_scrollbar_show(struct window_pane *wp, int start_timer)
 	if (start_timer)
 		window_pane_scrollbar_start_timer(wp);
 	if (changed)
-		window_pane_scrollbar_redraw(wp);
+		window_pane_scrollbar_redraw_visibility(wp);
 }
 
 void
@@ -2078,7 +2098,7 @@ window_pane_scrollbar_hide(struct window_pane *wp)
 	if (!wp->sb_auto_visible)
 		return;
 	wp->sb_auto_visible = 0;
-	window_pane_scrollbar_redraw(wp);
+	window_pane_scrollbar_redraw_visibility(wp);
 }
 
 int