Move the code to set up a padding cell into grid.c.

grid-view.c

@@ -45,6 +45,13 @@ grid_view_set_cell(struct grid *gd, u_int px, u_int py,
 	grid_set_cell(gd, grid_view_x(gd, px), grid_view_y(gd, py), gc);
 }
 
+/* Set padding. */
+void
+grid_view_set_padding(struct grid *gd, u_int px, u_int py)
+{
+	grid_set_padding(gd, grid_view_x(gd, px), grid_view_y(gd, py));
+}
+
 /* Set cells. */
 void
 grid_view_set_cells(struct grid *gd, u_int px, u_int py,

grid.c

@@ -40,8 +40,16 @@ const struct grid_cell grid_default_cell = {
 	{ { ' ' }, 0, 1, 1 }, 0, 0, 8, 8, 0
 };
 
+/*
+ * Padding grid cell data. Padding cells are the only zero width cell that
+ * appears in the grid - because of this, they are always extended cells.
+ */
+static const struct grid_cell grid_padding_cell = {
+	{ { '!' }, 0, 0, 0 }, 0, GRID_FLAG_PADDING, 8, 8, 0
+};
+
 /* Cleared grid cell data. */
-const struct grid_cell grid_cleared_cell = {
+static const struct grid_cell grid_cleared_cell = {
 	{ { ' ' }, 0, 1, 1 }, 0, GRID_FLAG_CLEARED, 8, 8, 0
 };
 static const struct grid_cell_entry grid_cleared_entry = {
@@ -524,7 +532,7 @@ grid_get_cell(struct grid *gd, u_int px, u_int py, struct grid_cell *gc)
 		grid_get_cell1(&gd->linedata[py], px, gc);
 }
 
-/* Set cell at relative position. */
+/* Set cell at position. */
 void
 grid_set_cell(struct grid *gd, u_int px, u_int py, const struct grid_cell *gc)
 {
@@ -547,7 +555,14 @@ grid_set_cell(struct grid *gd, u_int px, u_int py, const struct grid_cell *gc)
 		grid_store_cell(gce, gc, gc->data.data[0]);
 }
 
-/* Set cells at relative position. */
+/* Set padding at position. */
+void
+grid_set_padding(struct grid *gd, u_int px, u_int py)
+{
+	grid_set_cell(gd, px, py, &grid_padding_cell);
+}
+
+/* Set cells at position. */
 void
 grid_set_cells(struct grid *gd, u_int px, u_int py, const struct grid_cell *gc,
     const char *s, size_t slen)

screen-write.c

@@ -38,10 +38,6 @@ static int	screen_write_overwrite(struct screen_write_ctx *,
 static const struct grid_cell *screen_write_combine(struct screen_write_ctx *,
 		    const struct utf8_data *, u_int *);
 
-static const struct grid_cell screen_write_pad_cell = {
-	{ { 0 }, 0, 0, 0 }, 0, GRID_FLAG_PADDING, 8, 8, 0
-};
-
 struct screen_write_collect_item {
 	u_int			 x;
 	int			 wrapped;
@@ -1774,7 +1770,7 @@ screen_write_cell(struct screen_write_ctx *ctx, const struct grid_cell *gc)
 	 */
 	for (xx = s->cx + 1; xx < s->cx + width; xx++) {
 		log_debug("%s: new padding at %u,%u", __func__, xx, s->cy);
-		grid_view_set_cell(gd, xx, s->cy, &screen_write_pad_cell);
+		grid_view_set_padding(gd, xx, s->cy);
 		skip = 0;
 	}
 

tmux.h

@@ -2499,6 +2499,7 @@ void	 grid_clear_history(struct grid *);
 const struct grid_line *grid_peek_line(struct grid *, u_int);
 void	 grid_get_cell(struct grid *, u_int, u_int, struct grid_cell *);
 void	 grid_set_cell(struct grid *, u_int, u_int, const struct grid_cell *);
+void	 grid_set_padding(struct grid *, u_int, u_int);
 void	 grid_set_cells(struct grid *, u_int, u_int, const struct grid_cell *,
 	     const char *, size_t);
 struct grid_line *grid_get_line(struct grid *, u_int);
@@ -2520,6 +2521,7 @@ u_int	 grid_line_length(struct grid *, u_int);
 void	 grid_view_get_cell(struct grid *, u_int, u_int, struct grid_cell *);
 void	 grid_view_set_cell(struct grid *, u_int, u_int,
 	     const struct grid_cell *);
+void	 grid_view_set_padding(struct grid *, u_int, u_int);
 void	 grid_view_set_cells(struct grid *, u_int, u_int,
 	     const struct grid_cell *, const char *, size_t);
 void	 grid_view_clear_history(struct grid *, u_int);

tty.c

@@ -1380,9 +1380,10 @@ tty_draw_line(struct tty *tty, struct screen *s, u_int px, u_int py, u_int nx,
 			screen_select_cell(s, &last, gcp);
 		else
 			memcpy(&last, gcp, sizeof last);
-		if (!tty_check_overlay(tty, atx + ux, aty))
+		if (!tty_check_overlay(tty, atx + ux, aty)) {
-			ux += gcp->data.width;
+			if (~gcp->flags & GRID_FLAG_PADDING)
-		else if (ux + gcp->data.width > nx) {
+				ux += gcp->data.width;
+		} else if (ux + gcp->data.width > nx) {
 			tty_attributes(tty, &last, defaults, palette);
 			tty_cursor(tty, atx + ux, aty);
 			for (j = 0; j < gcp->data.width; j++) {
@@ -1397,7 +1398,7 @@ tty_draw_line(struct tty *tty, struct screen *s, u_int px, u_int py, u_int nx,
 			for (j = 0; j < gcp->data.size; j++)
 				tty_putc(tty, gcp->data.data[j]);
 			ux += gcp->data.width;
-		} else {
+		} else if (~gcp->flags & GRID_FLAG_PADDING) {
 			memcpy(buf + len, gcp->data.data, gcp->data.size);
 			len += gcp->data.size;
 			width += gcp->data.width;