Add support for BCE (background colour erase). This makes various escape

sequences (notable EL and ED but also IL, DL, ICH, DCH) create blank
cells using the current background colour rather than the default
colour.

On modern systems BCE doesn't really have many benefits, but most other
terminals now support it, some (lazy) applications rely on it, and it is
not hard to include now that we have pane background colours anyway.

Mostly written by Sean Haugh.

1 files changed, 63 insertions, 32 deletions

diff --git a/tty.c b/tty.c
index c4adfe82..198b8451 100644
--- a/tty.c
+++ b/tty.c
@@ -55,7 +55,8 @@ static void	tty_colours_bg(struct tty *, const struct grid_cell *);
 static void	tty_region_pane(struct tty *, const struct tty_ctx *, u_int,
 		    u_int);
 static int	tty_large_region(struct tty *, const struct tty_ctx *);
-static int	tty_fake_bce(const struct tty *, const struct window_pane *);
+static int	tty_fake_bce(const struct tty *, const struct window_pane *,
+		    u_int);
 static void	tty_redraw_region(struct tty *, const struct tty_ctx *);
 static void	tty_emulate_repeat(struct tty *, enum tty_code_code,
 		    enum tty_code_code, u_int);
@@ -64,6 +65,8 @@ static void	tty_cell(struct tty *, const struct grid_cell *,
 		    const struct window_pane *);
 static void	tty_default_colours(struct grid_cell *,
 		    const struct window_pane *);
+static void	tty_default_attributes(struct tty *, const struct window_pane *,
+		    u_int);
 
 #define tty_use_acs(tty) \
 	(tty_term_has((tty)->term, TTYC_ACSC) && !((tty)->flags & TTY_UTF8))
@@ -604,17 +607,20 @@ tty_large_region(__unused struct tty *tty, const struct tty_ctx *ctx)
  * emulated.
  */
 static int
-tty_fake_bce(const struct tty *tty, const struct window_pane *wp)
+tty_fake_bce(const struct tty *tty, const struct window_pane *wp, u_int bg)
 {
 	struct grid_cell	gc;
 
+	if (tty_term_flag(tty->term, TTYC_BCE))
+		return (0);
+
 	memcpy(&gc, &grid_default_cell, sizeof gc);
 	if (wp != NULL)
 		tty_default_colours(&gc, wp);
 
-	if (gc.bg == 8)
-		return (0);
-	return (!tty_term_flag(tty->term, TTYC_BCE));
+	if (bg != 8 || gc.bg != 8)
+		return (1);
+	return (0);
 }
 
 /*
@@ -695,13 +701,13 @@ tty_draw_line(struct tty *tty, const struct window_pane *wp,
 	}
 
 	if (sx < tty->sx) {
-		tty_attributes(tty, &grid_default_cell, wp);
+		tty_default_attributes(tty, wp, 8);
 
 		tty_cursor(tty, ox + sx, oy + py);
 		if (sx != screen_size_x(s) &&
 		    ox + screen_size_x(s) >= tty->sx &&
 		    tty_term_has(tty->term, TTYC_EL) &&
-		    !tty_fake_bce(tty, wp))
+		    !tty_fake_bce(tty, wp, 8))
 			tty_putcode(tty, TTYC_EL);
 		else
 			tty_repeat_space(tty, screen_size_x(s) - sx);
@@ -759,14 +765,15 @@ tty_cmd_insertcharacter(struct tty *tty, const struct tty_ctx *ctx)
 {
 	struct window_pane	*wp = ctx->wp;
 
-	if (!tty_pane_full_width(tty, ctx) || tty_fake_bce(tty, wp) ||
-	    (!tty_term_has(tty->term, TTYC_DCH) &&
-	    !tty_term_has(tty->term, TTYC_DCH1))) {
+	if (!tty_pane_full_width(tty, ctx) ||
+	    tty_fake_bce(tty, wp, ctx->bg) ||
+	    (!tty_term_has(tty->term, TTYC_ICH) &&
+	    !tty_term_has(tty->term, TTYC_ICH1))) {
 		tty_draw_pane(tty, wp, ctx->ocy, ctx->xoff, ctx->yoff);
 		return;
 	}
 
-	tty_attributes(tty, &grid_default_cell, wp);
+	tty_default_attributes(tty, wp, ctx->bg);
 
 	tty_cursor_pane(tty, ctx, ctx->ocx, ctx->ocy);
 
@@ -778,14 +785,15 @@ tty_cmd_deletecharacter(struct tty *tty, const struct tty_ctx *ctx)
 {
 	struct window_pane	*wp = ctx->wp;
 
-	if (!tty_pane_full_width(tty, ctx) || tty_fake_bce(tty, wp) ||
+	if (!tty_pane_full_width(tty, ctx) ||
+	    tty_fake_bce(tty, wp, ctx->bg) ||
 	    (!tty_term_has(tty->term, TTYC_DCH) &&
 	    !tty_term_has(tty->term, TTYC_DCH1))) {
 		tty_draw_pane(tty, wp, ctx->ocy, ctx->xoff, ctx->yoff);
 		return;
 	}
 
-	tty_attributes(tty, &grid_default_cell, wp);
+	tty_default_attributes(tty, wp, ctx->bg);
 
 	tty_cursor_pane(tty, ctx, ctx->ocx, ctx->ocy);
 
@@ -801,7 +809,8 @@ tty_cmd_clearcharacter(struct tty *tty, const struct tty_ctx *ctx)
 
 	tty_cursor_pane(tty, ctx, ctx->ocx, ctx->ocy);
 
-	if (tty_term_has(tty->term, TTYC_ECH) && !tty_fake_bce(tty, ctx->wp))
+	if (tty_term_has(tty->term, TTYC_ECH) &&
+	    !tty_fake_bce(tty, ctx->wp, ctx->bg))
 		tty_putcode1(tty, TTYC_ECH, ctx->num);
 	else {
 		for (i = 0; i < ctx->num; i++)
@@ -812,14 +821,15 @@ tty_cmd_clearcharacter(struct tty *tty, const struct tty_ctx *ctx)
 void
 tty_cmd_insertline(struct tty *tty, const struct tty_ctx *ctx)
 {
-	if (!tty_pane_full_width(tty, ctx) || tty_fake_bce(tty, ctx->wp) ||
+	if (!tty_pane_full_width(tty, ctx) ||
+	    tty_fake_bce(tty, ctx->wp, ctx->bg) ||
 	    !tty_term_has(tty->term, TTYC_CSR) ||
 	    !tty_term_has(tty->term, TTYC_IL1)) {
 		tty_redraw_region(tty, ctx);
 		return;
 	}
 
-	tty_attributes(tty, &grid_default_cell, ctx->wp);
+	tty_default_attributes(tty, ctx->wp, ctx->bg);
 
 	tty_region_pane(tty, ctx, ctx->orupper, ctx->orlower);
 	tty_cursor_pane(tty, ctx, ctx->ocx, ctx->ocy);
@@ -830,14 +840,15 @@ tty_cmd_insertline(struct tty *tty, const struct tty_ctx *ctx)
 void
 tty_cmd_deleteline(struct tty *tty, const struct tty_ctx *ctx)
 {
-	if (!tty_pane_full_width(tty, ctx) || tty_fake_bce(tty, ctx->wp) ||
+	if (!tty_pane_full_width(tty, ctx) ||
+	    tty_fake_bce(tty, ctx->wp, ctx->bg) ||
 	    !tty_term_has(tty->term, TTYC_CSR) ||
 	    !tty_term_has(tty->term, TTYC_DL1)) {
 		tty_redraw_region(tty, ctx);
 		return;
 	}
 
-	tty_attributes(tty, &grid_default_cell, ctx->wp);
+	tty_default_attributes(tty, ctx->wp, ctx->bg);
 
 	tty_region_pane(tty, ctx, ctx->orupper, ctx->orlower);
 	tty_cursor_pane(tty, ctx, ctx->ocx, ctx->ocy);
@@ -851,11 +862,12 @@ tty_cmd_clearline(struct tty *tty, const struct tty_ctx *ctx)
 	struct window_pane	*wp = ctx->wp;
 	struct screen		*s = wp->screen;
 
-	tty_attributes(tty, &grid_default_cell, wp);
+	tty_default_attributes(tty, wp, ctx->bg);
 
 	tty_cursor_pane(tty, ctx, 0, ctx->ocy);
 
-	if (tty_pane_full_width(tty, ctx) && !tty_fake_bce(tty, wp) &&
+	if (tty_pane_full_width(tty, ctx) &&
+	    !tty_fake_bce(tty, wp, ctx->bg) &&
 	    tty_term_has(tty->term, TTYC_EL))
 		tty_putcode(tty, TTYC_EL);
 	else
@@ -868,12 +880,13 @@ tty_cmd_clearendofline(struct tty *tty, const struct tty_ctx *ctx)
 	struct window_pane	*wp = ctx->wp;
 	struct screen		*s = wp->screen;
 
-	tty_attributes(tty, &grid_default_cell, wp);
+	tty_default_attributes(tty, wp, ctx->bg);
 
 	tty_cursor_pane(tty, ctx, ctx->ocx, ctx->ocy);
 
 	if (tty_pane_full_width(tty, ctx) &&
-	    tty_term_has(tty->term, TTYC_EL) && !tty_fake_bce(tty, wp))
+	    tty_term_has(tty->term, TTYC_EL) &&
+	    !tty_fake_bce(tty, wp, ctx->bg))
 		tty_putcode(tty, TTYC_EL);
 	else
 		tty_repeat_space(tty, screen_size_x(s) - ctx->ocx);
@@ -882,10 +895,13 @@ tty_cmd_clearendofline(struct tty *tty, const struct tty_ctx *ctx)
 void
 tty_cmd_clearstartofline(struct tty *tty, const struct tty_ctx *ctx)
 {
-	tty_attributes(tty, &grid_default_cell, ctx->wp);
+	struct window_pane	*wp = ctx->wp;
 
-	if (ctx->xoff == 0 && tty_term_has(tty->term, TTYC_EL1) &&
-	    !tty_fake_bce(tty, ctx->wp)) {
+	tty_default_attributes(tty, wp, ctx->bg);
+
+	if (ctx->xoff == 0 &&
+	    tty_term_has(tty->term, TTYC_EL1) &&
+	    !tty_fake_bce(tty, ctx->wp, ctx->bg)) {
 		tty_cursor_pane(tty, ctx, ctx->ocx, ctx->ocy);
 		tty_putcode(tty, TTYC_EL1);
 	} else {
@@ -900,7 +916,8 @@ tty_cmd_reverseindex(struct tty *tty, const struct tty_ctx *ctx)
 	if (ctx->ocy != ctx->orupper)
 		return;
 
-	if (!tty_pane_full_width(tty, ctx) || tty_fake_bce(tty, ctx->wp) ||
+	if (!tty_pane_full_width(tty, ctx) ||
+	    tty_fake_bce(tty, ctx->wp, ctx->bg) ||
 	    !tty_term_has(tty->term, TTYC_CSR) ||
 	    !tty_term_has(tty->term, TTYC_RI)) {
 		tty_redraw_region(tty, ctx);
@@ -923,7 +940,8 @@ tty_cmd_linefeed(struct tty *tty, const struct tty_ctx *ctx)
 	if (ctx->ocy != ctx->orlower)
 		return;
 
-	if (!tty_pane_full_width(tty, ctx) || tty_fake_bce(tty, wp) ||
+	if (!tty_pane_full_width(tty, ctx) ||
+	    tty_fake_bce(tty, wp, ctx->bg) ||
 	    !tty_term_has(tty->term, TTYC_CSR)) {
 		if (tty_large_region(tty, ctx))
 			wp->flags |= PANE_REDRAW;
@@ -955,13 +973,14 @@ tty_cmd_clearendofscreen(struct tty *tty, const struct tty_ctx *ctx)
 	struct screen		*s = wp->screen;
 	u_int			 i, j;
 
-	tty_attributes(tty, &grid_default_cell, wp);
+	tty_default_attributes(tty, wp, ctx->bg);
 
 	tty_region_pane(tty, ctx, 0, screen_size_y(s) - 1);
 	tty_cursor_pane(tty, ctx, ctx->ocx, ctx->ocy);
 
 	if (tty_pane_full_width(tty, ctx) &&
-	    tty_term_has(tty->term, TTYC_EL) && !tty_fake_bce(tty, wp)) {
+	    tty_term_has(tty->term, TTYC_EL) &&
+	    !tty_fake_bce(tty, wp, ctx->bg)) {
 		tty_putcode(tty, TTYC_EL);
 		if (ctx->ocy != screen_size_y(s) - 1) {
 			tty_cursor_pane(tty, ctx, 0, ctx->ocy + 1);
@@ -995,7 +1014,8 @@ tty_cmd_clearstartofscreen(struct tty *tty, const struct tty_ctx *ctx)
 	tty_cursor_pane(tty, ctx, 0, 0);
 
 	if (tty_pane_full_width(tty, ctx) &&
-	    tty_term_has(tty->term, TTYC_EL) && !tty_fake_bce(tty, wp)) {
+	    tty_term_has(tty->term, TTYC_EL) &&
+	    !tty_fake_bce(tty, wp, ctx->bg)) {
 		for (i = 0; i < ctx->ocy; i++) {
 			tty_putcode(tty, TTYC_EL);
 			tty_emulate_repeat(tty, TTYC_CUD, TTYC_CUD1, 1);
@@ -1017,13 +1037,14 @@ tty_cmd_clearscreen(struct tty *tty, const struct tty_ctx *ctx)
 	struct screen		*s = wp->screen;
 	u_int			 i, j;
 
-	tty_attributes(tty, &grid_default_cell, wp);
+	tty_default_attributes(tty, wp, ctx->bg);
 
 	tty_region_pane(tty, ctx, 0, screen_size_y(s) - 1);
 	tty_cursor_pane(tty, ctx, 0, 0);
 
 	if (tty_pane_full_width(tty, ctx) &&
-	    tty_term_has(tty->term, TTYC_EL) && !tty_fake_bce(tty, wp)) {
+	    tty_term_has(tty->term, TTYC_EL) &&
+	    !tty_fake_bce(tty, wp, ctx->bg)) {
 		for (i = 0; i < screen_size_y(s); i++) {
 			tty_putcode(tty, TTYC_EL);
 			if (i != screen_size_y(s) - 1) {
@@ -1721,3 +1742,13 @@ tty_default_colours(struct grid_cell *gc, const struct window_pane *wp)
 			gc->bg = wgc->bg;
 	}
 }
+
+static void
+tty_default_attributes(struct tty *tty, const struct window_pane *wp, u_int bg)
+{
+	static struct grid_cell gc;
+
+	memcpy(&gc, &grid_default_cell, sizeof gc);
+	gc.bg = bg;
+	tty_attributes(tty, &gc, wp);
+}