Add a "terminal" colour which can be used instead of "default" in style

options for the terminal default colour, bypassing any inheritance from
other options. Prompted by a discussion with abieber@.

colour.c

@@ -141,6 +141,8 @@ colour_tostring(int c)
 		return ("white");
 	case 8:
 		return ("default");
+	case 9:
+		return ("terminal");
 	case 90:
 		return ("brightblack");
 	case 91:
@@ -188,6 +190,11 @@ colour_fromstring(const char *s)
 		return (n | COLOUR_FLAG_256);
 	}
 
+	if (strcasecmp(s, "default") == 0)
+		return (8);
+	if (strcasecmp(s, "terminal") == 0)
+		return (9);
+
 	if (strcasecmp(s, "black") == 0 || strcmp(s, "0") == 0)
 		return (0);
 	if (strcasecmp(s, "red") == 0 || strcmp(s, "1") == 0)
@@ -204,8 +211,6 @@ colour_fromstring(const char *s)
 		return (6);
 	if (strcasecmp(s, "white") == 0 || strcmp(s, "7") == 0)
 		return (7);
-	if (strcasecmp(s, "default") == 0 || strcmp(s, "8") == 0)
-		return (8);
 	if (strcasecmp(s, "brightblack") == 0 || strcmp(s, "90") == 0)
 		return (90);
 	if (strcasecmp(s, "brightred") == 0 || strcmp(s, "91") == 0)

grid.c

@@ -418,7 +418,7 @@ static void
 grid_empty_line(struct grid *gd, u_int py, u_int bg)
 {
 	memset(&gd->linedata[py], 0, sizeof gd->linedata[py]);
-	if (bg != 8)
+	if (!COLOUR_DEFAULT(bg))
 		grid_expand_line(gd, py, gd->sx, bg);
 }
 
@@ -524,7 +524,8 @@ grid_set_cells(struct grid *gd, u_int px, u_int py, const struct grid_cell *gc,
 void
 grid_clear(struct grid *gd, u_int px, u_int py, u_int nx, u_int ny, u_int bg)
 {
-	u_int	xx, yy;
+	struct grid_line	*gl;
+	u_int			 xx, yy;
 
 	if (nx == 0 || ny == 0)
 		return;
@@ -540,12 +541,13 @@ grid_clear(struct grid *gd, u_int px, u_int py, u_int nx, u_int ny, u_int bg)
 		return;
 
 	for (yy = py; yy < py + ny; yy++) {
-		if (px + nx >= gd->sx && px < gd->linedata[yy].cellused)
-			gd->linedata[yy].cellused = px;
-		if (px > gd->linedata[yy].cellsize && bg == 8)
+		gl = &gd->linedata[yy];
+		if (px + nx >= gd->sx && px < gl->cellused)
+			gl->cellused = px;
+		if (px > gl->cellsize && COLOUR_DEFAULT(bg))
 			continue;
-		if (px + nx >= gd->linedata[yy].cellsize && bg == 8) {
-			gd->linedata[yy].cellsize = px;
+		if (px + nx >= gl->cellsize && COLOUR_DEFAULT(bg)) {
+			gl->cellsize = px;
 			continue;
 		}
 		grid_expand_line(gd, yy, px + nx, 8); /* default bg first */

options-table.c

@@ -771,7 +771,7 @@ const struct options_table_entry options_table[] = {
 	  .type = OPTIONS_TABLE_CHOICE,
 	  .scope = OPTIONS_TABLE_WINDOW,
 	  .choices = options_table_window_size_list,
-	  .default_num = WINDOW_SIZE_LARGEST
+	  .default_num = WINDOW_SIZE_SMALLEST
 	},
 
 	{ .name = "window-style",

screen-write.c

@@ -965,7 +965,7 @@ screen_write_clearline(struct screen_write_ctx *ctx, u_int bg)
 	u_int			 sx = screen_size_x(s);
 
 	gl = grid_get_line(s->grid, s->grid->hsize + s->cy);
-	if (gl->cellsize == 0 && bg == 8)
+	if (gl->cellsize == 0 && COLOUR_DEFAULT(bg))
 		return;
 
 	screen_write_initctx(ctx, &ttyctx);
@@ -988,7 +988,7 @@ screen_write_clearendofline(struct screen_write_ctx *ctx, u_int bg)
 	u_int			 sx = screen_size_x(s);
 
 	gl = grid_get_line(s->grid, s->grid->hsize + s->cy);
-	if (s->cx > sx - 1 || (s->cx >= gl->cellsize && bg == 8))
+	if (s->cx > sx - 1 || (s->cx >= gl->cellsize && COLOUR_DEFAULT(bg)))
 		return;
 
 	screen_write_initctx(ctx, &ttyctx);

tmux.1

@@ -2750,7 +2750,7 @@ Set status line message command style, where
 .Ar style
 is a comma-separated list of characteristics to be specified.
 .Pp
-These may be
+The style format is shared by many options and may be:
 .Ql bg=colour
 to set the background colour,
 .Ql fg=colour
@@ -2773,8 +2773,13 @@ and so on),
 to
 .Ic colour255
 from the 256-colour set,
-.Ic default ,
-or a hexadecimal RGB string such as
+.Ic default
+for the default colour (inherited from another option in the case of some options, for example
+.Ic window-status-style
+inherits from
+.Ic status-style ) ,
+.Ic terminal
+for the terminal default colour, or a hexadecimal RGB string such as
 .Ql #ffffff .
 .Pp
 The attributes is either

tmux.h

@@ -543,6 +543,9 @@ enum utf8_state {
 #define COLOUR_FLAG_256 0x01000000
 #define COLOUR_FLAG_RGB 0x02000000
 
+/* Special colours. */
+#define COLOUR_DEFAULT(c) ((c) == 8 || (c) == 9)
+
 /* Grid attributes. Anything above 0xff is stored in an extended cell. */
 #define GRID_ATTR_BRIGHT 0x1
 #define GRID_ATTR_DIM 0x2

tty.c

@@ -851,7 +851,7 @@ tty_fake_bce(const struct tty *tty, const struct window_pane *wp, u_int bg)
 	if (wp != NULL)
 		tty_default_colours(&gc, wp);
 
-	if (bg != 8 || gc.bg != 8)
+	if (!COLOUR_DEFAULT(bg) || !COLOUR_DEFAULT(gc.bg))
 		return (1);
 	return (0);
 }
@@ -1098,7 +1098,7 @@ tty_clear_area(struct tty *tty, const struct window_pane *wp, u_int py,
 		 * background colour isn't default (because it doesn't work
 		 * after SGR 0).
 		 */
-		if (tty->term_type == TTY_VT420 && bg != 8) {
+		if (tty->term_type == TTY_VT420 && COLOUR_DEFAULT(bg)) {
 			xsnprintf(tmp, sizeof tmp, "\033[32;%u;%u;%u;%u$x",
 			    py + 1, px + 1, py + ny, px + nx);
 			tty_puts(tty, tmp);
@@ -2134,10 +2134,10 @@ tty_attributes(struct tty *tty, const struct grid_cell *gc,
 	 */
 	if (!tty_term_has(tty->term, TTYC_SETAB)) {
 		if (gc2.attr & GRID_ATTR_REVERSE) {
-			if (gc2.fg != 7 && gc2.fg != 8)
+			if (gc2.fg != 7 && !COLOUR_DEFAULT(gc2.fg))
 				gc2.attr &= ~GRID_ATTR_REVERSE;
 		} else {
-			if (gc2.bg != 0 && gc2.bg != 8)
+			if (gc2.bg != 0 && !COLOUR_DEFAULT(gc2.bg))
 				gc2.attr |= GRID_ATTR_REVERSE;
 		}
 	}
@@ -2212,7 +2212,7 @@ tty_colours(struct tty *tty, const struct grid_cell *gc)
 	 * case if only one is default need to fall onward to set the other
 	 * colour.
 	 */
-	if (gc->fg == 8 || gc->bg == 8) {
+	if (COLOUR_DEFAULT(gc->fg) || COLOUR_DEFAULT(gc->bg)) {
 		/*
 		 * If don't have AX but do have op, send sgr0 (op can't
 		 * actually be used because it is sometimes the same as sgr0
@@ -2224,32 +2224,32 @@ tty_colours(struct tty *tty, const struct grid_cell *gc)
 		if (!have_ax && tty_term_has(tty->term, TTYC_OP))
 			tty_reset(tty);
 		else {
-			if (gc->fg == 8 && tc->fg != 8) {
+			if (COLOUR_DEFAULT(gc->fg) && !COLOUR_DEFAULT(tc->fg)) {
 				if (have_ax)
 					tty_puts(tty, "\033[39m");
 				else if (tc->fg != 7)
 					tty_putcode1(tty, TTYC_SETAF, 7);
-				tc->fg = 8;
+				tc->fg = gc->fg;
 			}
-			if (gc->bg == 8 && tc->bg != 8) {
+			if (COLOUR_DEFAULT(gc->bg) && !COLOUR_DEFAULT(tc->bg)) {
 				if (have_ax)
 					tty_puts(tty, "\033[49m");
 				else if (tc->bg != 0)
 					tty_putcode1(tty, TTYC_SETAB, 0);
-				tc->bg = 8;
+				tc->bg = gc->fg;
 			}
 		}
 	}
 
 	/* Set the foreground colour. */
-	if (gc->fg != 8 && gc->fg != tc->fg)
+	if (!COLOUR_DEFAULT(gc->fg) && gc->fg != tc->fg)
 		tty_colours_fg(tty, gc);
 
 	/*
 	 * Set the background colour. This must come after the foreground as
 	 * tty_colour_fg() can call tty_reset().
 	 */
-	if (gc->bg != 8 && gc->bg != tc->bg)
+	if (!COLOUR_DEFAULT(gc->bg) && gc->bg != tc->bg)
 		tty_colours_bg(tty, gc);
 }
 
@@ -2515,9 +2515,11 @@ tty_default_colours(struct grid_cell *gc, const struct window_pane *wp)
 		else
 			gc->fg = wgc->fg;
 
-		if (gc->fg != 8 &&
-		    (c = window_pane_get_palette(wp, gc->fg)) != -1)
-			gc->fg = c;
+		if (gc->fg != 8) {
+			c = window_pane_get_palette(wp, gc->fg);
+			if (c != -1)
+				gc->fg = c;
+		}
 	}
 
 	if (gc->bg == 8) {
@@ -2528,9 +2530,11 @@ tty_default_colours(struct grid_cell *gc, const struct window_pane *wp)
 		else
 			gc->bg = wgc->bg;
 
-		if (gc->bg != 8 &&
-		    (c = window_pane_get_palette(wp, gc->bg)) != -1)
-			gc->bg = c;
+		if (gc->bg != 8) {
+			c = window_pane_get_palette(wp, gc->bg);
+			if (c != -1)
+				gc->bg = c;
+		}
 	}
 }