Setting SGR0 when setting the fg and bg has problems if only one of the two is

meant to be default, so rewrite the code to move this outside, move setting
colours before attributes and generally clean up.

Tested by sthen@, fixes problems he was seeing with mutt and should fix some
existing problems with (rarely) lost attributes.

tty.c

@@ -33,8 +33,9 @@ void	tty_fill_acs(struct tty *);
 int	tty_try_256(struct tty *, u_char, const char *);
 int	tty_try_88(struct tty *, u_char, const char *);
 
-void	tty_attributes_fg(struct tty *, const struct grid_cell *);
+void	tty_colours(struct tty *, const struct grid_cell *, int *);
-void	tty_attributes_bg(struct tty *, const struct grid_cell *);
+void	tty_colours_fg(struct tty *, const struct grid_cell *, int *);
+void	tty_colours_bg(struct tty *, const struct grid_cell *, int *);
 
 void	tty_redraw_region(struct tty *, const struct tty_ctx *);
 void	tty_emulate_repeat(
@@ -1120,14 +1121,23 @@ tty_attributes(struct tty *tty, const struct grid_cell *gc)
 {
 	struct grid_cell	*tc = &tty->cell;
 	u_char			 changed;
-	u_int			 fg, bg, attr;
+	u_int			 fg = gc->fg, bg = gc->bg, attr = gc->attr;
+
+	/* If any bits are being cleared, reset everything. */
+	if (tc->attr & ~attr)
+		tty_reset(tty);
+
+	/*
+	 * Set the colours. This may call tty_reset() (so it comes next) and
+	 * may add to the desired attributes in attr.
+	 */
+	tty_colours(tty, gc, &attr);
 
 	/*
 	 * If no setab, try to use the reverse attribute as a best-effort for a
 	 * non-default background. This is a bit of a hack but it doesn't do
 	 * any serious harm and makes a couple of applications happier.
 	 */
-	fg = gc->fg; bg = gc->bg; attr = gc->attr;
 	if (!tty_term_has(tty->term, TTYC_SETAB)) {
 		if (attr & GRID_ATTR_REVERSE) {
 			if (fg != 7 && fg != 8)
@@ -1138,10 +1148,6 @@ tty_attributes(struct tty *tty, const struct grid_cell *gc)
 		}
 	}
 
-	/* If any bits are being cleared, reset everything. */
-	if (tc->attr & ~attr)
-		tty_reset(tty);
-
 	/* Filter out attribute bits already set. */
 	changed = attr & ~tc->attr;
 	tc->attr = attr;
@@ -1167,24 +1173,140 @@ tty_attributes(struct tty *tty, const struct grid_cell *gc)
 		tty_putcode(tty, TTYC_INVIS);
 	if (changed & GRID_ATTR_CHARSET)
 		tty_putcode(tty, TTYC_SMACS);
+}
 
-	/* Set foreground colour. */
+void
-	if (fg != tc->fg ||
+tty_colours(struct tty *tty, const struct grid_cell *gc, int *attr)
-	    (gc->flags & GRID_FLAG_FG256) != (tc->flags & GRID_FLAG_FG256)) {
+{
-		tty_attributes_fg(tty, gc);
+	struct grid_cell	*tc = &tty->cell;
+	u_char			 fg = gc->fg, bg = gc->bg;
+	int			 flags, have_ax;
+	int			 fg_default, bg_default;
+
+	/* No changes? Nothing is necessary. */
+	flags = (gc->flags ^ tc->flags) & (GRID_FLAG_FG256|GRID_FLAG_BG256);
+	if (fg == tc->fg && bg == tc->bg && flags == 0)
+		return;
+
+	/*
+	 * Is either the default colour? This is handled specially because the
+	 * best solution might be to reset both colours to default, in which
+	 * case if only one is default need to fall onward to set the other
+	 * colour.
+	 */
+	fg_default = (fg == 8 && !(gc->flags & GRID_FLAG_FG256));
+	bg_default = (bg == 8 && !(gc->flags & GRID_FLAG_BG256));
+	if (fg_default || bg_default) {
+		/*
+		 * 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
+		 * and sometimes isn't). This resets both colours to default.
+		 *
+		 * Otherwise, try to set the default colour only as needed.
+		 */
+		have_ax = tty_term_has(tty->term, TTYC_AX);
+		if (!have_ax && tty_term_has(tty->term, TTYC_OP))
+			tty_reset(tty);
+		else {
+			if (fg_default &&
+			    fg != tc->fg && !(tc->flags & GRID_FLAG_FG256)) {
+				if (have_ax)
+					tty_puts(tty, "\033[39m");
+				else if (tc->fg != 7)
+					tty_putcode1(tty, TTYC_SETAF, 7);
+				tc->fg = 8;
+				tc->flags &= ~GRID_FLAG_FG256;
+			}
+			if (bg_default &&
+			    bg != tc->bg && !(tc->flags & GRID_FLAG_BG256)) {
+				if (have_ax)					
+					tty_puts(tty, "\033[49m");
+				else if (tc->bg != 0)
+					tty_putcode1(tty, TTYC_SETAB, 0);
+				tc->bg = 8;
+				tc->flags &= ~GRID_FLAG_BG256;
+			}
+		}
+	}
+
+	/* Set the foreground colour. */
+	if (!fg_default && (fg != tc->fg ||
+	    ((gc->flags & GRID_FLAG_FG256) != (tc->flags & GRID_FLAG_FG256))))
+		tty_colours_fg(tty, gc, attr);
+
+	/*
+	 * Set the background colour. This must come after the foreground as
+	 * tty_colour_fg() can call tty_reset().
+	 */
+	if (!bg_default && (bg != tc->bg ||
+	    ((gc->flags & GRID_FLAG_BG256) != (tc->flags & GRID_FLAG_BG256))))
+		tty_colours_bg(tty, gc, attr);
+}
+
+void
+tty_colours_fg(struct tty *tty, const struct grid_cell *gc, int *attr)
+{
+	struct grid_cell	*tc = &tty->cell;
+	u_char			 fg = gc->fg;
+
+	/* Is this a 256-colour colour? */
+	if (gc->flags & GRID_FLAG_FG256) {
+		/* Try as 256 colours or translating to 88. */
+		if (tty_try_256(tty, fg, "38") == 0)
+			goto save_fg;
+		if (tty_try_88(tty, fg, "38") == 0)
+			goto save_fg;
+
+		/* Translate to 16-colour palette, updating bold if needed. */
+		fg = colour_256to16(fg);
+		if (fg & 8) {
+			fg &= 7;
+			(*attr) |= GRID_ATTR_BRIGHT;
+		} else
+			tty_reset(tty);		/* turn off bold */
+	}
+
+	/* Otherwise set the foreground colour. */
+	tty_putcode1(tty, TTYC_SETAF, fg);
+
+save_fg:	
+	/* Save the new values in the terminal current cell. */
 	tc->fg = fg;
 	tc->flags &= ~GRID_FLAG_FG256;
 	tc->flags |= gc->flags & GRID_FLAG_FG256;
+}
+
+void
+tty_colours_bg(struct tty *tty, const struct grid_cell *gc, unused int *attr)
+{
+	struct grid_cell	*tc = &tty->cell;
+	u_char			 bg = gc->bg;
+
+	/* Is this a 256-colour colour? */
+	if (gc->flags & GRID_FLAG_BG256) {
+		/* Try as 256 colours or translating to 88. */
+		if (tty_try_256(tty, bg, "48") == 0)
+			goto save_bg;
+		if (tty_try_88(tty, bg, "48") == 0)
+			goto save_bg;
+
+		/*
+		 * Translate to 16-colour palette. Bold background doesn't
+		 * exist portably, so just discard the bold bit if set.
+		 */
+		bg = colour_256to16(bg);
+		if (bg & 8)
+			bg &= 7;
 	}
 
-	/* Set background colour. */
+	/* Otherwise set the background colour. */
-	if (bg != tc->bg ||
+	tty_putcode1(tty, TTYC_SETAB, bg);
-	    (gc->flags & GRID_FLAG_BG256) != (tc->flags & GRID_FLAG_BG256)) {
+
-		tty_attributes_bg(tty, gc);
+save_bg:
+	/* Save the new values in the terminal current cell. */
 	tc->bg = bg;
 	tc->flags &= ~GRID_FLAG_BG256;
 	tc->flags |= gc->flags & GRID_FLAG_BG256;
-	}
 }
 
 int
@@ -1215,68 +1337,3 @@ tty_try_88(struct tty *tty, u_char colour, const char *type)
 	tty_puts(tty, s);
 	return (0);
 }
-
-void
-tty_attributes_fg(struct tty *tty, const struct grid_cell *gc)
-{
-	u_char	fg;
-
-	fg = gc->fg;
-	if (gc->flags & GRID_FLAG_FG256) {
-		if (tty_try_256(tty, fg, "38") == 0)
-			return;
-		if (tty_try_88(tty, fg, "38") == 0)
-			return;
-		fg = colour_256to16(fg);
-		if (fg & 8) {
-			fg &= 7;
-			tty_putcode(tty, TTYC_BOLD);
-			tty->cell.attr |= GRID_ATTR_BRIGHT;
-		} else if (tty->cell.attr & GRID_ATTR_BRIGHT)
-			tty_reset(tty);
-	}
-
-	if (fg == 8) {
-		if (tty_term_has(tty->term, TTYC_AX)) {
-			/* AX is an extension that means \033[39m works. */
-			tty_puts(tty, "\033[39m");	
-		} else if (tty_term_has(tty->term, TTYC_OP)) {
-			/*
-			 * op can be used to look for default colours but there
-			 * is no point in using it - with some terminals it
-			 * does SGR0 and others not, so SGR0 is needed anyway
-			 * to put the terminal into a known state.
-			 */
-			tty_reset(tty);
-		} else
-			tty_putcode1(tty, TTYC_SETAF, 7);
-	} else
-		tty_putcode1(tty, TTYC_SETAF, fg);
-}
-
-void
-tty_attributes_bg(struct tty *tty, const struct grid_cell *gc)
-{
-	u_char	bg;
-
-	bg = gc->bg;
-	if (gc->flags & GRID_FLAG_BG256) {
-		if (tty_try_256(tty, bg, "48") == 0)
-			return;
-		if (tty_try_88(tty, bg, "48") == 0)
-			return;
-		bg = colour_256to16(bg);
-		if (bg & 8)
-			bg &= 7;
-	}
-
-	if (bg == 8) {
-		if (tty_term_has(tty->term, TTYC_AX)) {
-			tty_puts(tty, "\033[49m");	
-		} else if (tty_term_has(tty->term, TTYC_OP))
-			tty_reset(tty);
-		else
-			tty_putcode1(tty, TTYC_SETAB, 0);
-	} else
-		tty_putcode1(tty, TTYC_SETAB, bg);
-}