degesch: color cleanup

1 files changed, 79 insertions, 63 deletions

diff --git a/degesch.c b/degesch.c
index 501b63e..a4dbb3e 100644
--- a/degesch.c
+++ b/degesch.c
@@ -1563,40 +1563,6 @@ free_terminal (void)
 	del_curterm (cur_term);
 }
 
-// NOTE: commonly terminals have 8 colors (worst), 16 colors (allows brightness
-//   without the bold/blink attributes), 88 colors (the same plus a 4^3 RGB cube
-//   and a few shades of gray), or 256 colors (best)
-
-static int
-index_to_terminal_palette (int color)
-{
-	hard_assert (color >= 0 && color < 256);
-
-	// No conversion
-	if (max_colors == 256)
-		return color;
-	// These colours are the same everywhere
-	if (color < 16 && max_colors > color)
-		return color;
-
-	// Outside the 16-color range, we only support the 88-color palette,
-	// which we can interpolate to from the 256-color one on input
-	if (max_colors != 88)
-		return -1;
-
-	// 24 -> 8 extra shades of gray
-	if (color >= 232)
-		return 80 + (color - 232) / 3;
-
-	// 6 * 6 * 6 cube -> 4 * 4 * 4 cube
-	int x[6] = { 0, 1, 1, 2, 2, 3 };
-	int index = color - 16;
-	return 16 +
-		( x[ index / 36      ] << 8
-		| x[(index /  6) % 6 ] << 4
-		| x[(index %  6)     ] );
-}
-
 // - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
 
 typedef int (*terminal_printer_fn) (int);
@@ -1726,7 +1692,8 @@ enum
 	ATTRIBUTE_BOLD      = 1 << 0,
 	ATTRIBUTE_ITALIC    = 1 << 1,
 	ATTRIBUTE_UNDERLINE = 1 << 2,
-	ATTRIBUTE_INVERSE   = 1 << 3
+	ATTRIBUTE_INVERSE   = 1 << 3,
+	ATTRIBUTE_BLINK     = 1 << 4
 };
 
 struct attribute_printer
@@ -1773,50 +1740,94 @@ attribute_printer_apply (struct attribute_printer *self, int attribute)
 	}
 }
 
-// TODO: 256-color output
-//   -   8 color -> maybe bold, maybe inverse (should text be bold now?)
-//   -  16 color -> just use the fallback color
-//   -  88 color -> use the 256color value if available
-//   - 256 color -> use the 256color value if available
+// NOTE: commonly terminals have:
+//   8 colors (worst, bright fg with BOLD, bg sometimes with BLINK)
+//   16 colors (okayish, we have the full basic range guaranteed)
+//   88 colors (the same plus a 4^3 RGB cube and a few shades of gray)
+//   256 colors (best, like above but with a larger cube and more gray)
+
+/// Interpolate from the 256-color palette to the 88-color one
+static int
+attribute_printer_256_to_88 (int color)
+{
+	// These colours are the same everywhere
+	if (color < 16)
+		return color;
+
+	// 24 -> 8 extra shades of gray
+	if (color >= 232)
+		return 80 + (color - 232) / 3;
+
+	// 6 * 6 * 6 cube -> 4 * 4 * 4 cube
+	int x[6] = { 0, 1, 1, 2, 2, 3 };
+	int index = color - 16;
+	return 16 +
+		( x[ index / 36      ] << 8
+		| x[(index /  6) % 6 ] << 4
+		| x[(index %  6)     ] );
+}
+
+static int
+attribute_printer_decode_color (int color, bool *is_bright)
+{
+	int16_t c16  = color;        hard_assert (c16  < 16);
+	int16_t c256 = color >> 16;  hard_assert (c256 < 256);
+
+	*is_bright = false;
+	switch (max_colors)
+	{
+	case 8:
+		if (c16 >= 8)
+		{
+			c16 -= 8;
+			*is_bright = true;
+		}
+	case 16:
+		return c16;
+
+	case 88:
+		return c256 <= 0 ? c16 : attribute_printer_256_to_88 (c256);
+	case 256:
+		return c256 <= 0 ? c16 : c256;
+
+	default:
+		// Unsupported palette
+		return -1;
+	}
+}
 
 static void
 attribute_printer_update (struct attribute_printer *self)
 {
-	int fg = 0;
-	if ((int16_t) (self->want_foreground >> 16) > 0)
-		fg = index_to_terminal_palette ((int16_t) (self->want_foreground >> 16));
-	int bg = 0;
-	if ((int16_t) (self->want_background >> 16) > 0)
-		bg = index_to_terminal_palette ((int16_t) (self->want_background >> 16));
-	if (fg <= 0) fg = (int16_t) (self->want_foreground);
-	if (bg <= 0) bg = (int16_t) (self->want_background);
+	bool fg_is_bright;
+	int fg = attribute_printer_decode_color
+		(self->want_foreground, &fg_is_bright);
+	bool bg_is_bright;
+	int bg = attribute_printer_decode_color
+		(self->want_background, &bg_is_bright);
 
+	// TODO: (INVERSE | BOLD) should be used for bright backgrounds
+	//   when possible, i.e. when the foreground shouldn't be bright as well
+	//   and when the BOLD attribute hasn't already been set
 	int attributes = self->want;
-	if (max_colors == 8)
+	if (attributes & ATTRIBUTE_INVERSE)
 	{
-		if (fg >= 8)
-		{
-			attributes |= ATTRIBUTE_BOLD;
-			fg -= 8;
-		}
-		if (bg >= 8)
-		{
-			attributes |= ATTRIBUTE_BOLD;
-			bg -= 8;
-		}
+		bool tmp = fg_is_bright;
+		fg_is_bright = bg_is_bright;
+		bg_is_bright = tmp;
 	}
 
-	attribute_printer_reset (self);
+	if (fg_is_bright) attributes |= ATTRIBUTE_BOLD;
+	if (bg_is_bright) attributes |= ATTRIBUTE_BLINK;
 
-	if (fg >= 0) tputs (g_terminal.color_set_fg[fg], 1, self->printer);
-	if (bg >= 0) tputs (g_terminal.color_set_bg[bg], 1, self->printer);
+	attribute_printer_reset (self);
 
 	if (attributes)
 		tputs (tparm (set_attributes,
 			0, // standout
 			attributes & ATTRIBUTE_UNDERLINE,
 			attributes & ATTRIBUTE_INVERSE,
-			0, // blink
+			attributes & ATTRIBUTE_BLINK,
 			0, // dim
 			attributes & ATTRIBUTE_BOLD,
 			0, // blank
@@ -1824,6 +1835,11 @@ attribute_printer_update (struct attribute_printer *self)
 			0) // acs
 			, 1, self->printer);
 
+	if (fg >= 0)
+		tputs (g_terminal.color_set_fg[fg], 1, self->printer);
+	if (bg >= 0)
+		tputs (g_terminal.color_set_bg[bg], 1, self->printer);
+
 	self->dirty = true;
 }