[paint] Overlay custom-palette on top of chosen palette

Got to agree this is more ergonomic.

src/OT/Color/COLR/COLR.hh

@@ -97,15 +97,13 @@ public:
 
     if (color_index != 0xffff)
     {
-      if (palette_index != HB_PAINT_PALETTE_INDEX_CUSTOM)
+      if (!funcs->custom_palette_color (data, color_index, &color))
       {
 	unsigned int clen = 1;
 	hb_face_t *face = hb_font_get_face (font);
 
 	hb_ot_color_palette_get_colors (face, palette_index, color_index, &clen, &color);
       }
-      else
-	color = funcs->custom_palette_color (data, color_index);
 
       *is_foreground = false;
     }

src/hb-cairo.cc

@@ -306,10 +306,11 @@ hb_cairo_paint_sweep_gradient (hb_paint_funcs_t *pfuncs HB_UNUSED,
   _hb_cairo_paint_sweep_gradient (cr, color_line, x0, y0, start_angle, end_angle);
 }
 
-static hb_color_t
+static hb_bool_t
 hb_cairo_paint_custom_palette_color (hb_paint_funcs_t *funcs,
                                      void *paint_data,
                                      unsigned int color_index,
+                                     hb_color_t *color,
                                      void *user_data HB_UNUSED)
 {
 #ifdef CAIRO_COLOR_PALETTE_CUSTOM
@@ -324,12 +325,13 @@ hb_cairo_paint_custom_palette_color (hb_paint_funcs_t *funcs,
                                                    &red, &green, &blue, &alpha))
   {
     cairo_font_options_destroy (options);
-    return HB_COLOR (255 * blue, 255 * green, 255 * red, 255 * alpha);
+    *color = HB_COLOR (255 * blue, 255 * green, 255 * red, 255 * alpha);
+    return true;
   }
   cairo_font_options_destroy (options);
 #endif
 
-  return HB_COLOR (0, 0, 0, 0);
+  return false;
 }
 
 static inline void free_static_cairo_paint_funcs ();

src/hb-font.cc

@@ -1440,8 +1440,7 @@ hb_font_draw_glyph (hb_font_t *font,
  *
  * If the font has color palettes (see hb_ot_color_has_palettes()),
  * then @palette_index selects the palette to use. If the font only
- * has one palette, this will be 0.  Use %HB_PAINT_PALETTE_INDEX_CUSTOM
+ * has one palette, this will be 0.
- * for custom palette.
  *
  * Since: REPLACEME
  */

src/hb-ft-colr.hh

@@ -156,9 +156,9 @@ _hb_ft_color_line_get_color_stops (hb_color_line_t *color_line,
 				       (hb_color_get_alpha (c->foreground) * stop.color.alpha) >> 14);
       else
       {
-        if (c->palette_index == HB_PAINT_PALETTE_INDEX_CUSTOM)
+	hb_color_t color;
+        if (c->funcs->custom_palette_color (c->data, stop.color.palette_index, &color))
 	{
-	  hb_color_t color = c->funcs->custom_palette_color (c->data, stop.color.palette_index);
 	  color_stops->color = HB_COLOR (hb_color_get_blue (color),
 					 hb_color_get_green (color),
 					 hb_color_get_red (color),
@@ -237,9 +237,8 @@ _hb_ft_paint (hb_ft_paint_context_t *c,
 			  (hb_color_get_alpha (c->foreground) * paint.u.solid.color.alpha) >> 14);
       else
       {
-        if (c->palette_index == HB_PAINT_PALETTE_INDEX_CUSTOM)
+	if (c->funcs->custom_palette_color (c->data, paint.u.solid.color.palette_index, &color))
 	{
-	  color = c->funcs->custom_palette_color (c->data, paint.u.solid.color.palette_index);
 	  color = HB_COLOR (hb_color_get_blue (color),
 			    hb_color_get_green (color),
 			    hb_color_get_red (color),

src/hb-paint.cc

@@ -117,10 +117,11 @@ hb_paint_pop_group_nil (hb_paint_funcs_t *funcs, void *paint_data,
                         hb_paint_composite_mode_t mode,
                         void *user_data) {}
 
-static hb_color_t
+static hb_bool_t
 hb_paint_custom_palette_color_nil (hb_paint_funcs_t *funcs, void *paint_data,
                                    unsigned int color_index,
-                                   void *user_data) { return HB_COLOR(0,0,0,0); }
+                                   hb_color_t *color,
+                                   void *user_data) { return false; }
 
 static bool
 _hb_paint_funcs_set_preamble (hb_paint_funcs_t  *funcs,
@@ -690,11 +691,12 @@ hb_paint_pop_group (hb_paint_funcs_t *funcs, void *paint_data,
  *
  * Since: REPLACEME
  */
-hb_color_t
+hb_bool_t
 hb_paint_custom_palette_color (hb_paint_funcs_t *funcs, void *paint_data,
-                               unsigned int color_index)
+                               unsigned int color_index,
+                               hb_color_t *color)
 {
-  return funcs->custom_palette_color (paint_data, color_index);
+  return funcs->custom_palette_color (paint_data, color_index, color);
 }
 
 #endif

src/hb-paint.h

@@ -34,17 +34,6 @@
 HB_BEGIN_DECLS
 
 
-/**
- * HB_PAINT_PALETTE_INDEX_CUSTOM
- *
- * A palette index signifying that custom colors are in use.
- * Such colors are fetched from the client using the
- * custom-palette-color callback of the paint functions.
- *
- * Since: REPLACEME
- **/
-#define HB_PAINT_PALETTE_INDEX_CUSTOM 0xFFFFFFFF
-
 /**
  * hb_paint_funcs_t:
  *
@@ -680,9 +669,10 @@ typedef void (*hb_paint_pop_group_func_t) (hb_paint_funcs_t *funcs,
  * Return value: the color
  * Since: REPLACEME
  */
-typedef hb_color_t (*hb_paint_custom_palette_color_func_t) (hb_paint_funcs_t *funcs,
+typedef hb_bool_t (*hb_paint_custom_palette_color_func_t) (hb_paint_funcs_t *funcs,
                                                            void *paint_data,
                                                            unsigned int color_index,
+                                                           hb_color_t *color,
                                                            void *user_data);
 
 
@@ -974,9 +964,10 @@ HB_EXTERN void
 hb_paint_pop_group (hb_paint_funcs_t *funcs, void *paint_data,
                     hb_paint_composite_mode_t mode);
 
-HB_EXTERN hb_color_t
+HB_EXTERN hb_bool_t
 hb_paint_custom_palette_color (hb_paint_funcs_t *funcs, void *paint_data,
-                               unsigned int color_index);
+                               unsigned int color_index,
+                               hb_color_t *color);
 
 HB_END_DECLS
 

src/hb-paint.hh

@@ -138,10 +138,12 @@ struct hb_paint_funcs_t
   { func.pop_group (this, paint_data,
                     mode,
                     !user_data ? nullptr : user_data->pop_group); }
-  hb_color_t custom_palette_color (void *paint_data,
+  bool custom_palette_color (void *paint_data,
-                             unsigned int color_index)
+                             unsigned int color_index,
+                             hb_color_t *color)
   { return func.custom_palette_color (this, paint_data,
                                       color_index,
+                                      color,
                                       !user_data ? nullptr : user_data->custom_palette_color); }
 
 

util/helper-cairo.hh

@@ -124,24 +124,22 @@ helper_cairo_create_scaled_font (const font_options_t *font_opts,
   cairo_font_options_set_hint_style (font_options, CAIRO_HINT_STYLE_NONE);
   cairo_font_options_set_hint_metrics (font_options, CAIRO_HINT_METRICS_OFF);
 #ifdef CAIRO_COLOR_PALETTE_DEFAULT
-  unsigned palette_index = view_opts->palette;
+  cairo_font_options_set_color_palette (font_options, view_opts->palette);
+#endif
 #ifdef CAIRO_COLOR_PALETTE_CUSTOM
   if (view_opts->custom_palette)
   {
-    palette_index = HB_PAINT_PALETTE_INDEX_CUSTOM;
     char **entries = g_strsplit (view_opts->custom_palette, ",", -1);
     for (unsigned i = 0; entries[i]; i++)
     {
       unsigned fr, fg, fb, fa;
       fr = fg = fb = fa = 0;
-      parse_color (entries[i], fr, fg,fb, fa);
+      if (parse_color (entries[i], fr, fg,fb, fa))
 	cairo_font_options_set_custom_palette_color (font_options, i, fr / 255., fg / 255., fb / 255., fa / 255.);
     }
     g_strfreev (entries);
   }
 #endif
-  cairo_font_options_set_color_palette (font_options, palette_index);
-#endif
 
   cairo_scaled_font_t *scaled_font = cairo_scaled_font_create (cairo_face,
 							       &font_matrix,