[paint] Preserve foreground information

src/OT/glyf/glyf.hh

@@ -338,7 +338,7 @@ struct glyf_accelerator_t
     funcs->push_root_transform (data, font);
 
     funcs->push_clip_glyph (data, gid, font);
-    funcs->color (data, foreground);
+    funcs->color (data, true, foreground);
     funcs->pop_clip (data);
 
     funcs->pop_root_transform (data);

src/hb-ot-cff1-table.cc

@@ -558,7 +558,7 @@ bool OT::cff1::accelerator_t::paint_glyph (hb_font_t *font, hb_codepoint_t glyph
   funcs->push_root_transform (data, font);
 
   funcs->push_clip_glyph (data, glyph, font);
-  funcs->color (data, foreground);
+  funcs->color (data, true, foreground);
   funcs->pop_clip (data);
 
   funcs->pop_root_transform (data);

src/hb-ot-cff2-table.cc

@@ -148,7 +148,7 @@ bool OT::cff2::accelerator_t::paint_glyph (hb_font_t *font, hb_codepoint_t glyph
   funcs->push_root_transform (data, font);
 
   funcs->push_clip_glyph (data, glyph, font);
-  funcs->color (data, foreground);
+  funcs->color (data, true, foreground);
   funcs->pop_clip (data);
 
   funcs->pop_root_transform (data);

src/hb-ot-color-colr-table.hh

@@ -97,16 +97,19 @@ public:
     instancer (instancer_)
   { }
 
-  hb_color_t get_color (unsigned int color_index, float alpha)
+  hb_color_t get_color (unsigned int color_index, float alpha, hb_bool_t *is_foreground)
   {
     hb_color_t color = foreground;
 
+    *is_foreground = true;
+
     if (color_index != 0xffff)
     {
       unsigned int clen = 1;
       hb_face_t *face = hb_font_get_face (font);
 
       hb_ot_color_palette_get_colors (face, palette, color_index, &clen, &color);
+      *is_foreground = false;
     }
 
     return HB_COLOR (hb_color_get_blue (color),
@@ -360,7 +363,9 @@ struct ColorStop
 		       const VarStoreInstancer &instancer) const
   {
     out->offset = stopOffset.to_float(instancer (varIdx, 0));
-    out->color = c->get_color (paletteIndex, alpha.to_float (instancer (varIdx, 1)));
+    out->color = c->get_color (paletteIndex,
+                               alpha.to_float (instancer (varIdx, 1)),
+                               &out->is_foreground);
   }
 
   F2DOT14	stopOffset;
@@ -576,9 +581,13 @@ struct PaintSolid
 
   void paint_glyph (hb_paint_context_t *c, uint32_t varIdxBase) const
   {
-    c->funcs->color (c->data,
-                     c->get_color (paletteIndex,
-                                   alpha.to_float (c->instancer (varIdxBase, 0))));
+    hb_bool_t is_foreground;
+    hb_color_t color;
+
+    color = c->get_color (paletteIndex,
+                          alpha.to_float (c->instancer (varIdxBase, 0)),
+                          &is_foreground);
+    c->funcs->color (c->data, is_foreground, color);
   }
 
   HBUINT8	format; /* format = 2(noVar) or 3(Var)*/
@@ -1992,8 +2001,10 @@ struct COLR
       for (const auto &r : (this+layersZ).as_array (numLayers)
 			   .sub_array (record->firstLayerIdx, record->numLayers))
       {
+        hb_bool_t is_foreground;
+        hb_color_t color = c.get_color (r.colorIdx, 1., &is_foreground);
         c.funcs->push_clip_glyph (c.data, r.glyphId, c.font);
-        c.funcs->color (c.data, c.get_color (r.colorIdx, 1.));
+        c.funcs->color (c.data, is_foreground, color);
         c.funcs->pop_clip (c.data);
       }
 

src/hb-paint.cc

@@ -70,6 +70,7 @@ hb_paint_pop_clip_nil (hb_paint_funcs_t *funcs, void *paint_data,
 
 static void
 hb_paint_color_nil (hb_paint_funcs_t *funcs, void *paint_data,
+                    hb_bool_t is_foreground,
                     hb_color_t color,
                     void *user_data) {}
 

src/hb-paint.h

@@ -209,6 +209,7 @@ typedef void (*hb_paint_pop_clip_func_t) (hb_paint_funcs_t *funcs,
  * hb_paint_color_func_t:
  * @funcs: paint functions object
  * @paint_data: The data accompanying the paint functions in hb_font_paint_glyph()
+ * @is_foreground: whether the color is the foreground
  * @color: The color to use
  * @user_data: User data pointer passed to hb_paint_funcs_set_color_func()
  *
@@ -219,6 +220,7 @@ typedef void (*hb_paint_pop_clip_func_t) (hb_paint_funcs_t *funcs,
  */
 typedef void (*hb_paint_color_func_t) (hb_paint_funcs_t *funcs,
                                        void *paint_data,
+                                       hb_bool_t is_foreground,
                                        hb_color_t color,
                                        void *user_data);
 
@@ -277,6 +279,7 @@ typedef struct hb_color_line_t hb_color_line_t;
 /**
  * hb_color_stop_t:
  * @offset: the offset of the color stop
+ * @is_foreground: whether the color is the foreground
  * @color: the color
  *
  * Information about a color stop on a color line.
@@ -288,6 +291,7 @@ typedef struct hb_color_line_t hb_color_line_t;
  */
 typedef struct {
   float offset;
+  hb_bool_t is_foreground;
   hb_color_t color;
 } hb_color_stop_t;
 

src/hb-paint.hh

@@ -92,9 +92,10 @@ struct hb_paint_funcs_t
   { func.pop_clip (this, paint_data,
                    !user_data ? nullptr : user_data->pop_clip); }
   void color (void *paint_data,
+              hb_bool_t is_foreground,
               hb_color_t color)
   { func.color (this, paint_data,
-                color,
+                is_foreground, color,
                 !user_data ? nullptr : user_data->color); }
   void image (void *paint_data,
               hb_blob_t *image,

test/api/test-ot-color.c

@@ -542,6 +542,7 @@ pop_clip (hb_paint_funcs_t *funcs,
 static void
 paint_color (hb_paint_funcs_t *funcs,
              void *paint_data,
+             hb_bool_t use_foreground,
              hb_color_t color,
              void *user_data)
 {

util/helper-cairo-user.hh

@@ -203,6 +203,7 @@ pop_group (hb_paint_funcs_t *funcs,
 static void
 paint_color (hb_paint_funcs_t *funcs,
              void *paint_data,
+             hb_bool_t use_foreground,
              hb_color_t color,
              void *user_data)
 {