[COLR/cairo] Add paint_color_glyph func

Implement in cairo to use scaled-font's glyph cache.

src/OT/Color/COLR/COLR.hh

@@ -2436,6 +2436,10 @@ void PaintColrLayers::paint_glyph (hb_paint_context_t *c) const
 void PaintColrGlyph::paint_glyph (hb_paint_context_t *c) const
 {
   TRACE_PAINT (this);
+
+  if (c->funcs->color_glyph (c->data, gid, c->font))
+    return;
+
   const COLR *colr_table = c->get_colr_table ();
   const Paint *paint = colr_table->get_base_glyph_paint (gid);
 

src/hb-cairo.cc

@@ -166,6 +166,24 @@ hb_cairo_pop_transform (hb_paint_funcs_t *pfuncs HB_UNUSED,
   cairo_restore (cr);
 }
 
+static hb_bool_t
+hb_cairo_paint_color_glyph (hb_paint_funcs_t *pfuncs HB_UNUSED,
+			    void *paint_data,
+			    hb_codepoint_t glyph,
+			    hb_font_t *font,
+			    void *user_data HB_UNUSED)
+{
+  hb_cairo_context_t *c = (hb_cairo_context_t *) paint_data;
+  cairo_t *cr = c->cr;
+
+  cairo_glyph_t cairo_glyph = { glyph, 0, 0 };
+  cairo_set_scaled_font (cr, c->scaled_font);
+  cairo_set_font_size (cr, hb_face_get_upem (hb_font_get_face (font)));
+  cairo_show_glyphs (cr, &cairo_glyph, 1);
+
+  return true;
+}
+
 static void
 hb_cairo_push_clip_glyph (hb_paint_funcs_t *pfuncs HB_UNUSED,
 			  void *paint_data,
@@ -397,6 +415,7 @@ static struct hb_cairo_paint_funcs_lazy_loader_t : hb_paint_funcs_lazy_loader_t<
 
     hb_paint_funcs_set_push_transform_func (funcs, hb_cairo_push_transform, nullptr, nullptr);
     hb_paint_funcs_set_pop_transform_func (funcs, hb_cairo_pop_transform, nullptr, nullptr);
+    hb_paint_funcs_set_color_glyph_func (funcs, hb_cairo_paint_color_glyph, nullptr, nullptr);
     hb_paint_funcs_set_push_clip_glyph_func (funcs, hb_cairo_push_clip_glyph, nullptr, nullptr);
     hb_paint_funcs_set_push_clip_rectangle_func (funcs, hb_cairo_push_clip_rectangle, nullptr, nullptr);
     hb_paint_funcs_set_pop_clip_func (funcs, hb_cairo_pop_clip, nullptr, nullptr);

src/hb-paint.cc

@@ -54,6 +54,12 @@ static void
 hb_paint_pop_transform_nil (hb_paint_funcs_t *funcs, void *paint_data,
                             void *user_data) {}
 
+static hb_bool_t
+hb_paint_color_glyph_nil (hb_paint_funcs_t *funcs, void *paint_data,
+                          hb_codepoint_t glyph,
+                          hb_font_t *font,
+                          void *user_data) { return false; }
+
 static void
 hb_paint_push_clip_glyph_nil (hb_paint_funcs_t *funcs, void *paint_data,
                               hb_codepoint_t glyph,
@@ -473,6 +479,25 @@ hb_paint_pop_transform (hb_paint_funcs_t *funcs, void *paint_data)
   funcs->pop_transform (paint_data);
 }
 
+/**
+ * hb_paint_color_glyph:
+ * @funcs: paint functions
+ * @paint_data: associated data passed by the caller
+ * @glyph: the glyph ID
+ * @font: the font
+ *
+ * Perform a "color-glyph" paint operation.
+ *
+ * XSince: REPLACEME
+ */
+hb_bool_t
+hb_paint_color_glyph (hb_paint_funcs_t *funcs, void *paint_data,
+                      hb_codepoint_t glyph,
+                      hb_font_t *font)
+{
+  return funcs->color_glyph (paint_data, glyph, font);
+}
+
 /**
  * hb_paint_push_clip_glyph:
  * @funcs: paint functions

src/hb-paint.h

@@ -136,6 +136,35 @@ typedef void (*hb_paint_pop_transform_func_t) (hb_paint_funcs_t *funcs,
                                                void *paint_data,
                                                void *user_data);
 
+/**
+ * hb_paint_color_glyph_func_t:
+ * @funcs: paint functions object
+ * @paint_data: The data accompanying the paint functions in hb_font_paint_glyph()
+ * @glyph: the glyph ID
+ * @font: the font
+ * @user_data: User data pointer passed to hb_paint_funcs_set_color_glyph_func()
+ *
+ * A virtual method for the #hb_paint_funcs_t to render a color glyph by glyph index.
+ *
+ * XXX
+ *
+ * The coordinates of the glyph outline are interpreted according
+ * to the current transform.
+ *
+ * This clip is applied in addition to the current clip,
+ * and remains in effect until a matching call to
+ * the #hb_paint_funcs_pop_clip_func_t vfunc.
+ *
+ * Return value: %true if the glyph was painted, %false otherwise.
+ *
+ * XSince: REPLACEME
+ */
+typedef hb_bool_t (*hb_paint_color_glyph_func_t) (hb_paint_funcs_t *funcs,
+                                                  void *paint_data,
+                                                  hb_codepoint_t glyph,
+                                                  hb_font_t *font,
+                                                  void *user_data);
+
 /**
  * hb_paint_push_clip_glyph_func_t:
  * @funcs: paint functions object
@@ -723,6 +752,23 @@ hb_paint_funcs_set_pop_transform_func (hb_paint_funcs_t              *funcs,
                                        void                          *user_data,
                                        hb_destroy_func_t              destroy);
 
+/**
+ * hb_paint_funcs_set_color_glyph_func:
+ * @funcs: A paint functions struct
+ * @func: (closure user_data) (destroy destroy) (scope notified): The color-glyph callback
+ * @user_data: Data to pass to @func
+ * @destroy: (nullable): Function to call when @user_data is no longer needed
+ *
+ * Sets the color-glyph callback on the paint functions struct.
+ *
+ * Since: 7.0.0
+ */
+HB_EXTERN void
+hb_paint_funcs_set_color_glyph_func (hb_paint_funcs_t                *funcs,
+				     hb_paint_color_glyph_func_t     func,
+				     void                            *user_data,
+				     hb_destroy_func_t                destroy);
+
 /**
  * hb_paint_funcs_set_push_clip_glyph_func:
  * @funcs: A paint functions struct
@@ -922,6 +968,11 @@ hb_paint_push_transform (hb_paint_funcs_t *funcs, void *paint_data,
 HB_EXTERN void
 hb_paint_pop_transform (hb_paint_funcs_t *funcs, void *paint_data);
 
+HB_EXTERN hb_bool_t
+hb_paint_color_glyph (hb_paint_funcs_t *funcs, void *paint_data,
+                      hb_codepoint_t glyph,
+                      hb_font_t *font);
+
 HB_EXTERN void
 hb_paint_push_clip_glyph (hb_paint_funcs_t *funcs, void *paint_data,
                           hb_codepoint_t glyph,

src/hb-paint.hh

@@ -32,6 +32,7 @@
 #define HB_PAINT_FUNCS_IMPLEMENT_CALLBACKS \
   HB_PAINT_FUNC_IMPLEMENT (push_transform) \
   HB_PAINT_FUNC_IMPLEMENT (pop_transform) \
+  HB_PAINT_FUNC_IMPLEMENT (color_glyph) \
   HB_PAINT_FUNC_IMPLEMENT (push_clip_glyph) \
   HB_PAINT_FUNC_IMPLEMENT (push_clip_rectangle) \
   HB_PAINT_FUNC_IMPLEMENT (pop_clip) \
@@ -77,6 +78,13 @@ struct hb_paint_funcs_t
   void pop_transform (void *paint_data)
   { func.pop_transform (this, paint_data,
                         !user_data ? nullptr : user_data->pop_transform); }
+  bool color_glyph (void *paint_data,
+                    hb_codepoint_t glyph,
+                    hb_font_t *font)
+  { return func.color_glyph (this, paint_data,
+                             glyph,
+                             font,
+                             !user_data ? nullptr : user_data->push_clip_glyph); }
   void push_clip_glyph (void *paint_data,
                         hb_codepoint_t glyph,
                         hb_font_t *font)