[COLR] Enable COLRv0 support in get_extents()

paint_glyph() supports COLRv0 but this code is never reached because of
the early return if version is not 1. This early return seems to be from
before COLRv0 extents were supported.

src/OT/Color/COLR/COLR.hh

@@ -2058,7 +2058,7 @@ struct delta_set_index_map_subset_plan_t
       unsigned outer = (*var_idx) >> 16;
       unsigned bit_count = (outer == 0) ? 1 : hb_bit_storage (outer);
       outer_bit_count = hb_max (bit_count, outer_bit_count);
-      
+
       unsigned inner = (*var_idx) & 0xFFFF;
       bit_count = (inner == 0) ? 1 : hb_bit_storage (inner);
       inner_bit_count = hb_max (bit_count, inner_bit_count);
@@ -2505,17 +2505,17 @@ struct COLR
   bool
   get_extents (hb_font_t *font, hb_codepoint_t glyph, hb_glyph_extents_t *extents) const
   {
-    if (version != 1)
-      return false;
-
-    ItemVarStoreInstancer instancer (&(this+varStore),
-				 &(this+varIdxMap),
-				 hb_array (font->coords, font->num_coords));
-
-    if (get_clip (glyph, extents, instancer))
+    if (version == 1)
     {
-      font->scale_glyph_extents (extents);
-      return true;
+      ItemVarStoreInstancer instancer (&(this+varStore),
+                                      &(this+varIdxMap),
+                                      hb_array (font->coords, font->num_coords));
+
+      if (get_clip (glyph, extents, instancer))
+      {
+        font->scale_glyph_extents (extents);
+        return true;
+      }
     }
 
     auto *extents_funcs = hb_paint_extents_get_funcs ();
@@ -2570,8 +2570,8 @@ struct COLR
   bool
   paint_glyph (hb_font_t *font, hb_codepoint_t glyph, hb_paint_funcs_t *funcs, void *data, unsigned int palette_index, hb_color_t foreground, bool clip = true) const
   {
-    ItemVarStoreInstancer instancer (&(this+varStore),
-	                         &(this+varIdxMap),
+    ItemVarStoreInstancer instancer (varStore ? &(this+varStore): nullptr,
+	                         varIdxMap ? &(this+varIdxMap): nullptr,
 	                         hb_array (font->coords, font->num_coords));
     hb_paint_context_t c (this, funcs, data, font, palette_index, foreground, instancer);
     c.current_glyphs.add (glyph);

test/api/test-extents.c

@@ -28,7 +28,7 @@
 
 
 static void
-test_glyph_extents (void)
+test_glyph_extents_color_v1 (void)
 {
   hb_face_t *face;
   hb_font_t *font;
@@ -93,12 +93,41 @@ test_glyph_extents (void)
   hb_face_destroy (face);
 }
 
+
+static void
+test_glyph_extents_color_v0 (void)
+{
+  hb_face_t *face;
+  hb_font_t *font;
+  hb_glyph_extents_t extents;
+  hb_bool_t ret;
+
+  /*
+   * This font contains a COLRv0 glyph with an empty default glyph
+   * to make sure we are getting extents from the COLRv0 layers.
+   */
+
+  face = hb_test_open_font_file ("fonts/COLRv0.extents.ttf");
+  font = hb_font_create (face);
+
+  ret = hb_font_get_glyph_extents (font, 13, &extents);
+  g_assert_true (ret);
+  g_assert_true (extents.x_bearing == 192 &&
+                 extents.y_bearing == 573 &&
+                 extents.width     == 731 &&
+                 extents.height    == -758);
+
+  hb_font_destroy (font);
+  hb_face_destroy (face);
+}
+
 int
 main (int argc, char **argv)
 {
   hb_test_init (&argc, &argv);
 
-  hb_test_add (test_glyph_extents);
+  hb_test_add (test_glyph_extents_color_v1);
+  hb_test_add (test_glyph_extents_color_v0);
 
   return hb_test_run();
 }