[ot-color] Implement PNGHeader and test it, it doesn't work however

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

@@ -196,23 +196,33 @@ struct sbix
 				    file_type, num_glyphs);
     }
 
+    struct PNGHeader
+    {
+      HBUINT8 header[9];
+      HBUINT32 width;
+      HBUINT32 height;
+    };
+
     inline bool get_png_extents (hb_codepoint_t      glyph,
 				 unsigned int        x_ppem,
 				 unsigned int        y_ppem,
 				 hb_glyph_extents_t *extents) const
     {
+      if (likely (sbix_len == 0))
+        return hb_blob_get_empty ();
+
       int x_offset, y_offset;
       hb_blob_t *blob = reference_blob_for_glyph (glyph, x_ppem, y_ppem,
-						  HB_TAG ('P','N','G',' '),
+						  HB_TAG ('p','n','g',' '),
 						  &x_offset, &y_offset);
-      if (hb_blob_get_length (blob) == 0)
+      if (hb_blob_get_length (blob) < sizeof (PNGHeader))
         return false;
 
       extents->x_bearing = x_offset;
       extents->y_bearing = y_offset;
-      /* XXX: Help me please! */
-      extents->width     = 0;
-      extents->height    = 0;
+      const PNGHeader &header = *blob->as<PNGHeader>();
+      extents->width     = header.width + 100;
+      extents->height    = header.height;
       hb_blob_destroy (blob);
 
       return true;

src/hb-ot-font.cc

@@ -183,9 +183,7 @@ hb_ot_get_glyph_extents (hb_font_t *font,
 			 void *user_data HB_UNUSED)
 {
   const hb_ot_face_data_t *ot_face = (const hb_ot_face_data_t *) font_data;
-  bool ret = false;
-  if (ot_face->sbix->has_data ())
-    ret = ot_face->sbix->get_png_extents (glyph, font->x_ppem, font->y_ppem, extents);
+  bool ret = ot_face->sbix->get_png_extents (glyph, font->x_ppem, font->y_ppem, extents);
   if (!ret)
     ret = ot_face->glyf->get_extents (glyph, extents);
   if (!ret)

test/api/test-ot-color.c

@@ -407,17 +407,28 @@ test_hb_ot_color_png (void)
   hb_blob_t *blob;
   unsigned int length;
   const char *data;
+  hb_glyph_extents_t extents;
 
   /* sbix */
   hb_font_t *sbix_font;
   sbix_font = hb_font_create (sbix);
   blob = hb_ot_color_glyph_reference_png (sbix_font, 0);
+  hb_font_get_glyph_extents (sbix_font, 0, &extents);
+  g_assert_cmpint (extents.x_bearing, ==, 0);
+  g_assert_cmpint (extents.y_bearing, ==, 0);
+  g_assert_cmpint (extents.width, ==, 0);
+  g_assert_cmpint (extents.height, ==, 0);
   g_assert (hb_blob_get_length (blob) == 0);
 
   blob = hb_ot_color_glyph_reference_png (sbix_font, 1);
   data = hb_blob_get_data (blob, &length);
   g_assert_cmpuint (length, ==, 224);
   g_assert (strncmp (data + 1, "PNG", 3) == 0);
+  hb_font_get_glyph_extents (sbix_font, 1, &extents);
+  g_assert_cmpint (extents.x_bearing, ==, 0);
+  g_assert_cmpint (extents.y_bearing, ==, 0);
+  g_assert_cmpint (extents.width, ==, 3501);
+  g_assert_cmpint (extents.height, ==, 20992);
   hb_blob_destroy (blob);
   hb_font_destroy (sbix_font);
 
@@ -431,6 +442,11 @@ test_hb_ot_color_png (void)
   data = hb_blob_get_data (blob, &length);
   g_assert_cmpuint (length, ==, 88);
   g_assert (strncmp (data + 1, "PNG", 3) == 0);
+  hb_font_get_glyph_extents (cbdt_font, 1, &extents);
+  g_assert_cmpint (extents.x_bearing, ==, 0);
+  g_assert_cmpint (extents.y_bearing, ==, 1024);
+  g_assert_cmpint (extents.width, ==, 1024);
+  g_assert_cmpint (extents.height, ==, -1024);
   hb_blob_destroy (blob);
   hb_font_destroy (cbdt_font);
 }