font/freetype: CBDT/CBLC tables imply color

pkg/freetype/face.zig

@@ -135,6 +135,15 @@ pub const Face = struct {
         return buf;
     }
 
+    /// Check whether a given SFNT table is available in a face.
+    pub fn hasSfntTable(self: Face, tag: Tag) bool {
+        const tag_u64: u64 = @intCast(@as(u32, @bitCast(tag)));
+        var len: c_ulong = 0;
+        const res = c.FT_Load_Sfnt_Table(self.handle, tag_u64, 0, null, &len);
+        _ = intToError(res) catch return false;
+        return len != 0;
+    }
+
     /// Retrieve the font variation descriptor for a font.
     pub fn getMMVar(self: Face) Error!*c.FT_MM_Var {
         var result: *c.FT_MM_Var = undefined;

src/font/face/freetype.zig

@@ -216,6 +216,11 @@ pub const Face = struct {
         // sbix table is always true for now
         if (self.face.hasSBIX()) return true;
 
+        // CBDT/CBLC tables always imply colorized glyphs.
+        // These are used by Noto.
+        if (self.face.hasSfntTable(freetype.Tag.init("CBDT"))) return true;
+        if (self.face.hasSfntTable(freetype.Tag.init("CBLC"))) return true;
+
         // Otherwise, load the glyph and see what format it is in.
         self.face.loadGlyph(glyph_id, .{
             .render = true,
@@ -698,6 +703,13 @@ test "color emoji" {
 
     _ = try ft_font.renderGlyph(alloc, &atlas, ft_font.glyphIndex('🥸').?, .{});
 
+    // Make sure this glyph has color
+    {
+        try testing.expect(ft_font.hasColor());
+        const glyph_id = ft_font.glyphIndex('🥸').?;
+        try testing.expect(ft_font.isColorGlyph(glyph_id));
+    }
+
     // resize
     {
         const glyph = try ft_font.renderGlyph(alloc, &atlas, ft_font.glyphIndex('🥸').?, .{