// overwrite a previous bigger alpha with a smaller alpha (in order to avoid
// semi-transparent gaps between joint glyphs with overlapped pixels, which could
// happen, for example, in the RTL text when we copy glyphs from right to left).
// overwrite a previous bigger alpha with a smaller alpha (in order to avoid
// semi-transparent gaps between joint glyphs with overlapped pixels, which could
// happen, for example, in the RTL text when we copy glyphs from right to left).