DWrite: Outermost edges of embedded bitmap font glyphs aren't drawn
Some Japanese fonts contain embedded bitmap fonts for small sizes for readability. For example, MS Gothic and MS Mincho fonts. The embedded bitmap fonts may have slightly different font metrics than the primary vector font.
With DWrite font backend, outermost edges of embedded bitmap font glyphs sometimes aren't drawn. In the following screenshots, WebKit for Windows painted a text "ニコ日" with various font sizes.
DWrite:
GDI: