When enabling the embedded bitmaps in a truetype font using fontconfig, one has to set both "embeddedbitmap=true" and "antialias=false". The first one does not work without the second one. However there are cases where the font has only partial glyphs have bitmaps, in these cases, if one choose to use those embedded bitmaps, those glyphs that do not have embedded bitmaps will be shown without AA, which is ugly in many cases. You can find an example of this in a recent Ubuntu bug: https://bugs.launchpad.net/ubuntu/+source/ttf-wqy-zenhei/+bug/475240 IMO, embeddedbitmap should work without changing antialias. The best scenario should be setting embeddedbitmap=true will give the embedded bitmaps a higher priority in a glyph-by-glyph basis: if they present, then use them; otherwise, fallback to antialias/hintstyle/autohint settings.
Since fontconfig isn't a rendering library, here is the wrong place to report such things. FWIW looking at the latest cairo code, the embeddedbitmap seems applied only when the antialias is enabled: http://cgit.freedesktop.org/cairo/tree/src/cairo-ft-font.c#n1605 I don't know if it still persist but you better try it again and report it to the rendering library you use.
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