So there are probably t2o changes we want to make here: 1) implement a size threshold above which we disable subpixel positioning. If we're already enforcing a font-size limit in WebRender anyway, the glyphs are going to look like mush with subpixel positioning on because of it. Normally when non-WR Skia rendering hits its own internal font size limit, it renders the glyph as a path and disables subpixel positioning for us automagically. So it makes sense to just do this ahead of time down in Gecko when WR is used. 2) we might want to implement some sort of 1-frame lag in pruning glyphs to allow them to not get dumped if we need them that frame.
Bug 1585713 Comment 9 Edit History
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So there are probably two changes we want to make here: 1) implement a size threshold above which we disable subpixel positioning. If we're already enforcing a font-size limit in WebRender anyway, the glyphs are going to look like mush with subpixel positioning on because of it. Normally when non-WR Skia rendering hits its own internal font size limit, it renders the glyph as a path and disables subpixel positioning for us automagically. So it makes sense to just do this ahead of time down in Gecko when WR is used. 2) we might want to implement some sort of 1-frame lag in pruning glyphs to allow them to not get dumped if we need them that frame.