The latest Windows 10's update (Creators'). In this version GDI get the support of Y-axis anti-aliasing, without fractional advance width. And I've observed that TTFA applied the old GDI hinting strategy to this novel environment, causing it being incorrect. ps. How can i raise a bug to TTFA? It does not have GitHub or things like that.
This problem gets more serious for CFF2: given that the "true bound" of a glyph is not representable in "value + delta" mechanism, and there is no phantom point in CFF2, how can we encode the top side bearing if we want the vertical origin being a fixed, or a simple varible quantity? If we eliminate TSB some rasterizer would make use a constant TSB and make the metrics incorrect.
@Peter Constable I have a question about VVAR: if the point being topmost of a glyph changed after applying a delta, then either TSB or VOrg is not representable in the "value + delta" mechanism. How can we solve this? Prioritize VOrg?