[cairo] rendering changes cairo 1.16 -> 1.17.4
felix.schwarz at oss.schwarz.eu
Sun Feb 28 22:14:02 UTC 2021
sorry for the late reply - real live/homeschooling/...
Unfortunately I don't have a simple test case but I can reproduce this easily
using WeasyPrint's test suite (e.g. weasyprint/tests/test_draw/test_float.py).
WeasyPrint issue is https://github.com/Kozea/WeasyPrint/issues/1291
I bisected the issue back to this commit:
Author: Matthias Clasen <mclasen at redhat.com>
Date: Sat Jul 28 12:25:47 2018 +0000
image compositor: Support subpixel positioning
Support subpixel positioning with a 4x4 subpixel grid.
When compositing glyphs in the image compositor,
we store the subpixel phases in the high bits of the
glyph index. The _cairo_scaled_glyph_index() macro
has been updated to discard these bits. By storing
the phases in the glyph index, the glyph cache just
keeps working. When loading a glyph, the Freetype
font backend shifts the outline according to the
If I revert that commit on master the tests do pass (while they fail when
building current master - 553c19df)
Does that ring a bell? Any obvious thing I should look out for?
I noticed issue 390 ("subpixel-positioned text strings appear to have a row of
pixels cropped out, sometimes") in gitlab:
That issue also mentions commit ea932921 and Dejavu (which I think
WeasyPrint's test suite uses as well - though I think it might not be an issue
for the failing test).
Anything else I can do besides creating a simple test case? (I tried that
before but it is quite challenging because I have to dig deep through various
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