Add support for (some) colour fonts #30725
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Directly render FT glyphs to the Agg buffer. In particular, this naturally provides, with no extra work, subpixel positioning of glyphs (which could also have been implemented in the old framework, but would have required careful tracking of subpixel offets). Note that all baseline images should be regenerated. The new APIs added to FT2Font are also up to bikeshedding (but they are all private).
anntzer
reviewed
Nov 20, 2025
| self._renderer.draw_image( | ||
| gc, | ||
| bitmap.left, bitmap.top - buffer.shape[0], | ||
| buffer[::-1, :, [2, 1, 0, 3]]) |
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I don't know if we really support big-endian archs, but at least backend_tkcairo uses (2, 1, 0, 3) if sys.byteorder == "little" else (1, 2, 3, 0).
anntzer
reviewed
Nov 20, 2025
| return {{self.bitmap.rows, self.bitmap.width}, | ||
| if (self.bitmap.pixel_mode == FT_PIXEL_MODE_BGRA) { | ||
| return { | ||
| py::array::ShapeContainer({self.bitmap.rows, self.bitmap.width, 4}), |
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Not that it really matters but I think the explicit ShapeContainer and StridesContainer are optional?
This enables loading a non-initial font from collections (`.ttc` files). Currently exposed for `FT2Font`, only.
This should allow listing the metadata from the whole collection, which will also pick the right one if specified, though it will not load the specific index yet.
For backwards-compatibility, the path+index is passed around in a lightweight subclass of `str`.
Note, this only has an effect if set as the global font. Otherwise, just the font name is recorded, and the TeX engine's normal lookup is performed.
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PR summary
This adds support for fonts with colour glyphs supported by FreeType. Specifically, this should mean COLRv0 fonts. There also exist some other colour font types, which are not supported:
We of course do have a full renderer available, but that would require much more interfacing to get working. HarfBuzz (which we use indirectly through libraqm) also has some API for these COLRv1 fonts, but I don't know if it's any nicer to use than FreeType's. Unfortunately, this does exclude one of the most popular emoji fonts, Noto Color Emoji, as that has moved to COLRv1+SVG.
This PR is based on all open font work, because a) #30059 makes it much easier to place the colour data if we don't have to use an intermediate buffer, and b) #30607 due to
FT_Glyph_To_Bitmaplosing colour information and so we need to move to an implementation that usesFT_Render_Glyphdirectly. I also merged #30334 though it's probably not strictly required.For example, we can now render Niklaas in COLRv0, some fonts with simpler decorative effects like Cairo Play, and the older OpenMoji Color that was COLRv0. Fonts that use SVG (like Nabla and Gilbert here) are reduced to their greyscale variant.
PR checklist