Fit a glyph that a fallback face draws wider than its cells #10

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natsukium merged 1 commit from fix/fit-overwide-glyphs into main 2026-10-03 11:50:52 +09:00

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natsukium commented 2026-10-01 12:04:19 +09:00

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An East Asian Ambiguous character such as ※ is one cell wide, but a CJK fallback face draws it full-width, so a run of them overlapped into an unreadable smear. Text-presentation emoji from the color face (☺) overflowed the same way.

A glyph whose advance overruns the block it is placed in (its grid width or OSC 66 w, times the cell width, times s) is now rasterized at the size where its ink fits the block, and centred in it. Sizing by the ink rather than the advance keeps a fitted ※ about as large as in kitty and WezTerm. Primary-face text keeps its size at every OSC 66 scale. Multi-codepoint clusters are tracked in #17.

An East Asian Ambiguous character such as `※` is one cell wide, but a CJK fallback face draws it full-width, so a run of them overlapped into an unreadable smear. Text-presentation emoji from the color face (`☺`) overflowed the same way. A glyph whose advance overruns the block it is placed in (its grid width or OSC 66 `w`, times the cell width, times `s`) is now rasterized at the size where its ink fits the block, and centred in it. Sizing by the ink rather than the advance keeps a fitted `※` about as large as in kitty and WezTerm. Primary-face text keeps its size at every OSC 66 scale. Multi-codepoint clusters are tracked in #17.

fit-glyphs-before-after.png

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natsukium added 1 commit 2026-10-01 12:04:19 +09:00

render: shrink a glyph whose advance overruns its cells ... 5e89f771fc

An East Asian Ambiguous character such as U+203B (※) is one cell wide
in the grid, but when the primary face lacks it the CJK fallback face
draws it full-width, so every ※ covered half of its right neighbour and
a run of them rendered as an unreadable smear. Text-presentation emoji
resolved to the color face (☺) overflowed the same way.

The per-char raster path now compares the face's advance with the block
the renderer places the glyph in (grid width or OSC 66 `w`, times the
cell width, times the integer scale `s`) and, when the advance overruns
it, rasterizes at the size that makes it fit. This follows kitty, keyed
on the advance rather than the ink box.

The allowed overrun is `s` pixels, not a fixed one: the cell width
rounds the primary advance, so a primary glyph already overruns by up to
half a pixel times `s`, and a fixed pixel shrank sized ASCII from s=3.
A fixed symbol table (ghostty's `isSymbol`) was not taken because the
advance already identifies the glyphs that overrun, on whatever fallback
faces the host installs.

The fitting test runs on the pinned test font set, so CI exercises a
real fallback overrun instead of skipping on hosts without a CJK face.

Assisted-by: Claude Code

natsukium referenced this pull request 2026-10-01 12:50:21 +09:00

Decide on an ambiguous-width-as-wide setting #16

natsukium referenced this pull request 2026-10-01 12:50:30 +09:00

render: fit multi-codepoint clusters to their cells #17

natsukium changed title from Shrink a glyph that a fallback face draws wider than its cells to Fit a glyph that a fallback face draws wider than its cells 2026-10-02 22:14:17 +09:00

natsukium force-pushed fix/fit-overwide-glyphs from 5e89f771fc to 7a7ea401ef 2026-10-02 22:14:17 +09:00 Compare

natsukium force-pushed fix/fit-overwide-glyphs from 7a7ea401ef to eb346f34d0 2026-10-03 00:54:43 +09:00 Compare

natsukium force-pushed fix/fit-overwide-glyphs from eb346f34d0 to fc37243bd5 2026-10-03 00:56:27 +09:00 Compare

natsukium merged commit 41b169e851 into main 2026-10-03 11:50:52 +09:00

natsukium deleted branch fix/fit-overwide-glyphs 2026-10-03 11:50:52 +09:00

natsukium referenced this pull request from a commit 2026-10-03 11:50:53 +09:00

Merge pull request 'Fit a glyph that a fallback face draws wider than its cells' (#10) from fix/fit-overwide-glyphs into main

natsukium referenced this pull request 2026-10-06 11:45:34 +09:00

Decide on an ambiguous-width-as-wide setting #16

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