Fixes#8079, where font hinting only sharpens the vertical axis
(vertical stems stay blurry), and none of the skrifa knobs were
reachable — only switching to `Target::Mono` helped, but that wasn't
exposed.
This makes the hinting target configurable instead of hardcoding
`Target::Smooth { symmetric_rendering: true, preserve_linear_metrics:
true }`.
### API
- New `epaint::text::HintingTarget` mirroring `skrifa::outline::Target`:
- `Mono`
- `Smooth(SmoothHinting)` where `SmoothHinting { light,
symmetric_rendering, preserve_linear_metrics }`
- New field `FontTweak::hinting_target: HintingTarget`.
- Each variant/field is documented with what it does and the
egui-specific caveats (e.g. `symmetric_rendering` only affects
interpreter-hinted fonts; egui positions glyphs from shaper advances so
`preserve_linear_metrics` mostly affects sharpness, not layout).
### Render
- `font.rs` converts `HintingTarget` → `skrifa::outline::Target` and
threads it into the per-glyph `reconfigure` call; the hinting instance
is also reconfigured when the target changes.
### UI
- The font-tweak settings panel gets a `hinting_target` row: Smooth/Mono
radios, `light` / `symmetric_rendering` / `preserve_linear_metrics`
checkboxes, and a `Reset` button — all with tooltips.
### Behavior
- `HintingTarget::default()` matches egui's previous hardcoded target,
so **rendering is unchanged** unless you opt in. To fix the horizontal
blur from #8079, uncheck `preserve_linear_metrics` (or pick `Mono`).
Whether to flip the *default* is left as a follow-up.
🤖 Generated with [Claude Code](https://claude.com/claude-code)
---------
Co-authored-by: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
`ab_glyph` would output coverage values, but `vello` outputs RGBA. So
the old name was a misnomer.
I also suspect our default values are wrong, but I need to investigate
that more properly in a separate PR.
This lets you turn off subpixel horizontal binning of glyphs. The option
is a trade-off between even kerning and sharp text.
* Closes https://github.com/emilk/egui/issues/8034
* Related to #56 (Improve text — tracking issue)
## Summary
This PR integrates [harfrust](https://crates.io/crates/harfrust) (a
pure-Rust port of HarfBuzz) into epaint's text layout pipeline,
replacing the character-by-character glyph positioning with proper
OpenType text shaping.
### What this enables
- **GPOS kerning**: most modern fonts only ship kerning in GPOS tables
(not the legacy `kern` table). Pairs like "AV", "VA", "AT" are now
properly tightened.
- **GSUB substitutions**: ligatures (fi, fl), contextual alternates, and
other OpenType features.
- **Combining marks**: diacritics (e.g. ɔ̃) are positioned via anchor
tables instead of being rendered as standalone replacement glyphs.
### Before/After
#### Kerning, etc.
<img width="838" height="726" alt="before_main"
src="https://github.com/user-attachments/assets/f0f26d5f-b117-43a6-b39c-ea40d2e73836"
/>
<img width="838" height="726" alt="after_harfrust"
src="https://github.com/user-attachments/assets/d983e5da-486c-4f39-bd4f-5782a90c6b39"
/>
#### Ligatures
<img width="1117" height="698" alt="before_closeup"
src="https://github.com/user-attachments/assets/7a3b08b4-cf6f-45b7-98ba-07c473cd3b02"
/>
<img width="1117" height="698" alt="after_closeup"
src="https://github.com/user-attachments/assets/6cfc5f21-d32f-4f09-be0c-59c8c553d44f"
/>
### Architecture
The shaping integrates into the existing pipeline without changing the
public API:
1. **`Font::segment_into_runs`** — segments text into contiguous runs by
font face (grapheme-cluster aware, never splits combining sequences)
2. **`FontFace::shape_text`** — calls harfrust to shape each run,
returning glyph IDs + positioned advances/offsets
3. **`layout_shaped_run`** — emits `Glyph` structs from the shaping
output, with NOTDEF fallback to other font faces for missing glyphs
4. **Buffer recycling** — `FontsImpl` pools a `harfrust::UnicodeBuffer`
to avoid per-layout allocations
### Disclaimer
I'm far from being a good Rust programmer. Claude Code did most of the
heavy lifting here. I did my best and used my limited knowledge to avoid
making too many mistakes. If this PR isn't up to quality standards,
please don't hesitate to close it.
## Test plan
- [x] `cargo test -p epaint` — all 18 text tests pass, including 6 new
ones
- [x] `cargo clippy -p epaint --all-features` — clean
- [x] `cargo fmt` — clean
- [ ] Snapshot tests need regeneration (expected: shaping changes glyph
positions)
- New tests added:
- `test_gpos_kerning` — verifies GPOS kerning tightens "AV", "VA", "AT"
pairs
- `test_combining_diacritics` — combining tilde doesn't add extra width
- `test_shaping_basic_latin` — sanity check for Latin text
- `test_shaping_empty_string` — empty input doesn't panic
- `test_shaping_multiple_newlines` — newline splitting works correctly
- `test_shaping_mixed_font_fallback` — Latin + emoji in same string
---------
Co-authored-by: Emil Ernerfeldt <emil.ernerfeldt@gmail.com>
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* Closes N/A
* [x] I have followed the instructions in the PR template
This was mostly from last month, but I never got around to submitting
it.
This PR adds font variation coordinates to the `TextFormat` struct, and
uses them when rendering text. The coordinates are stored in a
`SmallVec`; I've chosen to store up to 2 inline, which makes it take up
24 bytes (the minimum possible for a `SmallVec`). The variation axis
tags are stored as the `font_types::Tag` type, which I've chosen to
re-export from `epaint::text`.
The variation coordinates are resolved to a `skrifa::Location` during
font rendering/scaling, and are cached in the same way as all the other
scaled metrics. I've renamed the `ScaledMetrics` struct to
`StyledMetrics`, since it now also contains the resolved variation
coordinates. I haven't benchmarked the performance of text layout with
variation coordinates, but the existing text layout performance is
unchanged.
I've replaced the API for manually overriding a font's weight
(https://github.com/emilk/egui/pull/7790) with an API for manually
overriding any variation coordinates via `FontTweak`. This should
support the same use case as #7790 while being substantially more
flexible.
I have *not* yet added any higher-level API for mapping style attributes
(weight, width, slant, etc) to variation coordinates or to different
font faces within a single family. That's a pretty huge can of worms,
and it'd involve rethinking the split between `FontId` and `TextFormat`
(and whether `FontId` is so big that we should provide a way to reuse
it). This API is intentionally pretty low-level for now.
Likewise, I've intentionally not used variation coordinates when
computing a font's row height. I can't think of any fonts that change
their vertical metrics depending on variation axes, so this should be
fine for now.
---------
Co-authored-by: Emil Ernerfeldt <emil.ernerfeldt@gmail.com>
* Closes N/A
* [x] I have followed the instructions in the PR template
This appears to have snuck in as part of
https://github.com/emilk/egui/pull/7790, which claimed to only be a
bugfix but introduced a new `font_weight` method.
I believe there's no way to access the method from *public* code since
it's only defined on `FontsImpl`, not the public-facing `FontsView`.
It's also not used *privately* in epaint, meaning it's completely dead
code.
Even if we *do* want some sort of future API for getting a font's
weight, it requires more consideration. For instance, this API will
return the default weight for variable fonts, which is not documented
anywhere and might not be what we want.
Previously, when loading a variable font (e.g. via
`egui::FontData::from_static`),
the font was rendered using the default (often the lightest) weight,
ignoring any preferred weight configuration.
This change applies the specified weight to skrifa's `Location` for the
`wght` axis,
ensuring that variable fonts are rendered with the intended font weight.
## Summary
Fixes variable font weight not being applied during rendering. The
`FontData::weight()` method now properly configures the font variation
axis.
## Changes
- Add `location: Location` field to `FontFace` to store variation
coordinates
- Pass `location` parameter through to glyph rendering functions
- Apply weight to skrifa's `LocationRef` in `DrawSettings` and
`HintingInstance`
## Weight Priority
1. `preferred_weight` from `FontData::weight()`
2. OS/2 table's `us_weight_class`
3. Variable font's fvar default value
4. `Location::default()`
## Related Issue
- #3218 : Not follow font id, but goal would be same
## Todo
* [x] Apply preferred font weight when loading variable fonts
* [ ] Add small size variable fonts for docs and egui (need discussion)
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* Closes N/A
* [x] I have followed the instructions in the PR template
I'll probably come back to this and clean it up a bit. This PR
reimplements ab_glyph's functionality on top of Skrifa, a somewhat
lower-level font API that's being used in Chrome now.
Skrifa doesn't perform rasterization itself, so I'm using
[vello_cpu](https://github.com/linebender/vello) from the Linebender
project for rasterization. It's still in its early days, but I believe
it's already quite fast. It also supports color and gradient fills, so
color emoji support will be easier.
Skrifa also supports font hinting, which should make text look a bit
nicer / less blurry.
Here's the current ab_glyph rendering:
<img width="1592" height="1068" alt="image"
src="https://github.com/user-attachments/assets/2385b66e-23f8-4c6e-b8c2-ea90e0eea4e4"
/>
Here's Skrifa *without* hinting--it looks almost identical, but there
are some subpixel differences, probably due to rasterizer behavior:
<img width="1592" height="1068" alt="image"
src="https://github.com/user-attachments/assets/a815f3e9-65ac-4940-bc00-571177bef53d"
/>
Here's Skrifa *with* hinting:
<img width="1592" height="1068" alt="image"
src="https://github.com/user-attachments/assets/d6cc0669-3537-4377-bba9-ed5ef09664db"
/>
Hinting does make the horizontal strokes look a bit bolder, which makes
me wonder once again about increasing the font weight from "light" to
"regular".
---------
Co-authored-by: Emil Ernerfeldt <emil.ernerfeldt@gmail.com>
* [x] I have followed the instructions in the PR template
Splitting this out from the Parley work as requested. This removes
`FontImage` and makes the font atlas use a `ColorImage`. It converts
alpha to coverage at glyph-drawing time, not at delta-upload time.
This doesn't do much now, but will allow for color emoji rendering once
we start using Parley.
I've changed things around so that we pass in `text_alpha_to_coverage`
to the `Fonts` the same way we do with `pixels_per_point` and
`max_texture_side`, reusing the existing code to check if the setting
differs and recreating the font atlas if so. I'm not quite sure why this
wasn't done in the first place.
I've left `ImageData` as an enum for now, in case we want to add support
for more texture pixel formats in the future (which I personally think
would be worthwhile). If you'd like, I can just remove that enum
entirely.
Enabled the `missing_assert_message` lint
* [x] I have followed the instructions in the PR template
---------
Co-authored-by: Lucas Meurer <lucasmeurer96@gmail.com>
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I removed (I hope so) all wildcard imports I found.
For me on my pc this improved the build time:
- for egui -5s
- for eframe -12s
* [x] I have followed the instructions in the PR template
I wanted to implement a font picker that loads all system fonts but ran
into panics due to missing glyphs. Falling back to an empty glyph when
none of the fallback glyphs are available avoids the panic.
The ignored characters are used in some custom fonts.
for example: the \u{F0FF} is used as `cleaning_services` in
MaterialIcons-Regular.ttf
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Closes <https://github.com/emilk/egui/issues/THE_RELEVANT_ISSUE>.
---------
Co-authored-by: Emil Ernerfeldt <emil.ernerfeldt@gmail.com>
* eframe README: explain how to enable copy/paste
* Implement Debug for a couple of structs
* Code cleanup
* Better docs
* profile ron serialization
* CI: Allow "exclude from changelog" as the only label
* Add `TextFormat::extra_letter_spacing`
* Add control of line height
* Add to text layout demo
* Move the text layout demo to its own window in the demo app
* Fix doclink
* Better document points vs pixels
* Better documentation and code cleanup
* use font metrics in layout
* properly center scaled fonts
* adjust docs
* fix raised text
* fix easymark viewer small text alignment
caused by variable row heights
* eframe web: Add WebInfo::user_agent
* Deprecate `Modifier::ALT_SHIFT`
* Add code for formatting Modifiers and Key
* Add type KeyboardShortcut
* Code cleanup
* Add Context::os/set_os to query/set what OS egui believes it is on
* Add Fonts::has_glyph(s)
* Add helper function for formatting keyboard shortcuts
* Faster code
* Add way to set a shortcut text on menu buttons
* Cleanup
* format_keyboard_shortcut -> format_shortcut
* Add TODO about supporting more keyboard sumbols
* Modifiers::plus
* Use the new keyboard shortcuts in emark editor demo
* Explain why ALT+SHIFT is a bad modifier combo
* Fix doctest
