* part of #7264
* based on https://github.com/emilk/egui/pull/8152
The resize fix allows use to really simplify how the Window Titlebar is
rendered. Previously it was using some complex flow to calculate and
allocate the height first and then render it later once we knew the
windows final width.
Since now windows can't shrink past their minimum content widths, I can
just show the titlebar inline with the regular content, just outside of
the `Resize` container so that it is always visible.
This does change what the size of a window means. Before, size was just
the size of the contents, while now size (e.g. via min_height) will
include the Frames margin and outline, title bar and the contents.
Also, the window label now truncates as you shrink the window (meaning
windows can now be smaller than their label allows).
---------
Co-authored-by: lucasmerlin <8009393+lucasmerlin@users.noreply.github.com>
* 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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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>
Sometimes when moving a window, having a tooltip attached to the mouse
pointer, or scrolling a `ScrollArea`, you would see this disturbing
effect:
This is caused by us rounding many visual elements (lines, rectangles,
text, …) to physical pixels in order to keep them sharp. If the
window/tooltip itself is not rounded to a physical pixel, then you can
get this behavior.
So from now on the position of all
areas/windows/tooltips/popups/ScrollArea gets rounded to the closes
pixel.
* Unlocked by https://github.com/emilk/egui/pull/7709
This adds a new mode, `UPDATE_SNAPSHOTS=force`, which will lower the
threshold to zero, overwriting every image that is not _exactly_ the
same.
Most comparisons has a threshold because different GPUs render slightly
differently. However, setting that threshold accurately can be hard.
Sometimes a test will pass locally, but fail on CI. In those cases you
want to force an update of the failing test. You can use
`UPDATE_SNAPSHOTS=force` for that.
And sometimes a small change _should_ update all images, but the change
is so tiny that it falls under the threshold. Still, you want to make a
point of showing that these images have changes. You can use
`UPDATE_SNAPSHOTS=force` for that.
