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# What it does
Addition of a new system of theme plugins which allow the user to use
different rules engine to compute the style for the available
specialised widget style.
# How to use
Create a engine implementing the trait `ThemePlugin` and `ThemeStyle<S:
StyleStruct>` and implement the necessary methods, then register this
way (example for `ButtonStyle`):
```ui.add_theme::<ButtonStyle>(&mycustomengine);```
Now all button will call the `ThemeStyle<ButtonStyle>` method to compute the correct style and later use the cached value to avoid the costly computation.
If no valid `ThemeStyle<S>` or engine is available then it fallback to the default style.
* Closes part of <https://github.com/emilk/egui/issues/3284>
* [x] I have followed the instructions in the PR template
---------
Co-authored-by: adrien <221212@umons.ac.be>
Co-authored-by: Emil Ernerfeldt <emil.ernerfeldt@gmail.com>
Co-authored-by: Claude Opus 5 (1M context) <noreply@anthropic.com>
Co-authored-by: Lucas Meurer <hi@lucasmerlin.me>
* 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>
- fix for https://github.com/rerun-io/reality/pull/1075
The galleys row size was calculated by looking at the last glyphs pos_x,
which got changed to be rounded to integers when we added subpixel
binning. This introduced a subtle bug which caused the width of galleys
to be slightly off.
This PR fixes this by looking at the actual cursor position instead,
which is not rounded.
Also added a test to ensure this is correct. Previously, for the second
and last line, the `x` was too close to the `0`.
<img width="48" height="67" alt="image"
src="https://github.com/user-attachments/assets/a69a4cc3-b3f3-4553-ab92-73cb2e7a358c"
/>
---------
Co-authored-by: lucasmerlin <8009393+lucasmerlin@users.noreply.github.com>
<!--
Please read the "Making a PR" section of
[`CONTRIBUTING.md`](https://github.com/emilk/egui/blob/main/CONTRIBUTING.md)
before opening a Pull Request!
* Keep your PR:s small and focused.
* The PR title is what ends up in the changelog, so make it descriptive!
* If applicable, add a screenshot or gif.
* If it is a non-trivial addition, consider adding a demo for it to
`egui_demo_lib`, or a new example.
* Do NOT open PR:s from your `master` branch, as that makes it hard for
maintainers to test and add commits to your PR.
* Remember to run `cargo fmt` and `cargo clippy`.
* Open the PR as a draft until you have self-reviewed it and run
`./scripts/check.sh`.
* When you have addressed a PR comment, mark it as resolved.
Please be patient! I will review your PR, but my time is limited!
-->
* 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>
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.
## Defining what `Rounding` is
This PR defines what `Rounding` means: it is the corner radius of
underlying `RectShape` rectangle. If you use `StrokeKind::Inside`, this
means the rounding is of the outer part of the stroke. Conversely, if
you use `StrokeKind::Outside`, the stroke is outside the rounded
rectangle, so the stroke has an inner radius or `rounding`, and an outer
radius that is larger by `stroke.width`.
This definitions is the same as Figma uses.
## Improving general shape rendering
The rendering of filled shapes (rectangles, circles, paths, bezier) has
been rewritten. Instead of first painting the fill with the stroke on
top, we now paint them as one single mesh with shared vertices at the
border. This has several benefits:
* Less work (faster and with fewer vertices produced)
* No overdraw (nicer rendering of translucent shapes)
* Correct blending of stroke and fill
The logic for rendering thin strokes has also been improved, so that the
width of a stroke of `StrokeKind::Outside` never affects the filled area
(this used to be wrong for thin strokes).
## Improving of rectangle rendering
Rectangles also has specific improvements in how thin rectangles are
painted.
The handling of "Blur width" is also a lot better, and now works for
rectangles with strokes.
There also used to be bugs with specific combinations of corner radius
and stroke width, that are now fixed.
## But why?
With the new `egui::Scene` we end up with a lot of zoomed out shapes,
with sub-pixel strokes. These need to look good! One thing led to
another, and then I became obsessive 😅
## Tessellation Test
In order to investigate the rendering, I created a Tessellation Test in
the `egui_demo_lib`.
[Try it
here](https://egui-pr-preview.github.io/pr/5669-emilkimprove-tessellator)
Previously, `Harness::run` just called `Harness::step` 3 times. If that
wasn't enough, tests would often call run multiple times so all
animations would finish properly.
Also, I introduced `HarnessBuilder::with_step_dt` to customize with how
big of a dt each frame is called. I set the default to 1.0 / 6.0 (~6fps)
so we don't waste cpu in tests waiting on animations.
`HarnessBuilder::max_steps` allows us to control how many steps
`Harness::run` should run before panicing.
The default is 6, so we run for up to 1.0 logical seconds (six frames at
6 fps), which should be enough to finish most animations.
Turns out a lot of snapshots where rendered before fully shown and had a
light opacity, those are now fixed.
* [x] I have followed the instructions in the PR template
* Part of https://github.com/emilk/egui/issues/4019
`Frame` now includes the width of the stroke as part of its size. From
the new docs:
### `Frame` docs
The total (outer) size of a frame is `content_size + inner_margin +
2*stroke.width + outer_margin`.
Everything within the stroke is filled with the fill color (if any).
```text
+-----------------^-------------------------------------- -+
| | outer_margin |
| +------------v----^------------------------------+ |
| | | stroke width | |
| | +------------v---^---------------------+ | |
| | | | inner_margin | | |
| | | +-----------v----------------+ | | |
| | | | ^ | | | |
| | | | | | | | |
| | | |<------ content_size ------>| | | |
| | | | | | | | |
| | | | v | | | |
| | | +------- content_rect -------+ | | |
| | | | | |
| | +-------------fill_rect ---------------+ | |
| | | |
| +----------------- widget_rect ------------------+ |
| |
+---------------------- outer_rect ------------------------+
```
The four rectangles, from inside to outside, are:
* `content_rect`: the rectangle that is made available to the inner
[`Ui`] or widget.
* `fill_rect`: the rectangle that is filled with the fill color (inside
the stroke, if any).
* `widget_rect`: is the interactive part of the widget (what sense
clicks etc).
* `outer_rect`: what is allocated in the outer [`Ui`], and is what is
returned by [`Response::rect`].
### Notes
This required rewriting a lot of the layout code for `egui::Window`,
which was a massive pain. But now the window margin and stroke width is
properly accounted for everywhere.
* Merge this first: https://github.com/emilk/egui/pull/5517
This aligns all rectangles and (horizontal or vertical) line segments to
the physical pixel grid in the `epaint::Tessellator`, making these
shapes appear crisp everywhere.
* Closes https://github.com/emilk/egui/issues/5164
* Closes https://github.com/emilk/egui/issues/3667
This undoes a lot of the explicit, egui-side aligning added in:
* https://github.com/emilk/egui/pull/4943
The new approach has several benefits over the old one:
* It is done automatically by epaint, so it is applied to everything (no
longer opt-in)
* It is applied after any layer transforms (so it always works)
* It makes line segments crisper on high-DPI screens
* All filled rectangles now has sides that end on pixel boundaries
- closes#3491
- closes#3926
This adds a testing library to egui based on
[kittest](https://github.com/rerun-io/kittest). Kittest is a new
[AccessKit](https://github.com/AccessKit/accesskit/)-based testing
library. The api is inspired by the js
[testing-library](https://testing-library.com/) where the idea is also
to query the dom based on accessibility attributes.
We made kittest with egui in mind but it should work with any rust gui
framework with AccessKit support.
It currently has support for:
- running the egui app, frame by frame
- building the AccessKit tree
- ergonomic queries via kittest
- via e.g. get_by_name, get_by_role
- simulating events based on the accesskit node id
- creating arbitrary events based on Harness::input_mut
- rendering screenshots via wgpu
- snapshot tests with these screenshots
A simple test looks like this:
```rust
fn main() {
let mut checked = false;
let app = |ctx: &Context| {
CentralPanel::default().show(ctx, |ui| {
ui.checkbox(&mut checked, "Check me!");
});
};
let mut harness = Harness::builder().with_size(egui::Vec2::new(200.0, 100.0)).build(app);
let checkbox = harness.get_by_name("Check me!");
assert_eq!(checkbox.toggled(), Some(Toggled::False));
checkbox.click();
harness.run();
let checkbox = harness.get_by_name("Check me!");
assert_eq!(checkbox.toggled(), Some(Toggled::True));
// You can even render the ui and do image snapshot tests
#[cfg(all(feature = "wgpu", feature = "snapshot"))]
egui_kittest::image_snapshot(&egui_kittest::wgpu::TestRenderer::new().render(&harness), "readme_example");
}
```
~Since getting wgpu to run in ci is a hassle, I'm taking another shot at
creating a software renderer for egui (ideally without a huge dependency
like skia)~ (this didn't work as well as I hoped and it turns out in CI
you can just run tests on a mac runner which comes with a real GPU)
Here is a example of a failed snapshot test in ci, it will say which
snapshot failed and upload an artifact with the before / after and diff
images:
https://github.com/emilk/egui/actions/runs/11183049487/job/31090724606?pr=5166
