Release 0.33.0 - `egui::Plugin`, better kerning, kitdiff viewer (#7622)

We just released egui 0.33.0!

Highlights:
- `egui::Plugin` a improved way to create and access egui plugins
- [kitdiff](https://github.com/rerun-io/kitdiff), a viewer for
egui_kittest image snapshots (and a general image diff tool)
- better kerning (check the diff on
[kitdiff](https://rerun-io.github.io/kitdiff/?url=https://github.com/emilk/egui/pull/7431))

https://github.com/user-attachments/assets/971f0493-6dae-42e5-8019-58b74cf5d203

egui is an easy-to-use immediate mode GUI for Rust that runs on both web
and native.

Try it now: <https://www.egui.rs/>

egui development is sponsored by [Rerun](https://www.rerun.io/), a
startup building an SDK for visualizing streams of multimodal data.

Highlights from this release:
- `egui::Plugin` a improved way to create and access egui plugins
- [kitdiff](https://github.com/rerun-io/kitdiff), a viewer for
egui_kittest image snapshots (and a general image diff tool)
- better kerning

As a step towards using [parley](https://github.com/linebender/parley)
for font rendering, @valadaptive has refactored the font loading and
rendering code. A result of this (next to the font rendering code being
much nicer now) is improved kerning.
Notice how the c moved away from the k:

![Oct-09-2025
16-21-58](https://github.com/user-attachments/assets/d4a17e87-5e98-40db-a85a-fa77fa77aceb)

We've added a new trait-based plugin api, meant to replace
`Context::on_begin_pass` and `Context::on_end_pass`.
This makes it a lot easier to handle state in your plugins. Instead of
having to write to egui memory it can live right on your plugin struct.
The trait based api also makes easier to add new hooks that plugins can
use. In addition to `on_begin_pass` and `on_end_pass`, the `Plugin`
trait now has a `input_hook` and `output_hook` which you can use to
inspect / modify the `RawInput` / `FullOutput`.

At rerun we have a ton of snapshots. Some PRs will change most of them
(e.g. [the](https://github.com/rerun-io/rerun/pull/11253/files)
[one](https://rerun-io.github.io/kitdiff/?url=https://github.com/rerun-io/rerun/pull/11253/files)
that updated egui and introduced the kerning improvements, ~500
snapshots changed!).
If you really want to look at every changed snapshot it better be as
efficient as possible, and the experience on github, fiddeling with the
sliders, is kind of frustrating.
In order to fix this, we've made
[kitdiff](https://rerun-io.github.io/kitdiff/).
You can use it locally via
- `kitdiff files .` will search for .new.png and .diff.png files
- `kitdiff git` will compare the current files to the default branch
(main/master)
Or in the browser via
- going to https://rerun-io.github.io/kitdiff/ and pasting a PR or
github artifact url
- linking to kitdiff via e.g. a github workflow
`https://rerun-io.github.io/kitdiff/?url=<link_to_pr_or_artefact>`

To install kitdiff run `cargo install --git
https://github.com/rerun-io/kitdiff`

Here is a video showing the kerning changes in kitdiff ([try it
yourself](https://rerun-io.github.io/kitdiff/?url=https://github.com/rerun-io/rerun/pull/11253/files)):

https://github.com/user-attachments/assets/74640af1-09ba-435a-9d0c-2cbeee140c8f

- `egui::Mutex` now has a timeout as a simple deadlock detection
- If you use a `egui::Mutex` in some place where it's held for longer
than a single frame, you should switch to the std mutex or parking_lot
instead (egui mutexes are wrappers around parking lot)
- `screen_rect` is deprecated
- In order to support safe areas, egui now has `viewport_rect` and
`content_rect`.
- Update all usages of `screen_rect` to `content_rect`, unless you are
sure that you want to draw outside the `safe area` (which would mean
your Ui may be covered by notches, system ui, etc.)

CHANGELOG.md

@@ -14,7 +14,7 @@ This file is updated upon each release.
 Changes since the last release can be found at <https://github.com/emilk/egui/compare/latest...HEAD> or by running the `scripts/generate_changelog.py` script.
 
 
-## 0.33.0 - 2025-10-09
+## 0.33.0 - 2025-10-09 - `egui::Plugin`, better kerning, kitdiff viewer
 Highlights from this release:
 - `egui::Plugin` a improved way to create and access egui plugins
 - [kitdiff](https://github.com/rerun-io/kitdiff), a viewer for egui_kittest image snapshots (and a general image diff tool)