Release 0.33.0 - egui::Plugin, better kerning, kitdiff viewer

[lucasmerlin]

Short bluesky announcement:

We just released egui 0.33.0!

Highlights:

• egui::Plugin a improved way to create and access egui plugins
• kitdiff, a viewer for egui_kittest image snapshots (and a general image diff tool)
• better kerning (check the diff on kitdiff)

Screen.Recording.2025-10-09.at.13.43.19.mp4

Relaese Changelog:

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, a startup building an SDK for visualizing streams of multimodal data.

egui 0.33.0 changelog

Highlights from this release:

• egui::Plugin a improved way to create and access egui plugins
• kitdiff, a viewer for egui_kittest image snapshots (and a general image diff tool)
• better kerning

Improved kerning

As a step towards using 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:

egui::Plugin trait

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.

kitdiff, a image diff viewer

At rerun we have a ton of snapshots. Some PRs will change most of them (e.g. the one 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.
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):

Screen.Recording.2025-10-09.at.13.43.19.mp4

Migration guide

• 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.)

[github-actions]

Preview available at https://egui-pr-preview.github.io/pr/7622-release-0330
Note that it might take a couple seconds for the update to show up after the preview_build workflow has completed.

View snapshot changes at kitdiff