This implements web support for taking screenshots in an eframe app (and
adds a nice demo).
It also updates the native screenshot implementation to work with the
wgpu gl backend.
The wgpu implementation is quite different than the native one because
we can't block to wait for the screenshot result, so instead I use a
channel to pass the result to a future frame asynchronously.
* Closes <https://github.com/emilk/egui/issues/5425>
* [x] I have followed the instructions in the PR template
https://github.com/user-attachments/assets/67cad40b-0384-431d-96a3-075cc3cb98fb
Previously, any frames in flight (`requestAnimationFrame`) on web were
not being cancelled (`cancelAnimationFrame`) when `WebRunner::destroy`
was called. If a user called `destroy`, then immediately removed the
canvas from the DOM, eframe could panic with a "failed to find (canvas)
element by id" error message.
This PR changes two things:
- The canvas element is directly referenced everywhere it's needed
instead of being looked up by `canvas_id`[^1]
- The RAF handle is stored in `WebRunner` and `cancelAnimationFrame` is
called on it inside of `WebRunner::destroy`[^2]
[^1]: The WebGL/WGPU backends were already holding onto the canvas (and
associated GPU context), so the change is just converting all the
`get_element_by_id` lookups to retrieve the canvas from the web runner
handle.
[^2]: There is only ever one frame in flight, so we store it directly as
a scalar field.
* Clear color values are not explicitely sent to the rendering backend as-is.
Previously, converting from Color32 to Rgba caused an srgb->linear conversion. This conversion is incorrect if the backbuffer doesn't perform automatic conversion from linear->srgb (lack of this conversion is generally what egui assumes!).
* fill in pr numbers in changelog
* Epi comment fix
Co-authored-by: Emil Ernerfeldt <emil.ernerfeldt@gmail.com>
* Color32 comment fix
Co-authored-by: Emil Ernerfeldt <emil.ernerfeldt@gmail.com>
* move changelog line
* rename fix
* use backticks in doc
---------
Co-authored-by: Emil Ernerfeldt <emil.ernerfeldt@gmail.com>
* basic working wgpu @ webgl on websys
* fix glow compile error
* introduced WebPainter trait, provide wgpu renderstate
* WebPainterWgpu destroy implemented
* make custom3d demo work on wgpu backend
* changelog entry for wgpu support eframe wasm
* remove temporary logging hack
* stop using pollster for web
we're actually not allowed to block - this only worked because wgpu on webgl doesn't actually cause anything blocking. However, when trying webgpu this became an issue
* revert cargo update
* compile error if neither glow nor wgpu features are enabled
* code cleanup
* Error handling
* Update changelog with link
* Make sure --all-features work
* Select best framebuffer format from the available ones
* update to wasm-bindgen 0.2.83
* Fix typo
* Clean up Cargo.toml
* Log about using the wgpu painter
* fixup wgpu labels
* fix custom3d_wgpu_shader ub padding
* remove duplicated uniforms struct in wgsl shader for custom3d
* Update docs: add async/await to the web 'start' function
Co-authored-by: Emil Ernerfeldt <emil.ernerfeldt@gmail.com>
