* Fixes https://github.com/rerun-io/rerun/issues/6638
* Related? https://github.com/emilk/egui/issues/4563
This improves how an eframe canvas works inside of a larger web page,
and how it works when there are multiple eframe apps in the same page.
`eframe` will set `tabindex="0"` on the canvas automatically, making it
focusable.
It will also set `outline: none` on the CSS, so the focused canvas won't
have an ugly outline.
## Breaking changes
You may wanna add this to your `index.html` to give the canvas focus on
startup:
```js
document.getElementById("the_canvas_id").focus();
```
## Test setup
```sh
./scripts/build_demo_web.sh
./scripts/start_server.sh
open http://localhost:8888/multiple_apps.html
```
Then open the "Input Event History" and "Text Edit" windows
## Tested
* Chromium
* [x] drag-and-drop of files
* Test both when a `TextEdit` is focused and when it is not:
* [x] `Event::Key`
* [x] `Event::Text`
* [x] copy-cut-paste
* [x] Wheel scroll
* [x] `Event::PointerGone`
* [x] Mouse drag
* [x] Mouse click
* [x] Mouse right-click
* [x] Defocus all eframe canvas, and then start typing text
* [x] Firefox (all of the above)
* [x] Desktop Safari (all of the above)
* [x] Mobile Safari
## Future work (pre-existing issues)
* https://github.com/emilk/egui/issues/4723
* https://github.com/emilk/egui/issues/4724
* https://github.com/emilk/egui/issues/4725
* https://github.com/emilk/egui/issues/4726
Currently, if the size of the canvas element changes independently of
the size of the browser window (e.g. due to its parent element
shrinking), then no repaints are scheduled.
This PR replaces the `resize` event with a `ResizeObserver`, which
ensures that _any_ resize of the canvas element (including those caused
by browser window resizes) trigger a repaint. The repaint is done
synchronously as part of the resize event, to reduce any potential
flickering.
The result seems to pass the rendering tests on most platform+browser
combinations. We tested:
- Chrome, Firefox, Safari on macOS
- Chrome, Firefox on Linux (ubuntu and arch, both running wayland)
- Chrome, Firefox on Windows
Firefox still has some antialiasing issues on Linux platforms, but this
antialiasing also happens on `master`, so this PR is not a regression
there.
The code setting `canvas.style.width` and `canvas.style.height` at the
start of `AppRunner::logic` was also removed - the canvas _display_ size
is now fully controlled by CSS, e.g. by setting `canvas { width: 100%;
height: 100%; }`.
The approach used here is described in
https://webglfundamentals.org/webgl/lessons/webgl-resizing-the-canvas.html
Note: The only remaining place where egui updates the style of the
canvas it is rendering to is some of the IME/mobile input handling code.
Fixing that is out of scope for this PR, and will be done in a followup
PR.
* Closes https://github.com/emilk/egui/issues/4241
I would love some more testers of this.
I'm not sure if we really need the round-to-even code, but I'm hesitant
to out-right revert https://github.com/emilk/egui/pull/151 when I cannot
reproduce its problem. Keeping it seems quite safe though.
---
# Testing
Checkout the branch and run:
* `./scripts/start_server.sh`
* `./scripts/build_demo_web.sh` and then open
`http://localhost:8888/index.html#Rendering`
* `./scripts/build_demo_web.sh --wgpu` and then open
`http://localhost:8888/index.html#Rendering`
Check the "Rendering test" that the squares in the pixel alignment test
are perfectly sharp, like this:
<img width="576" alt="Screenshot 2024-04-01 at 13 27 20"
src="https://github.com/emilk/egui/assets/1148717/fb6c4824-9e25-4304-bc0c-3c50fbd44a52">
If it looks something like this, something is WRONG:
<img width="488" alt="Screenshot 2024-04-01 at 13 29 07"
src="https://github.com/emilk/egui/assets/1148717/04bd93ff-2108-40c5-95f6-76e3bcb9cd7f">
Please try it on different zoom levels in different browsers, and if
possible on different monitors with different native dpi scaling. Report
back the results!
### Mac
I have tested on a high-DPI Mac:
* Chromium (Brave): ✅ Can reproduce problem on `master`, and it's now
fixed
* Firefox: ✅ Can reproduce problem on `master`, and it's now fixed
* Safari: ❌ Can't get it to work; giving up for now
Emil Ernerfeldt