# Objective
Defocusing a window while a key is held (such as when Alt+tabbing), will
currently send a key release on X11 and Windows. This is likely the
behavior that most people expect.
However it's synthetic events from winit are unimplemented for WASM and
some other platforms. (See
https://github.com/rust-windowing/winit/issues/1272).
While we can implement it upstream, there is also some doubt about the
synthetic events API as a whole
(https://github.com/rust-windowing/winit/issues/3543), so I propose to
do it in bevy directly for now.
## Solution
This PR implements key tracking in bevy directly so we can synthesize
our own key release events across all platforms.
Note regarding X11 specifically:
- On `main`, pressing a keyboard shortcut to unfocus the window (`Ctrl +
Super + ArrowRight` in my case) will yield the following events:
```
Pressed Control
Pressed Super
Released Control
Released ArrowRight
Released Super
```
- On this branch, it will yield the following sequence:
```
Pressed Control
Pressed Super
Released Control
Released Super
```
To me the behavior of this branch is more expected than `main`, because
`main` produces an `ArrowRight` release without producing a press first.
## Testing
Tested in WASM and X11 with
```rust
App::new()
.add_plugins(DefaultPlugins)
.add_systems(Update, |mut keys: EventReader<KeyboardInput>| {
for ev in keys.read() {
error!("received {ev:?}");
}
})
.run();
```
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