bevy/examples/ui/window_fallthrough.rs
Jan Hohenheim a750cfe4a1
Split CursorOptions off of Window (#19668)
# Objective

- Fixes #19627 
- Tackles part of #19644 
- Supersedes #19629
- `Window` has become a very very very big component
- As such, our change detection does not *really* work on it, as e.g.
moving the mouse will cause a change for the entire window
- We circumvented this with a cache
- But, some things *shouldn't* be cached as they can be changed from
outside the user's control, notably the cursor grab mode on web
- So, we need to disable the cache for that
- But because change detection is broken, that would result in the
cursor grab mode being set every frame the mouse is moved
- That is usually *not* what a dev wants, as it forces the cursor to be
locked even when the end-user is trying to free the cursor on the
browser
  - the cache in this situation is invalid due to #8949

## Solution

- Split `Window` into multiple components, each with working change
detection
- Disable caching of the cursor grab mode
- This will only attempt to force the grab mode when the `CursorOptions`
were touched by the user, which is *much* rarer than simply moving the
mouse.
- If this PR is merged, I'll do the exact same for the other
constituents of `Window` as a follow-up

## Testing

- Ran all the changed examples
2025-06-17 20:20:13 +00:00

55 lines
2.1 KiB
Rust

//! This example illustrates how have a mouse's clicks/wheel/movement etc fall through the spawned transparent window to a window below.
//! If you build this, and hit 'P' it should toggle on/off the mouse's passthrough.
//! Note: this example will not work on following platforms: iOS / Android / Web / X11. Window fall through is not supported there.
use bevy::{prelude::*, window::CursorOptions};
fn main() {
App::new()
.insert_resource(ClearColor(Color::NONE)) // Use a transparent window, to make effects obvious.
.add_plugins(DefaultPlugins.set(WindowPlugin {
primary_window: Some(Window {
// Set the window's parameters, note we're setting the window to always be on top.
transparent: true,
decorations: true,
window_level: bevy::window::WindowLevel::AlwaysOnTop,
..default()
}),
..default()
}))
.add_systems(Startup, setup)
.add_systems(Update, toggle_mouse_passthrough) // This allows us to hit 'P' to toggle on/off the mouse's passthrough
.run();
}
fn setup(mut commands: Commands, asset_server: Res<AssetServer>) {
// UI camera
commands.spawn(Camera2d);
// Text with one span
commands.spawn((
// Accepts a `String` or any type that converts into a `String`, such as `&str`
Text::new("Hit 'P' then scroll/click around!"),
TextFont {
font: asset_server.load("fonts/FiraSans-Bold.ttf"),
font_size: 83.0, // Nice and big so you can see it!
..default()
},
// Set the style of the TextBundle itself.
Node {
position_type: PositionType::Absolute,
bottom: Val::Px(5.),
right: Val::Px(10.),
..default()
},
));
}
// A simple system to handle some keyboard input and toggle on/off the hit test.
fn toggle_mouse_passthrough(
keyboard_input: Res<ButtonInput<KeyCode>>,
mut cursor_options: Single<&mut CursorOptions>,
) {
if keyboard_input.just_pressed(KeyCode::KeyP) {
cursor_options.hit_test = !cursor_options.hit_test;
}
}