Redo of #7590 since I messed up my branch.
# Objective
- Revise docs.
- Refactor event loop code a little bit to make it easier to follow.
## Solution
- Do the above.
---
### Migration Guide
- `UpdateMode::Reactive { max_wait: .. }` -> `UpdateMode::Reactive {
wait: .. }`
- `UpdateMode::ReactiveLowPower { max_wait: .. }` ->
`UpdateMode::ReactiveLowPower { wait: .. }`
---------
Co-authored-by: Sélène Amanita <134181069+Selene-Amanita@users.noreply.github.com>
Links in the api docs are nice. I noticed that there were several places
where structs / functions and other things were referenced in the docs,
but weren't linked. I added the links where possible / logical.
---------
Co-authored-by: Alice Cecile <alice.i.cecile@gmail.com>
Co-authored-by: François <mockersf@gmail.com>
# Objective
See:
- https://github.com/bevyengine/bevy/issues/7067#issuecomment-1381982285
- (This does not fully close that issue in my opinion.)
- https://discord.com/channels/691052431525675048/1063454009769340989
## Solution
This merge request adds documentation:
1. Alert users to the fact that `App::run()` might never return and code placed after it might never be executed.
2. Makes `winit::WinitSettings::return_from_run` discoverable.
3. Better explains why `winit::WinitSettings::return_from_run` is discouraged and better links to up-stream docs. on that topic.
4. Adds notes to the `app/return_after_run.rs` example which otherwise promotes a feature that carries caveats.
Furthermore, w.r.t `winit::WinitSettings::return_from_run`:
- Broken links to `winit` docs are fixed.
- Links now point to BOTH `EventLoop::run()` and `EventLoopExtRunReturn::run_return()` which are the salient up-stream pages and make more sense, taken together.
- Collateral damage: "Supported platforms" heading; disambiguation of "run" → `App::run()`; links.
## Future Work
I deliberately structured the "`run()` might not return" section under `App::run()` to allow for alternative patterns (e.g. `AppExit` event, `WindowClosed` event) to be listed or mentioned, beneath it, in the future.
*This PR description is an edited copy of #5007, written by @alice-i-cecile.*
# Objective
Follow-up to https://github.com/bevyengine/bevy/pull/2254. The `Resource` trait currently has a blanket implementation for all types that meet its bounds.
While ergonomic, this results in several drawbacks:
* it is possible to make confusing, silent mistakes such as inserting a function pointer (Foo) rather than a value (Foo::Bar) as a resource
* it is challenging to discover if a type is intended to be used as a resource
* we cannot later add customization options (see the [RFC](https://github.com/bevyengine/rfcs/blob/main/rfcs/27-derive-component.md) for the equivalent choice for Component).
* dependencies can use the same Rust type as a resource in invisibly conflicting ways
* raw Rust types used as resources cannot preserve privacy appropriately, as anyone able to access that type can read and write to internal values
* we cannot capture a definitive list of possible resources to display to users in an editor
## Notes to reviewers
* Review this commit-by-commit; there's effectively no back-tracking and there's a lot of churn in some of these commits.
*ira: My commits are not as well organized :')*
* I've relaxed the bound on Local to Send + Sync + 'static: I don't think these concerns apply there, so this can keep things simple. Storing e.g. a u32 in a Local is fine, because there's a variable name attached explaining what it does.
* I think this is a bad place for the Resource trait to live, but I've left it in place to make reviewing easier. IMO that's best tackled with https://github.com/bevyengine/bevy/issues/4981.
## Changelog
`Resource` is no longer automatically implemented for all matching types. Instead, use the new `#[derive(Resource)]` macro.
## Migration Guide
Add `#[derive(Resource)]` to all types you are using as a resource.
If you are using a third party type as a resource, wrap it in a tuple struct to bypass orphan rules. Consider deriving `Deref` and `DerefMut` to improve ergonomics.
`ClearColor` no longer implements `Component`. Using `ClearColor` as a component in 0.8 did nothing.
Use the `ClearColorConfig` in the `Camera3d` and `Camera2d` components instead.
Co-authored-by: Alice <alice.i.cecile@gmail.com>
Co-authored-by: Alice Cecile <alice.i.cecile@gmail.com>
Co-authored-by: devil-ira <justthecooldude@gmail.com>
Co-authored-by: Carter Anderson <mcanders1@gmail.com>
# Objective
- Reduce power usage for games when not focused.
- Reduce power usage to ~0 when a desktop application is minimized (opt-in).
- Reduce power usage when focused, only updating on a `winit` event, or the user sends a redraw request. (opt-in)
https://user-images.githubusercontent.com/2632925/156904387-ec47d7de-7f06-4c6f-8aaf-1e952c1153a2.mp4
Note resource usage in the Task Manager in the above video.
## Solution
- Added a type `UpdateMode` that allows users to specify how the winit event loop is updated, without exposing winit types.
- Added two fields to `WinitConfig`, both with the `UpdateMode` type. One configures how the application updates when focused, and the other configures how the application behaves when it is not focused. Users can modify this resource manually to set the type of event loop control flow they want.
- For convenience, two functions were added to `WinitConfig`, that provide reasonable presets: `game()` (default) and `desktop_app()`.
- The `game()` preset, which is used by default, is unchanged from current behavior with one exception: when the app is out of focus the app updates at a minimum of 10fps, or every time a winit event is received. This has a huge positive impact on power use and responsiveness on my machine, which will otherwise continue running the app at many hundreds of fps when out of focus or minimized.
- The `desktop_app()` preset is fully reactive, only updating when user input (winit event) is supplied or a `RedrawRequest` event is sent. When the app is out of focus, it only updates on `Window` events - i.e. any winit event that directly interacts with the window. What this means in practice is that the app uses *zero* resources when minimized or not interacted with, but still updates fluidly when the app is out of focus and the user mouses over the application.
- Added a `RedrawRequest` event so users can force an update even if there are no events. This is useful in an application when you want to, say, run an animation even when the user isn't providing input.
- Added an example `low_power` to demonstrate these changes
## Usage
Configuring the event loop:
```rs
use bevy::winit::{WinitConfig};
// ...
.insert_resource(WinitConfig::desktop_app()) // preset
// or
.insert_resource(WinitConfig::game()) // preset
// or
.insert_resource(WinitConfig{ .. }) // manual
```
Requesting a redraw:
```rs
use bevy:🪟:RequestRedraw;
// ...
fn request_redraw(mut event: EventWriter<RequestRedraw>) {
event.send(RequestRedraw);
}
```
## Other details
- Because we have a single event loop for multiple windows, every time I've mentioned "focused" above, I more precisely mean, "if at least one bevy window is focused".
- Due to a platform bug in winit (https://github.com/rust-windowing/winit/issues/1619), we can't simply use `Window::request_redraw()`. As a workaround, this PR will temporarily set the window mode to `Poll` when a redraw is requested. This is then reset to the user's `WinitConfig` setting on the next frame.
This adds a new WinitConfig resource that can be used to configure the behavior of winit.
When `return_from_run` is set to `true`, `App::run()` will return on `target_os` configurations that
support it.
Closesbevyengine/bevy#167.
