bevy/examples/ui/relative_cursor_position.rs
Carter Anderson dcc03724a5 Base Sets (#7466)
# Objective

NOTE: This depends on #7267 and should not be merged until #7267 is merged. If you are reviewing this before that is merged, I highly recommend viewing the Base Sets commit instead of trying to find my changes amongst those from #7267.

"Default sets" as described by the [Stageless RFC](https://github.com/bevyengine/rfcs/pull/45) have some [unfortunate consequences](https://github.com/bevyengine/bevy/discussions/7365).

## Solution

This adds "base sets" as a variant of `SystemSet`:

A set is a "base set" if `SystemSet::is_base` returns `true`. Typically this will be opted-in to using the `SystemSet` derive:

```rust
#[derive(SystemSet, Clone, Hash, Debug, PartialEq, Eq)]
#[system_set(base)]
enum MyBaseSet {
  A,
  B,
}
``` 

**Base sets are exclusive**: a system can belong to at most one "base set". Adding a system to more than one will result in an error. When possible we fail immediately during system-config-time with a nice file + line number. For the more nested graph-ey cases, this will fail at the final schedule build. 

**Base sets cannot belong to other sets**: this is where the word "base" comes from

Systems and Sets can only be added to base sets using `in_base_set`. Calling `in_set` with a base set will fail. As will calling `in_base_set` with a normal set.

```rust
app.add_system(foo.in_base_set(MyBaseSet::A))
       // X must be a normal set ... base sets cannot be added to base sets
       .configure_set(X.in_base_set(MyBaseSet::A))
```

Base sets can still be configured like normal sets:

```rust
app.add_system(MyBaseSet::B.after(MyBaseSet::Ap))
``` 

The primary use case for base sets is enabling a "default base set":

```rust
schedule.set_default_base_set(CoreSet::Update)
  // this will belong to CoreSet::Update by default
  .add_system(foo)
  // this will override the default base set with PostUpdate
  .add_system(bar.in_base_set(CoreSet::PostUpdate))
```

This allows us to build apis that work by default in the standard Bevy style. This is a rough analog to the "default stage" model, but it use the new "stageless sets" model instead, with all of the ordering flexibility (including exclusive systems) that it provides.

---

## Changelog

- Added "base sets" and ported CoreSet to use them.

## Migration Guide

TODO
2023-02-06 03:10:08 +00:00

81 lines
2.8 KiB
Rust

//! Showcases the `RelativeCursorPosition` component, used to check the position of the cursor relative to a UI node.
use bevy::{prelude::*, ui::RelativeCursorPosition, winit::WinitSettings};
fn main() {
App::new()
.add_plugins(DefaultPlugins)
// Only run the app when there is user input. This will significantly reduce CPU/GPU use.
.insert_resource(WinitSettings::desktop_app())
.add_startup_system(setup)
.add_system(relative_cursor_position_system)
.run();
}
fn setup(mut commands: Commands, asset_server: Res<AssetServer>) {
commands.spawn(Camera2dBundle::default());
commands
.spawn(NodeBundle {
style: Style {
size: Size::new(Val::Percent(100.0), Val::Percent(100.0)),
align_items: AlignItems::Center,
justify_content: JustifyContent::Center,
flex_direction: FlexDirection::Column,
..default()
},
..default()
})
.with_children(|parent| {
parent
.spawn(NodeBundle {
style: Style {
size: Size::new(Val::Px(250.0), Val::Px(250.0)),
margin: UiRect::new(Val::Px(0.), Val::Px(0.), Val::Px(0.), Val::Px(15.)),
..default()
},
background_color: Color::rgb(235., 35., 12.).into(),
..default()
})
.insert(RelativeCursorPosition::default());
parent.spawn(TextBundle {
text: Text::from_section(
"(0.0, 0.0)",
TextStyle {
font: asset_server.load("fonts/FiraSans-Bold.ttf"),
font_size: 40.0,
color: Color::rgb(0.9, 0.9, 0.9),
},
),
..default()
});
});
}
/// This systems polls the relative cursor position and displays its value in a text component.
fn relative_cursor_position_system(
relative_cursor_position_query: Query<&RelativeCursorPosition>,
mut output_query: Query<&mut Text>,
) {
let relative_cursor_position = relative_cursor_position_query.single();
let mut output = output_query.single_mut();
output.sections[0].value =
if let Some(relative_cursor_position) = relative_cursor_position.normalized {
format!(
"({:.1}, {:.1})",
relative_cursor_position.x, relative_cursor_position.y
)
} else {
"unknown".to_string()
};
output.sections[0].style.color = if relative_cursor_position.mouse_over() {
Color::rgb(0.1, 0.9, 0.1)
} else {
Color::rgb(0.9, 0.1, 0.1)
};
}