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bevy/examples/window/window_drag_move.rs
Carter Anderson 015f2c69ca
Merge Style properties into Node. Use ComputedNode for computed properties. ()
# Objective

Continue improving the user experience of our UI Node API in the
direction specified by [Bevy's Next Generation Scene / UI
System](https://github.com/bevyengine/bevy/discussions/14437)

## Solution

As specified in the document above, merge `Style` fields into `Node`,
and move "computed Node fields" into `ComputedNode` (I chose this name
over something like `ComputedNodeLayout` because it currently contains
more than just layout info. If we want to break this up / rename these
concepts, lets do that in a separate PR). `Style` has been removed.

This accomplishes a number of goals:

## Ergonomics wins

Specifying both `Node` and `Style` is now no longer required for
non-default styles

Before:
```rust
commands.spawn((
    Node::default(),
    Style {
        width:  Val::Px(100.),
        ..default()
    },
));
```

After:

```rust
commands.spawn(Node {
    width:  Val::Px(100.),
    ..default()
});
```

## Conceptual clarity

`Style` was never a comprehensive "style sheet". It only defined "core"
style properties that all `Nodes` shared. Any "styled property" that
couldn't fit that mold had to be in a separate component. A "real" style
system would style properties _across_ components (`Node`, `Button`,
etc). We have plans to build a true style system (see the doc linked
above).

By moving the `Style` fields to `Node`, we fully embrace `Node` as the
driving concept and remove the "style system" confusion.

## Next Steps

* Consider identifying and splitting out "style properties that aren't
core to Node". This should not happen for Bevy 0.15.

---

## Migration Guide

Move any fields set on `Style` into `Node` and replace all `Style`
component usage with `Node`.

Before:
```rust
commands.spawn((
    Node::default(),
    Style {
        width:  Val::Px(100.),
        ..default()
    },
));
```

After:

```rust
commands.spawn(Node {
    width:  Val::Px(100.),
    ..default()
});
```

For any usage of the "computed node properties" that used to live on
`Node`, use `ComputedNode` instead:

Before:
```rust
fn system(nodes: Query<&Node>) {
    for node in &nodes {
        let computed_size = node.size();
    }
}
```

After:
```rust
fn system(computed_nodes: Query<&ComputedNode>) {
    for computed_node in &computed_nodes {
        let computed_size = computed_node.size();
    }
}
```
2024-10-18 22:25:33 +00:00

142 lines
4.5 KiB
Rust

//! This example illustrates drag move and drag resize without window
//! decorations.
//!
//! When window decorations are not present, the user cannot drag a window by
//! its titlebar to change its position. The `start_drag_move()` function
//! permits a users to drag a window by left clicking anywhere in the window;
//! left click must be pressed and other constraints can be imposed. For
//! instance an application could require a user to hold down alt and left click
//! to drag a window.
//!
//! The `start_drag_resize()` function behaves similarly but permits a window to
//! be resized.
use bevy::{math::CompassOctant, prelude::*};
/// Determine what do on left click.
#[derive(Resource, Debug)]
enum LeftClickAction {
/// Do nothing.
Nothing,
/// Move the window on left click.
Move,
/// Resize the window on left click.
Resize,
}
/// What direction index should the window resize toward.
#[derive(Resource)]
struct ResizeDir(usize);
/// Directions that the drag resizes the window toward.
const DIRECTIONS: [CompassOctant; 8] = [
CompassOctant::North,
CompassOctant::NorthEast,
CompassOctant::East,
CompassOctant::SouthEast,
CompassOctant::South,
CompassOctant::SouthWest,
CompassOctant::West,
CompassOctant::NorthWest,
];
fn main() {
App::new()
.add_plugins(DefaultPlugins.set(WindowPlugin {
primary_window: Some(Window {
decorations: false,
..default()
}),
..default()
}))
.insert_resource(ResizeDir(7))
.insert_resource(LeftClickAction::Move)
.add_systems(Startup, setup)
.add_systems(Update, (handle_input, move_or_resize_windows))
.run();
}
fn setup(mut commands: Commands) {
// Camera
commands.spawn(Camera3d::default());
// UI
commands
.spawn((
Node {
position_type: PositionType::Absolute,
padding: UiRect::all(Val::Px(5.0)),
..default()
},
BackgroundColor(Color::BLACK.with_alpha(0.75)),
GlobalZIndex(i32::MAX),
))
.with_children(|p| {
p.spawn(Text::default()).with_children(|p| {
p.spawn(TextSpan::new(
"Demonstrate drag move and drag resize without window decorations.\n\n",
));
p.spawn(TextSpan::new("Controls:\n"));
p.spawn(TextSpan::new("A - change left click action ["));
p.spawn(TextSpan::new("Move"));
p.spawn(TextSpan::new("]\n"));
p.spawn(TextSpan::new("S / D - change resize direction ["));
p.spawn(TextSpan::new("NorthWest"));
p.spawn(TextSpan::new("]\n"));
});
});
}
fn handle_input(
input: Res<ButtonInput<KeyCode>>,
mut action: ResMut<LeftClickAction>,
mut dir: ResMut<ResizeDir>,
example_text: Query<Entity, With<Text>>,
mut writer: TextUiWriter,
) {
use LeftClickAction::*;
if input.just_pressed(KeyCode::KeyA) {
*action = match *action {
Move => Resize,
Resize => Nothing,
Nothing => Move,
};
*writer.text(example_text.single(), 4) = format!("{:?}", *action);
}
if input.just_pressed(KeyCode::KeyS) {
dir.0 = dir
.0
.checked_sub(1)
.unwrap_or(DIRECTIONS.len().saturating_sub(1));
*writer.text(example_text.single(), 7) = format!("{:?}", DIRECTIONS[dir.0]);
}
if input.just_pressed(KeyCode::KeyD) {
dir.0 = (dir.0 + 1) % DIRECTIONS.len();
*writer.text(example_text.single(), 7) = format!("{:?}", DIRECTIONS[dir.0]);
}
}
fn move_or_resize_windows(
mut windows: Query<&mut Window>,
action: Res<LeftClickAction>,
input: Res<ButtonInput<MouseButton>>,
dir: Res<ResizeDir>,
) {
// Both `start_drag_move()` and `start_drag_resize()` must be called after a
// left mouse button press as done here.
//
// winit 0.30.5 may panic when initiated without a left mouse button press.
if input.just_pressed(MouseButton::Left) {
for mut window in windows.iter_mut() {
match *action {
LeftClickAction::Nothing => (),
LeftClickAction::Move => window.start_drag_move(),
LeftClickAction::Resize => {
let d = DIRECTIONS[dir.0];
window.start_drag_resize(d);
}
}
}
}
}