Ignore clicks on uinodes outside of rounded corners

[ickshonpe]

Objective

Fixes #14941

Solution

1. Add a resolved_border_radius field to Node to hold the resolved border radius values.
2. Remove the border radius calculations from the UI's extraction functions.
3. Compute the border radius during UI relayouts in ui_layout_system and store them in Node.
4. New pick_rounded_rect function based on the border radius SDF from ui.wgsl.
5. Use pick_rounded_rect in focus and picking_backend to check if the pointer is hovering UI nodes with rounded corners.

---

Showcase

cargo run --example button

App.2024-08-28.15-28-19.mp4

Testing

Modified button example with buttons with different corner radius:

use bevy::{color::palettes::basic::*, prelude::*, 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_systems(Startup, setup)
        .add_systems(Update, button_system)
        .run();
}

const NORMAL_BUTTON: Color = Color::srgb(0.15, 0.15, 0.15);
const HOVERED_BUTTON: Color = Color::srgb(0.25, 0.25, 0.25);
const PRESSED_BUTTON: Color = Color::srgb(0.35, 0.75, 0.35);

fn button_system(
    mut interaction_query: Query<
        (
            &Interaction,
            &mut BackgroundColor,
            &mut BorderColor,
            &Children,
        ),
        (Changed<Interaction>, With<Button>),
    >,
    mut text_query: Query<&mut Text>,
) {
    for (interaction, mut color, mut border_color, children) in &mut interaction_query {
        let mut text = text_query.get_mut(children[0]).unwrap();
        match *interaction {
            Interaction::Pressed => {
                text.sections[0].value = "Press".to_string();
                *color = PRESSED_BUTTON.into();
                border_color.0 = RED.into();
            }
            Interaction::Hovered => {
                text.sections[0].value = "Hover".to_string();
                *color = HOVERED_BUTTON.into();
                border_color.0 = Color::WHITE;
            }
            Interaction::None => {
                text.sections[0].value = "Button".to_string();
                *color = NORMAL_BUTTON.into();
                border_color.0 = Color::BLACK;
            }
        }
    }
}

fn setup(mut commands: Commands, asset_server: Res<AssetServer>) {
    // ui camera
    commands.spawn(Camera2dBundle::default());
    commands
        .spawn(NodeBundle {
            style: Style {
                width: Val::Percent(100.0),
                height: Val::Percent(100.0),
                align_items: AlignItems::Center,
                justify_content: JustifyContent::Center,
                row_gap: Val::Px(10.),
                ..default()
            },
            ..default()
        })
        .with_children(|parent| {
            for border_radius in [
                BorderRadius {
                    top_left: Val::ZERO,
                    ..BorderRadius::MAX
                },
                BorderRadius {
                    top_right: Val::ZERO,
                    ..BorderRadius::MAX
                },
                BorderRadius {
                    bottom_right: Val::ZERO,
                    ..BorderRadius::MAX
                },
                BorderRadius {
                    bottom_left: Val::ZERO,
                    ..BorderRadius::MAX
                },
            ] {
                parent
                    .spawn(ButtonBundle {
                        style: Style {
                            width: Val::Px(150.0),
                            height: Val::Px(65.0),
                            border: UiRect::all(Val::Px(5.0)),
                            // horizontally center child text
                            justify_content: JustifyContent::Center,
                            // vertically center child text
                            align_items: AlignItems::Center,
                            ..default()
                        },
                        border_color: BorderColor(Color::BLACK),
                        border_radius,
                        background_color: NORMAL_BUTTON.into(),
                        ..default()
                    })
                    .with_child(TextBundle::from_section(
                        "Button",
                        TextStyle {
                            font: asset_server.load("fonts/FiraSans-Bold.ttf"),
                            font_size: 40.0,
                            color: Color::srgb(0.9, 0.9, 0.9),
                        },
                    ));
            }
        });
}

[NthTensor]

Looks generally correct to me. There might be a branchless way to do this, but it's probably not worth optimizing that for picking.

[alice-i-cecile]

@ickshonpe once merge conflicts are resolved I'd like to get this in ASAP :)

[ickshonpe]

@ickshonpe once merge conflicts are resolved I'd like to get this in ASAP :)

Should be ready now.

[CrazyboyQCD]

@ickshonpe
I think there is a more readable and efficient way to be branchless.
Godbolt link