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box-shadow clipping fix (#16790)

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# Objective

Instead of clipping the non-visable sections of box-shadows, the shadow
is scaled to fit into the remaining area after clipping because the
normalized coordinates that are meant to border the unclipped subsection
of the shadow are always set to `[Vec2::ZERO, Vec2::X, Vec2::ONE,
Vec2::Y]`,

## Solution

Calculate the coordinates for the corners of the visible area.

## Testing

Test app:

```rust
use bevy::color::palettes::css::RED;
use bevy::color::palettes::css::WHITE;
use bevy::prelude::*;

fn main() {
    App::new()
        .add_plugins(DefaultPlugins)
        .add_systems(Startup, setup)
        .run();
}

fn setup(mut commands: Commands) {
    commands.spawn(Camera2d);
    commands
        .spawn(Node {
            ..Default::default()
        })
        .with_children(|commands| {
            commands
                .spawn((
                    Node {
                        width: Val::Px(100.),
                        height: Val::Px(100.),
                        margin: UiRect {
                            left: Val::Px(100.),
                            top: Val::Px(300.),
                            ..Default::default()
                        },
                        overflow: Overflow::clip(),
                        ..Default::default()
                    },
                    BackgroundColor(WHITE.into()),
                ))
                .with_children(|commands| {
                    commands.spawn((
                        Node {
                            position_type: PositionType::Absolute,
                            left: Val::Px(50.),
                            top: Val::Px(50.),
                            width: Val::Px(100.),
                            height: Val::Px(100.),
                            ..Default::default()
                        },
                        BackgroundColor(RED.into()),
                        BoxShadow::from(ShadowStyle {
                            x_offset: Val::ZERO,
                            y_offset: Val::ZERO,
                            spread_radius: Val::Px(50.),
                            blur_radius: Val::Px(6.),
                            ..Default::default()
                        }),
                    ));
                });
        });
}
```

Main:
<img width="103" alt="bad_shadow"
src="https://github.com/user-attachments/assets/6f7ade0e-959f-4d18-92e8-903630eb8cd3"
/>

This PR:
<img width="98" alt="clipped_shadow"
src="https://github.com/user-attachments/assets/7f576c94-908c-4fe6-abaa-f18fefe05207"
/>
This commit is contained in:
ickshonpe 2024-12-13 21:35:39 +00:00 committed by GitHub
parent 4ba47ed8bf
commit 30bd641af4
No known key found for this signature in database
GPG Key ID: B5690EEEBB952194
1 changed files with 20 additions and 9 deletions
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29
crates/bevy_ui/src/render/box_shadow.rs
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@ -217,7 +217,7 @@ impl SpecializedRenderPipeline for BoxShadowPipeline {
pub struct ExtractedBoxShadow {
pub stack_index: u32,
pub transform: Mat4,
pub rect: Rect,
pub bounds: Vec2,
pub clip: Option<Rect>,
pub camera_entity: Entity,
pub color: LinearRgba,
@ -323,10 +323,7 @@ pub fn extract_shadows(
transform: transform.compute_matrix()
* Mat4::from_translation(offset.extend(0.)),
color: drop_shadow.color.into(),
rect: Rect {
min: Vec2::ZERO,
max: shadow_size + 6. * blur_radius,
},
bounds: shadow_size + 6. * blur_radius,
clip: clip.map(|clip| clip.clip),
camera_entity,
radius,
@ -415,9 +412,7 @@ pub fn prepare_shadows(
while item_index < ui_phase.items.len() {
let item = &mut ui_phase.items[item_index];
if let Some(box_shadow) = extracted_shadows.box_shadows.get(item.entity()) {
let uinode_rect = box_shadow.rect;
let rect_size = uinode_rect.size().extend(1.0);
let rect_size = box_shadow.bounds.extend(1.0);
// Specify the corners of the node
let positions = QUAD_VERTEX_POSITIONS
@ -479,7 +474,23 @@ pub fn prepare_shadows(
box_shadow.radius.bottom_left,
];
let uvs = [Vec2::ZERO, Vec2::X, Vec2::ONE, Vec2::Y];
let uvs = [
Vec2::new(positions_diff[0].x, positions_diff[0].y),
Vec2::new(
box_shadow.bounds.x + positions_diff[1].x,
positions_diff[1].y,
),
Vec2::new(
box_shadow.bounds.x + positions_diff[2].x,
box_shadow.bounds.y + positions_diff[2].y,
),
Vec2::new(
positions_diff[3].x,
box_shadow.bounds.y + positions_diff[3].y,
),
]
.map(|pos| pos / box_shadow.bounds);
for i in 0..4 {
ui_meta.vertices.push(BoxShadowVertex {
position: positions_clipped[i].into(),