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/// Example: Group opacity effect
///
/// Demonstrates using the effect system to apply group opacity to a parent shape
/// and all its children, so they composite as a single translucent layer rather
/// than individually blending with the background.
///
/// The scene has:
/// - A background shape (full opacity, not part of any effect group)
/// - A "group" parent shape with 50% opacity effect
/// - Two overlapping child shapes clipped to the parent
/// - A second group with 80% opacity
/// - Its own child shape
use futures::executor::block_on;
use grafo::Shape;
use grafo::{Color, ShapeDrawCommandOptions, Stroke};
use std::sync::Arc;
use winit::application::ApplicationHandler;
use winit::event::WindowEvent;
use winit::event_loop::{ActiveEventLoop, EventLoop};
use winit::window::{Window, WindowId};
const OPACITY_EFFECT: u64 = 1;
#[derive(Default)]
struct App<'a> {
window: Option<Arc<Window>>,
renderer: Option<grafo::Renderer<'a>>,
effect_loaded: bool,
}
impl<'a> ApplicationHandler for App<'a> {
fn resumed(&mut self, event_loop: &ActiveEventLoop) {
let window = Arc::new(
event_loop
.create_window(
Window::default_attributes().with_title("Grafo – Group Opacity Effect"),
)
.unwrap(),
);
let window_size = window.inner_size();
let scale_factor = window.scale_factor();
let physical_size = (window_size.width, window_size.height);
let mut renderer = block_on(grafo::Renderer::new(
window.clone(),
physical_size,
scale_factor,
true,
false,
1,
));
// Load the opacity effect shader once
let opacity_wgsl = r#"
struct Params {
opacity: f32,
}
@group(1) @binding(0) var<uniform> params: Params;
@fragment
fn effect_main(@location(0) uv: vec2<f32>) -> @location(0) vec4<f32> {
let color = textureSample(t_input, s_input, uv);
return color * params.opacity;
}
"#;
renderer
.load_effect(OPACITY_EFFECT, &[opacity_wgsl])
.expect("Failed to compile opacity effect");
self.effect_loaded = true;
self.window = Some(window);
self.renderer = Some(renderer);
}
fn window_event(
&mut self,
event_loop: &ActiveEventLoop,
window_id: WindowId,
event: WindowEvent,
) {
let Some(window) = &self.window else { return };
let Some(renderer) = &mut self.renderer else {
return;
};
if window_id != window.id() {
return;
}
match event {
WindowEvent::CloseRequested => event_loop.exit(),
WindowEvent::Resized(physical_size) => {
let new_size = (physical_size.width, physical_size.height);
renderer.resize(new_size);
window.request_redraw();
}
WindowEvent::RedrawRequested => {
// ── Background (no effect) ───────────────────────────────
let bg = Shape::rect(
[(50.0, 50.0), (750.0, 550.0)],
Stroke::new(2.0, Color::BLACK),
);
let _bg_id = renderer
.add_shape(
bg,
None,
None,
ShapeDrawCommandOptions::new().color(Color::rgb(200, 200, 220)),
)
.unwrap();
// ── Group 1: 50% opacity ─────────────────────────────────
let group1_bg = Shape::rect(
[(100.0, 100.0), (400.0, 350.0)],
Stroke::new(0.0, Color::TRANSPARENT),
);
let group1 = renderer
.add_shape(
group1_bg,
None,
None,
ShapeDrawCommandOptions::new().color(Color::rgb(255, 100, 100)),
)
.unwrap();
// Child 1: overlapping blue rectangle
let child1 = Shape::rect(
[(120.0, 120.0), (300.0, 250.0)],
Stroke::new(2.0, Color::BLACK),
);
renderer
.add_shape(
child1,
Some(group1),
None,
ShapeDrawCommandOptions::new().color(Color::rgb(50, 100, 255)),
)
.unwrap();
// Child 2: overlapping green rectangle
let child2 = Shape::rect(
[(200.0, 180.0), (380.0, 320.0)],
Stroke::new(2.0, Color::BLACK),
);
renderer
.add_shape(
child2,
Some(group1),
None,
ShapeDrawCommandOptions::new().color(Color::rgb(50, 200, 50)),
)
.unwrap();
// Attach 50% opacity to group1
let opacity: f32 = 0.5;
renderer
.set_group_effect(group1, OPACITY_EFFECT, bytemuck::bytes_of(&opacity))
.expect("Failed to set effect");
// ── Group 2: 80% opacity ─────────────────────────────────
let group2_bg = Shape::rect(
[(350.0, 100.0), (700.0, 350.0)],
Stroke::new(0.0, Color::TRANSPARENT),
);
let group2 = renderer
.add_shape(
group2_bg,
None,
None,
ShapeDrawCommandOptions::new().color(Color::rgb(255, 200, 50)),
)
.unwrap();
let child3 = Shape::rect(
[(370.0, 130.0), (680.0, 320.0)],
Stroke::new(2.0, Color::BLACK),
);
renderer
.add_shape(
child3,
Some(group2),
None,
ShapeDrawCommandOptions::new().color(Color::rgb(128, 0, 200)),
)
.unwrap();
let opacity2: f32 = 0.8;
renderer
.set_group_effect(group2, OPACITY_EFFECT, bytemuck::bytes_of(&opacity2))
.expect("Failed to set effect");
// ── Render ───────────────────────────────────────────────
match renderer.render() {
Ok(_) => {
renderer.clear_draw_queue();
}
Err(wgpu::SurfaceError::Lost) => renderer.resize(renderer.size()),
Err(wgpu::SurfaceError::OutOfMemory) => event_loop.exit(),
Err(e) => eprintln!("{e:?}"),
}
}
_ => {}
}
}
}
pub fn main() {
env_logger::init();
let event_loop = EventLoop::new().expect("To create the event loop");
let mut app = App::default();
let _ = event_loop.run_app(&mut app);
}