Add example for customized window decorations

Signed-off-by: Yureka <yuka@yuka.dev>

examples/customized-window-decorations.rs

@@ -0,0 +1,79 @@
+use cosmic::iced::{Color, Rectangle, Size};
+use cosmic::widget;
+use cosmic::widget::canvas;
+use cosmic_comp::hooks::{Decorations, Hooks};
+use cosmic_comp::shell::element::stack::{
+    DefaultDecorations as DefaultStackDecorations, TAB_HEIGHT,
+};
+use cosmic_comp::shell::element::window::{
+    DefaultDecorations as DefaultWindowDecorations, SSD_HEIGHT,
+};
+use std::sync::Arc;
+
+/// The struct implementing Decorations hook
+#[derive(Debug)]
+struct AddIndicator<Lower> {
+    lower: Lower,
+    height: i32,
+}
+
+/// An iced program drawing a circle, which we'll add to the window decorations
+struct Circle {
+    radius: f32,
+    color: Color,
+}
+
+impl<Message, Theme, Renderer: cosmic::iced_renderer::geometry::Renderer>
+    canvas::Program<Message, Theme, Renderer> for Circle
+{
+    type State = ();
+
+    fn draw(
+        &self,
+        _state: &(),
+        renderer: &Renderer,
+        _theme: &Theme,
+        bounds: Rectangle,
+        _cursor: cosmic::iced::mouse::Cursor,
+    ) -> Vec<Renderer::Geometry> {
+        let bounds = bounds.size();
+        let min = bounds.height.min(bounds.width);
+        let mut frame = canvas::Frame::new(renderer, Size::new(min, min));
+        let circle = canvas::Path::circle(frame.center(), self.radius);
+        frame.fill(&circle, self.color);
+        vec![frame.into_geometry()]
+    }
+}
+
+impl<Internal, Message: std::clone::Clone + 'static, Lower: Decorations<Internal, Message>>
+    Decorations<Internal, Message> for AddIndicator<Lower>
+{
+    fn view(&self, window: &Internal) -> cosmic::Element<'_, Message> {
+        let orig = self.lower.view(window);
+        widget::row()
+            .push(
+                widget::column()
+                    .push(canvas(Circle {
+                        radius: (self.height as f32 / 2.) * 0.8,
+                        color: Color::new(1.0, 0.0, 0.0, 1.0),
+                    }))
+                    .width(self.height as f32),
+            )
+            .push(orig)
+            .into()
+    }
+}
+
+/// The customized cosmic-comp entrypoint
+fn main() -> Result<(), Box<dyn std::error::Error>> {
+    cosmic_comp::run(Hooks {
+        window_decorations: Some(Arc::new(AddIndicator {
+            height: SSD_HEIGHT,
+            lower: DefaultWindowDecorations,
+        })),
+        stack_decorations: Some(Arc::new(AddIndicator {
+            height: TAB_HEIGHT,
+            lower: DefaultStackDecorations,
+        })),
+    })
+}