fix: isolate close animation to departing window

compositor/src/state.rs

@@ -81,6 +81,31 @@ use crate::{
     window_rules::{WindowRule, resolve as resolve_window_rules},
 };
 
+const CLOSE_ANIMATION_DURATION: Duration = Duration::from_millis(140);
+
+#[derive(Clone, Copy, Debug, Default)]
+struct ClosingAnimation {
+    progress: f64,
+    close_sent: bool,
+}
+
+impl ClosingAnimation {
+    fn advance(&mut self, delta: Duration) -> bool {
+        if self.close_sent {
+            return false;
+        }
+
+        self.progress =
+            (self.progress + delta.as_secs_f64() / CLOSE_ANIMATION_DURATION.as_secs_f64()).min(1.0);
+        if self.progress < 1.0 {
+            return false;
+        }
+
+        self.close_sent = true;
+        true
+    }
+}
+
 pub struct Ferese {
     pub start_time: Instant,
     pub socket_name: OsString,
@@ -96,6 +121,7 @@ pub struct Ferese {
     pub(crate) window_borders: HashMap<WindowId, crate::winit::WindowBorderBuffers>,
     pub(crate) window_shadows: HashMap<WindowId, crate::winit::WindowShadowBuffers>,
     pub(crate) rounded_clip_programs: HashMap<ErasedContextId, crate::winit::RoundedClipPrograms>,
+    closing_windows: HashMap<WindowId, ClosingAnimation>,
     viewport_animations: HashMap<WorkspaceId, AnimatedValue>,
     scrolling_world_x: HashMap<WindowId, (WorkspaceId, AnimatedValue)>,
     pub focused_window: Option<WindowId>,
@@ -401,6 +427,7 @@ impl Ferese {
             window_borders: HashMap::new(),
             window_shadows: HashMap::new(),
             rounded_clip_programs: HashMap::new(),
+            closing_windows: HashMap::new(),
             viewport_animations: HashMap::new(),
             scrolling_world_x: HashMap::new(),
             focused_window: None,
@@ -787,6 +814,7 @@ impl Ferese {
         self.window_geometry.remove(&id);
         self.window_borders.remove(&id);
         self.window_shadows.remove(&id);
+        self.closing_windows.remove(&id);
         self.window_rules_applied.remove(&id);
         self.scrolling_world_x.remove(&id);
         if let Err(error) = self.workspaces.remove_window(id) {
@@ -1045,6 +1073,18 @@ impl Ferese {
             .collect::<Vec<_>>();
         let mut active_animation = false;
 
+        let mut ready_to_close = Vec::new();
+        for (id, animation) in &mut self.closing_windows {
+            if animation.advance(delta) {
+                ready_to_close.push(*id);
+            } else if !animation.close_sent {
+                active_animation = true;
+            }
+        }
+        for id in ready_to_close {
+            self.send_window_close(id);
+        }
+
         for (workspace, viewport) in &mut self.viewport_animations {
             if !visible_workspaces.contains(workspace) {
                 continue;
@@ -1352,15 +1392,33 @@ impl Ferese {
         self.relayout();
     }
 
-    pub fn close_focused_window(&self) {
+    pub fn close_focused_window(&mut self) {
         let Some(focused) = self.focused_window else {
             return;
         };
-        let Some(toplevel) = self
-            .window_ids
-            .iter()
-            .find_map(|(window, id)| (*id == focused).then(|| window.toplevel()).flatten())
-        else {
+
+        if !self.animations_enabled {
+            self.send_window_close(focused);
+            return;
+        }
+
+        self.closing_windows.entry(focused).or_default();
+        crate::backends::direct::render_all(self);
+    }
+
+    pub(crate) fn closing_visual(&self, id: WindowId) -> (f64, f32) {
+        let Some(animation) = self.closing_windows.get(&id) else {
+            return (1.0, 1.0);
+        };
+        let eased = smoothstep(animation.progress);
+
+        (1.0 - eased * 0.02, (1.0 - eased) as f32)
+    }
+
+    fn send_window_close(&self, id: WindowId) {
+        let Some(toplevel) = self.window_ids.iter().find_map(|(window, window_id)| {
+            (*window_id == id).then(|| window.toplevel()).flatten()
+        }) else {
             return;
         };
 
@@ -1591,6 +1649,12 @@ fn centered_floating_rect(bounds: Rect) -> Rect {
     )
 }
 
+fn smoothstep(progress: f64) -> f64 {
+    let progress = progress.clamp(0.0, 1.0);
+
+    progress * progress * (3.0 - 2.0 * progress)
+}
+
 fn centered_transient_rect(parent: Rect) -> Rect {
     let width = (parent.width * 0.75).clamp(1.0, 640.0);
     let height = (parent.height * 0.75).clamp(1.0, 480.0);
@@ -1633,4 +1697,22 @@ mod tests {
 
         assert_eq!(transient, Rect::new(280.0, 210.0, 640.0, 480.0));
     }
+
+    #[test]
+    fn close_easing_is_bounded_and_symmetric() {
+        assert_eq!(smoothstep(-1.0), 0.0);
+        assert_eq!(smoothstep(0.5), 0.5);
+        assert_eq!(smoothstep(2.0), 1.0);
+    }
+
+    #[test]
+    fn close_animation_delays_the_protocol_close_until_it_finishes() {
+        let mut animation = ClosingAnimation::default();
+
+        assert!(!animation.advance(Duration::from_millis(70)));
+        assert_eq!(animation.progress, 0.5);
+        assert!(animation.advance(Duration::from_millis(70)));
+        assert!(animation.close_sent);
+        assert!(!animation.advance(Duration::from_secs(1)));
+    }
 }

compositor/src/winit.rs

@@ -547,17 +547,19 @@ fn output_elements(
         .filter_map(|window| {
             let id = *state.window_ids.get(window)?;
             let visual = state.window_geometry.get(&id)?.visual.current;
+            let (close_scale, close_alpha) = state.closing_visual(id);
+            let visual = scaled_visual_rect(visual, close_scale);
             let fullscreen = state
                 .workspaces
                 .workspace_for_window(id)
                 .and_then(|workspace| state.workspaces.workspace(workspace))
                 .is_some_and(|workspace| workspace.fullscreen == Some(id));
 
-            Some((window.clone(), id, visual, fullscreen))
+            Some((window.clone(), id, visual, fullscreen, close_alpha))
         })
         .collect::<Vec<_>>();
 
-    for (window, id, visual, fullscreen) in windows {
+    for (window, id, visual, fullscreen, close_alpha) in windows {
         let constrain = Rectangle::<i32, Logical>::new(
             (
                 (visual.x - f64::from(output_geometry.loc.x)).round() as i32,
@@ -588,6 +590,7 @@ fn output_elements(
             } else {
                 state.theme_settings.border_color.0
             };
+            let border_color = color_with_alpha(border_color, close_alpha);
 
             if let Some(border) = window_border_element(
                 state,
@@ -612,7 +615,7 @@ fn output_elements(
                 window_radius,
                 shadow_offset_y,
                 shadow_blur,
-                shadow_opacity,
+                shadow_opacity * f64::from(close_alpha),
                 shadow_color,
                 output,
                 &programs,
@@ -623,6 +626,7 @@ fn output_elements(
                 constrain,
                 scale,
                 window_radius,
+                close_alpha,
                 output,
                 programs.texture.clone(),
             ));
@@ -886,6 +890,7 @@ fn rounded_window_elements(
     constrain: Rectangle<i32, Logical>,
     scale: f64,
     requested_radius: f64,
+    alpha: f32,
     output: &Output,
     program: GlesTexProgram,
 ) -> Vec<AnimatedWindowRenderElement> {
@@ -921,7 +926,7 @@ fn rounded_window_elements(
                 popup.wl_surface(),
                 location + offset,
                 scale,
-                1.0,
+                alpha,
                 RenderElementKind::Unspecified,
             )
             .into_iter()
@@ -937,7 +942,7 @@ fn rounded_window_elements(
             surface,
             location,
             scale,
-            1.0,
+            alpha,
             RenderElementKind::Unspecified,
         )
         .into_iter()
@@ -965,6 +970,24 @@ fn rounded_window_elements(
     .collect()
 }
 
+fn scaled_visual_rect(rect: ferese_layout::Rect, scale: f64) -> ferese_layout::Rect {
+    let scale = scale.clamp(0.0, 1.0);
+    let width = rect.width * scale;
+    let height = rect.height * scale;
+
+    ferese_layout::Rect::new(
+        rect.x + (rect.width - width) / 2.0,
+        rect.y + (rect.height - height) / 2.0,
+        width,
+        height,
+    )
+}
+
+fn color_with_alpha(mut color: [f32; 4], alpha: f32) -> [f32; 4] {
+    color[3] *= alpha;
+    color
+}
+
 fn framebuffer_clip_rect(
     geometry: Rectangle<i32, Physical>,
     output_size: smithay::utils::Size<i32, Physical>,
@@ -1148,7 +1171,10 @@ fn normalized_scale(scale: f64) -> f64 {
 mod tests {
     use smithay::utils::{Logical, Physical, Rectangle, Transform};
 
-    use super::{framebuffer_clip_rect, normalized_scale, shadow_bounds};
+    use super::{
+        color_with_alpha, framebuffer_clip_rect, normalized_scale, scaled_visual_rect,
+        shadow_bounds,
+    };
 
     #[test]
     fn accepts_positive_finite_scale() {
@@ -1199,4 +1225,23 @@ mod tests {
             Rectangle::new((80, 54).into(), (440, 340).into())
         );
     }
+
+    #[test]
+    fn close_transform_scales_about_the_window_center() {
+        let rect = ferese_layout::Rect::new(100.0, 50.0, 400.0, 300.0);
+
+        assert_eq!(
+            scaled_visual_rect(rect, 0.98),
+            ferese_layout::Rect::new(104.0, 53.0, 392.0, 294.0)
+        );
+        assert_eq!(scaled_visual_rect(rect, 1.0), rect);
+    }
+
+    #[test]
+    fn close_opacity_only_changes_the_alpha_channel() {
+        assert_eq!(
+            color_with_alpha([0.2, 0.4, 0.6, 0.8], 0.5),
+            [0.2, 0.4, 0.6, 0.4]
+        );
+    }
 }