Add focus change animations

5 files changed, 116 insertions, 11 deletions

diff --git a/Cargo.toml b/Cargo.toml
index 6720107a..8febe268 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -10,6 +10,7 @@ edition = "2021"
 anyhow = { version = "1.0.72", features = ["backtrace"] }
 bitflags = "2.3.3"
 clap = { version = "4.3.21", features = ["derive"] }
+keyframe = { version = "1.1.1", default-features = false }
 profiling = "1.0.9"
 smithay-drm-extras = { version = "0.1.0", path = "../smithay/smithay-drm-extras" }
 tracing = "0.1.37"
diff --git a/src/animation.rs b/src/animation.rs
new file mode 100644
index 00000000..27449243
--- /dev/null
+++ b/src/animation.rs
@@ -0,0 +1,46 @@
+use std::time::Duration;
+
+use keyframe::functions::EaseOutCubic;
+use keyframe::EasingFunction;
+
+use crate::utils::get_monotonic_time;
+
+#[derive(Debug)]
+pub struct Animation {
+    from: f64,
+    to: f64,
+    duration: Duration,
+    start_time: Duration,
+    current_time: Duration,
+}
+
+impl Animation {
+    pub fn new(from: f64, to: f64, over: Duration) -> Self {
+        // FIXME: ideally we shouldn't use current time here because animations started within the
+        // same frame cycle should have the same start time to be synchronized.
+        let now = get_monotonic_time();
+
+        Self {
+            from,
+            to,
+            duration: over,
+            start_time: now,
+            current_time: now,
+        }
+    }
+
+    pub fn set_current_time(&mut self, time: Duration) {
+        self.current_time = time;
+    }
+
+    pub fn is_done(&self) -> bool {
+        self.current_time >= self.start_time + self.duration
+    }
+
+    pub fn value(&self) -> f64 {
+        let passed = (self.current_time - self.start_time).as_secs_f64();
+        let total = self.duration.as_secs_f64();
+        let x = (passed / total).clamp(0., 1.);
+        EaseOutCubic.y(x) * (self.to - self.from) + self.from
+    }
+}
diff --git a/src/layout.rs b/src/layout.rs
index 2bda5cc8..bc2d5e54 100644
--- a/src/layout.rs
+++ b/src/layout.rs
@@ -44,6 +44,8 @@ use smithay::utils::{Logical, Point, Rectangle, Scale, Size};
 use smithay::wayland::compositor::{with_states, SurfaceData};
 use smithay::wayland::shell::xdg::XdgToplevelSurfaceData;
 
+use crate::animation::Animation;
+
 const PADDING: i32 = 16;
 
 #[derive(Debug, Clone, PartialEq, Eq)]
@@ -114,6 +116,9 @@ pub struct Workspace<W: LayoutElement> {
 
     /// Offset of the view computed from the active column.
     view_offset: i32,
+
+    /// Animation of the view offset, if one is currently ongoing.
+    view_offset_anim: Option<Animation>,
 }
 
 /// Width of a column.
@@ -770,6 +775,20 @@ impl<W: LayoutElement> MonitorSet<W> {
         })
     }
 
+    pub fn workspace_for_output_mut(&mut self, output: &Output) -> Option<&mut Workspace<W>> {
+        let MonitorSet::Normal { monitors, .. } = self else {
+            return None;
+        };
+
+        monitors.iter_mut().find_map(|monitor| {
+            if &monitor.output == output {
+                Some(&mut monitor.workspaces[monitor.active_workspace_idx])
+            } else {
+                None
+            }
+        })
+    }
+
     pub fn window_under(
         &self,
         output: &Output,
@@ -868,6 +887,20 @@ impl<W: LayoutElement> Workspace<W> {
             columns: vec![],
             active_column_idx: 0,
             view_offset: 0,
+            view_offset_anim: None,
+        }
+    }
+
+    pub fn advance_animations(&mut self, current_time: Duration) {
+        match &mut self.view_offset_anim {
+            Some(anim) => {
+                anim.set_current_time(current_time);
+                self.view_offset = anim.value().round() as i32;
+                if anim.is_done() {
+                    self.view_offset_anim = None;
+                }
+            }
+            None => (),
         }
     }
 
@@ -918,6 +951,25 @@ impl<W: LayoutElement> Workspace<W> {
         }
     }
 
+    fn activate_column(&mut self, idx: usize) {
+        if self.active_column_idx == idx {
+            return;
+        }
+
+        let current_x = self.view_pos();
+
+        self.active_column_idx = idx;
+
+        self.view_offset = 0;
+        let new_x = self.view_pos();
+
+        self.view_offset_anim = Some(Animation::new(
+            (current_x - new_x) as f64,
+            0.,
+            Duration::from_millis(250),
+        ));
+    }
+
     fn has_windows(&self) -> bool {
         self.windows().next().is_some()
     }
@@ -954,7 +1006,7 @@ impl<W: LayoutElement> Workspace<W> {
         self.columns.insert(idx, column);
 
         if activate {
-            self.active_column_idx = idx;
+            self.activate_column(idx);
         }
     }
 
@@ -978,7 +1030,7 @@ impl<W: LayoutElement> Workspace<W> {
                 return;
             }
 
-            self.active_column_idx = min(self.active_column_idx, self.columns.len() - 1);
+            self.activate_column(min(self.active_column_idx, self.columns.len() - 1));
             return;
         }
 
@@ -1004,22 +1056,24 @@ impl<W: LayoutElement> Workspace<W> {
         let column = &mut self.columns[column_idx];
 
         column.activate_window(window);
-        self.active_column_idx = column_idx;
+        self.activate_column(column_idx);
     }
 
     fn verify_invariants(&self) {
         assert!(self.view_size.w > 0);
         assert!(self.view_size.h > 0);
 
-        assert!(self.columns.is_empty() || self.active_column_idx < self.columns.len());
+        if !self.columns.is_empty() {
+            assert!(self.active_column_idx < self.columns.len());
 
-        for column in &self.columns {
-            column.verify_invariants();
+            for column in &self.columns {
+                column.verify_invariants();
+            }
         }
     }
 
     fn focus_left(&mut self) {
-        self.active_column_idx = self.active_column_idx.saturating_sub(1);
+        self.activate_column(self.active_column_idx.saturating_sub(1));
     }
 
     fn focus_right(&mut self) {
@@ -1027,7 +1081,7 @@ impl<W: LayoutElement> Workspace<W> {
             return;
         }
 
-        self.active_column_idx = min(self.active_column_idx + 1, self.columns.len() - 1);
+        self.activate_column(min(self.active_column_idx + 1, self.columns.len() - 1));
     }
 
     fn focus_down(&mut self) {
@@ -1053,7 +1107,7 @@ impl<W: LayoutElement> Workspace<W> {
         }
 
         self.columns.swap(self.active_column_idx, new_idx);
-        self.active_column_idx = new_idx;
+        self.activate_column(new_idx);
     }
 
     fn move_right(&mut self) {
@@ -1067,7 +1121,7 @@ impl<W: LayoutElement> Workspace<W> {
         }
 
         self.columns.swap(self.active_column_idx, new_idx);
-        self.active_column_idx = new_idx;
+        self.activate_column(new_idx);
     }
 
     fn move_down(&mut self) {
diff --git a/src/main.rs b/src/main.rs
index 49a8598d..d87a3a27 100644
--- a/src/main.rs
+++ b/src/main.rs
@@ -3,6 +3,7 @@ extern crate tracing;
 
 mod handlers;
 
+mod animation;
 mod backend;
 mod frame_clock;
 mod grabs;
diff --git a/src/niri.rs b/src/niri.rs
index 905f0738..714f8495 100644
--- a/src/niri.rs
+++ b/src/niri.rs
@@ -302,11 +302,14 @@ impl Niri {
     fn redraw(&mut self, backend: &mut dyn Backend, output: &Output) {
         let _span = tracy_client::span!("redraw");
         let state = self.output_state.get_mut(output).unwrap();
+        let presentation_time = state.frame_clock.next_presentation_time();
 
         assert!(state.queued_redraw.take().is_some());
         assert!(!state.waiting_for_vblank);
 
-        let elements = self.monitor_set.render_elements(backend.renderer(), output);
+        let ws = self.monitor_set.workspace_for_output_mut(output).unwrap();
+        ws.advance_animations(presentation_time);
+        let elements = ws.render_elements(backend.renderer());
 
         let output_pos = self.global_space.output_geometry(output).unwrap().loc;
         let pointer_pos = self.seat.get_pointer().unwrap().current_location() - output_pos.to_f64();