feat: move tiled windows directionally

compositor/src/input.rs

@@ -34,11 +34,7 @@ impl Ferese {
                             return FilterResult::Intercept(());
                         }
 
-                        let direction = if modifiers.logo
-                            && !modifiers.ctrl
-                            && !modifiers.alt
-                            && !modifiers.shift
-                        {
+                        let direction = if modifiers.logo && !modifiers.ctrl && !modifiers.alt {
                             match keysym.modified_sym().raw() {
                                 keysyms::KEY_h | keysyms::KEY_H => Some(Direction::Left),
                                 keysyms::KEY_j | keysyms::KEY_J => Some(Direction::Down),
@@ -53,7 +49,11 @@ impl Ferese {
                         if let Some(direction) = direction {
                             if state == KeyState::Pressed {
                                 data.intercepted_keys.insert(keycode);
-                                data.focus_direction(direction);
+                                if modifiers.shift {
+                                    data.move_direction(direction);
+                                } else {
+                                    data.focus_direction(direction);
+                                }
                             }
 
                             FilterResult::Intercept(())

compositor/src/state.rs

@@ -278,6 +278,21 @@ impl Ferese {
         }
     }
 
+    pub fn move_direction(&mut self, direction: Direction) {
+        let Some(current) = self.focused_window else {
+            return;
+        };
+        let Some(bounds) = self.output_bounds() else {
+            return;
+        };
+
+        match self.layout.move_window(current, direction, bounds) {
+            Ok(true) => self.relayout(),
+            Ok(false) => {}
+            Err(error) => tracing::error!(%error, ?current, "failed to move tiled window"),
+        }
+    }
+
     fn output_bounds(&self) -> Option<Rect> {
         let output = self.space.outputs().next()?;
         let geometry = self.space.output_geometry(output)?;

crates/ferese-layout/src/lib.rs

@@ -342,6 +342,35 @@ impl LayoutTree {
             .map(|(candidate, _, _, _)| candidate))
     }
 
+    pub fn move_window(
+        &mut self,
+        window: WindowId,
+        direction: Direction,
+        bounds: Rect,
+    ) -> Result<bool, LayoutError> {
+        let Some(neighbor) = self.directional_neighbor(window, direction, bounds)? else {
+            return Ok(false);
+        };
+        let window_node = self
+            .windows
+            .get(&window)
+            .copied()
+            .ok_or(LayoutError::UnknownWindow(window))?;
+        let neighbor_node = self
+            .windows
+            .get(&neighbor)
+            .copied()
+            .ok_or(LayoutError::UnknownWindow(neighbor))?;
+
+        self.nodes.insert(window_node, Node::Window(neighbor));
+        self.nodes.insert(neighbor_node, Node::Window(window));
+        self.windows.insert(window, neighbor_node);
+        self.windows.insert(neighbor, window_node);
+
+        debug_assert!(self.validate().is_ok());
+        Ok(true)
+    }
+
     pub fn validate(&self) -> Result<(), LayoutError> {
         let Some(root) = self.root else {
             return if self.nodes.is_empty() && self.parents.is_empty() && self.windows.is_empty() {
@@ -711,4 +740,41 @@ mod tests {
             None
         );
     }
+
+    #[test]
+    fn directional_move_swaps_window_leaves() {
+        let mut tree = LayoutTree::default();
+        tree.insert(WindowId(1), None, Axis::Horizontal, 0.5)
+            .unwrap();
+        tree.insert(WindowId(2), Some(WindowId(1)), Axis::Horizontal, 0.5)
+            .unwrap();
+        let bounds = Rect::new(0.0, 0.0, 100.0, 80.0);
+
+        assert!(
+            tree.move_window(WindowId(1), Direction::Right, bounds)
+                .unwrap()
+        );
+
+        let geometry = tree.geometry(bounds).unwrap();
+        assert_eq!(geometry[&WindowId(2)].x, 0.0);
+        assert_eq!(geometry[&WindowId(1)].x, 50.0);
+        assert!(tree.validate().is_ok());
+    }
+
+    #[test]
+    fn directional_move_at_boundary_is_a_noop() {
+        let mut tree = LayoutTree::default();
+        tree.insert(WindowId(1), None, Axis::Horizontal, 0.5)
+            .unwrap();
+
+        assert!(
+            !tree
+                .move_window(
+                    WindowId(1),
+                    Direction::Left,
+                    Rect::new(0.0, 0.0, 100.0, 80.0),
+                )
+                .unwrap()
+        );
+    }
 }