feat(cli): add focus-stack-window cmd

This commit adds a new command, focus-stack-window, which allows users
to focus windows in the focused container stack by their index
(zero-indexed) within the stack.

If the user tries to focus an index which does not correspond to a
window within the container stack, an error will be logged.

komorebi/src/core/mod.rs

@@ -45,12 +45,13 @@ pub enum SocketMessage {
     CycleFocusWindow(CycleDirection),
     CycleMoveWindow(CycleDirection),
     StackWindow(OperationDirection),
+    UnstackWindow,
+    CycleStack(CycleDirection),
+    FocusStackWindow(usize),
     StackAll,
     UnstackAll,
     ResizeWindowEdge(OperationDirection, Sizing),
     ResizeWindowAxis(Axis, Sizing),
-    UnstackWindow,
-    CycleStack(CycleDirection),
     MoveContainerToMonitorNumber(usize),
     CycleMoveContainerToMonitor(CycleDirection),
     MoveContainerToWorkspaceNumber(usize),

komorebi/src/process_command.rs

@@ -228,6 +228,10 @@ impl WindowManager {
                 self.cycle_container_window_in_direction(direction)?;
                 self.focused_window()?.focus(self.mouse_follows_focus)?;
             }
+            SocketMessage::FocusStackWindow(idx) => {
+                self.focus_container_window(idx)?;
+                self.focused_window()?.focus(self.mouse_follows_focus)?;
+            }
             SocketMessage::ForceFocus => {
                 let focused_window = self.focused_window()?;
                 let focused_window_rect = WindowsApi::window_rect(focused_window.hwnd())?;

komorebi/src/window_manager.rs

@@ -1534,6 +1534,31 @@ impl WindowManager {
         self.update_focused_workspace(self.mouse_follows_focus, true)
     }
 
+    #[tracing::instrument(skip(self))]
+    pub fn focus_container_window(&mut self, idx: usize) -> Result<()> {
+        self.handle_unmanaged_window_behaviour()?;
+
+        tracing::info!("focusing container window at index {idx}");
+
+        let container = self.focused_container_mut()?;
+
+        let len = NonZeroUsize::new(container.windows().len())
+            .ok_or_else(|| anyhow!("there must be at least one window in a container"))?;
+
+        if len.get() == 1 {
+            bail!("there is only one window in this container");
+        }
+
+        if container.windows().get(idx).is_none() {
+            bail!("there is no window in this container at index {idx}");
+        }
+
+        container.focus_window(idx);
+        container.load_focused_window();
+
+        self.update_focused_workspace(self.mouse_follows_focus, true)
+    }
+
     #[tracing::instrument(skip(self))]
     pub fn stack_all(&mut self) -> Result<()> {
         self.handle_unmanaged_window_behaviour()?;