add focus event

native/src/window/event.rs

@@ -29,4 +29,7 @@ pub enum Event {
     /// There will be a single `FilesHoveredLeft` event triggered even if
     /// multiple files were hovered.
     FilesHoveredLeft,
+
+    /// A window was focused or not
+    Focused(bool),
 }

winit/src/conversion.rs

@@ -121,6 +121,9 @@ pub fn window_event(
         WindowEvent::Touch(touch) => {
             Some(Event::Touch(touch_event(*touch, scale_factor)))
         }
+        WindowEvent::Focused(focused) => {
+            Some(Event::Window(window::Event::Focused(*focused)))
+        }
         _ => None,
     }
 }