remove context from ui (again) and create weird trait for it

src/testing/input.rs

@@ -9,7 +9,7 @@ pub struct Input {
 }
 
 impl Input {
-    pub fn event(&mut self, event: &WindowEvent) {
+    pub fn event(&mut self, event: &WindowEvent) -> bool {
         match event {
             WindowEvent::CursorMoved { position, .. } => {
                 self.cursor.pos = Vec2::new(position.x as f32, position.y as f32);
@@ -28,8 +28,9 @@ impl Input {
             WindowEvent::CursorLeft { .. } => {
                 self.cursor.exists = false;
             }
-            _ => (),
+            _ => return false,
         }
+        true
     }
 
     pub fn end_frame(&mut self) {