metal: track per-framebuffer damage

src/rect.rs

@@ -164,6 +164,11 @@ impl Rect {
         self.raw.x1 == self.raw.x2 || self.raw.y1 == self.raw.y2
     }
 
+    #[expect(dead_code)]
+    pub fn is_not_empty(&self) -> bool {
+        !self.is_empty()
+    }
+
     #[expect(dead_code)]
     pub fn to_origin(&self) -> Self {
         Self {