metal: clear damage before adding full damage

src/backends/metal/video.rs

@@ -3332,6 +3332,7 @@ impl RenderBuffer {
     pub fn damage_full(&self) {
         let dmabuf = self.dev_bo.dmabuf();
         let rect = Rect::new_sized_unchecked(0, 0, dmabuf.width, dmabuf.height);
+        self.damage_queue.clear_all();
         self.damage_queue.damage(&[rect]);
     }
 }

src/rect/region.rs

@@ -327,6 +327,13 @@ impl DamageQueue {
         data.clear();
     }
 
+    pub fn clear_all(&self) {
+        let datas = unsafe { self.datas.get().deref_mut() };
+        for data in datas {
+            data.clear();
+        }
+    }
+
     pub fn get(&self) -> Region {
         let data = unsafe { &self.datas.get().deref()[self.this] };
         Region::from_rects2(data)