fix rtt copy/move

src/canvas_layer.h

@@ -10,9 +10,19 @@ struct LayerFrame
     std::array<bool, 6> m_dirty_face = SIXPLETTE(false);
     int m_duration = 1;
     int w = 0, h = 0;
-    LayerFrame() = default;
+
+    //// default
+    //LayerFrame() = default;
+    //// copy
+    //LayerFrame(const LayerFrame&) = delete;
+    //LayerFrame& operator=(const LayerFrame&) = delete;
+    //// move
+    //LayerFrame(LayerFrame&& other);
+    //LayerFrame& operator=(LayerFrame&&);
+
     bool create(int width, int height, int duration = 1);
     bool resize(int width, int height);
+    void clear(const glm::vec4& c);
 };
 
 class Layer