drag canvas, render layers and tmp, add/select layer, opacity for layer, color bucket filler

engine/canvas.h

@@ -11,18 +11,18 @@ class Canvas
 {
     Plane m_plane;
     BrushMesh m_mesh;
-    int m_current_layer_idx = 0;
     bool m_dirty = false;
 public:
     int m_width;
     int m_height;
     bool m_use_instanced = false;
+    int m_current_layer_idx = 0;
     Stroke* m_current_stroke = nullptr;
     bool m_show_tmp = false;
     std::vector<Layer> m_layers;
     std::vector<Stroke> m_strokes;
     RTT m_tmp;
-    RTT m_fb;
+    //RTT m_fb;
     Texture2D m_tex;
     Texture2D m_tex2;
     Sampler m_sampler;
@@ -36,7 +36,7 @@ public:
     void stroke_draw();
     void stroke_end();
     void stroke_commit();
-    void clear();
+    void clear(const glm::vec4& color = { 0, 0, 0, 1 });
 };
 
 NS_END