add undo action for bucket fill

src/canvas.h

@@ -66,6 +66,16 @@ class Canvas
     };
 
 public:
+    struct FloodData
+    {
+        std::shared_ptr<Layer> layer;
+        std::unique_ptr<bool[]> mask[6];
+        std::unique_ptr<glm::u8vec4[]> rgb[6] = SIXPLETTE(0);
+        bool dirty[6] = SIXPLETTE(false);
+        glm::vec4 bb[6];
+        void apply();
+    };
+
     Plane m_plane;
     Plane m_plane_brush;
     DynamicShape m_brush_shape;
@@ -166,7 +176,7 @@ public:
     void layer_add(std::string name, std::shared_ptr<Layer> layer = nullptr, int index = 0);
     void layer_order(int idx, int pos);
     void layer_merge(int source_idx, int dest_idx);
-    void flood_fill(int layer, int plane, std::vector<glm::ivec2> pos, std::map<int, std::unique_ptr<bool[]>>& plane_mask,
+    void flood_fill(int layer, int plane, std::vector<glm::ivec2> pos, FloodData& plane_data,
         float threshold, glm::vec4 dest_color, std::unique_ptr<glm::vec4>& source_color);
     void stroke_start(glm::vec3 point, float pressure);
     void stroke_update(glm::vec3 point, float pressure);