implement simple stroke undo based on actions history

engine/canvas.h

@@ -4,6 +4,7 @@
 #include "shader.h"
 #include "shape.h"
 #include "brush.h"
+#include "action.h"
 
 NS_START
 
@@ -15,14 +16,14 @@ class Canvas
 public:
     bool m_erase = false;
     glm::mat4 m_mvp;
+    glm::vec4 m_box;
     int m_width;
     int m_height;
     bool m_use_instanced = false;
     int m_current_layer_idx = 0;
-    Stroke* m_current_stroke = nullptr;
+    std::unique_ptr<Stroke> m_current_stroke;
     bool m_show_tmp = false;
     std::vector<Layer> m_layers;
-    std::vector<Stroke> m_strokes;
     std::vector<int> m_order;
     RTT m_tmp;
     Texture2D m_tex;
@@ -42,4 +43,28 @@ public:
     void clear(const glm::vec4& color = { 1, 1, 1, 1 });
 };
 
+
+class ActionStroke : public Action
+{
+public:
+    std::unique_ptr<Stroke> m_stroke;
+    std::unique_ptr<uint8_t[]> m_image;
+    glm::ivec4 m_box;
+    int m_layer_idx;
+    Canvas* m_canvas;
+    virtual void run() override
+    {
+        
+    }
+    virtual void undo() override
+    {
+        m_canvas->m_layers[m_stroke->m_layer].m_rtt.bindTexture();
+
+        glm::vec2 box_sz = m_box.zw() - m_box.xy();
+        glTexSubImage2D(GL_TEXTURE_2D, 0, m_box.x, m_box.y, box_sz.x, box_sz.y, GL_RGBA, GL_UNSIGNED_BYTE, m_image.get());
+
+        m_canvas->m_layers[m_stroke->m_layer].m_rtt.unbindTexture();
+    }
+};
+
 NS_END