fix undo and redo

src/node_canvas.cpp

@@ -296,8 +296,25 @@ void NodeCanvas::draw()
                 m_blender_rtt.unbindTexture();
                 glActiveTexture(GL_TEXTURE0);
                 m_blender_rtt.unbindTexture();
-
             }
+
+#ifdef _DEBUG
+            // draw dirty area
+            {
+                auto bb = m_canvas->m_layers[layer_index].m_dirty_box[plane_index] / (float)m_canvas->m_layers[layer_index].w;
+                glm::vec2 bbmin = xy(bb);
+                glm::vec2 bbsz = zw(bb) - xy(bb);
+                ShaderManager::use(kShader::Color);
+                ShaderManager::u_vec4(kShaderUniform::Col, { 1, 0, 0, 1 });
+                ShaderManager::u_mat4(kShaderUniform::MVP, plane_mvp_z 
+                    * glm::translate(glm::vec3(bbmin * 2.f, 0))
+                    * glm::translate(glm::vec3(-1, -1, 0))
+                    * glm::scale(glm::vec3(bbsz, 1))
+                    * glm::translate(glm::vec3(1, 1, 0))
+                );
+                m_face_plane.draw_stroke();
+            }
+#endif
         }
     }
     if (use_blend)