add blend mode to layer history

src/node_panel_layer.cpp

@@ -342,6 +342,7 @@ void NodePanelLayer::save_history()
         s.alpha = l->m_opacity;
         s.lock = l->m_alpha_locked;
         s.visible = l->m_visible;
+        s.blend_mode = l->m_blend_mode;
         a->m_layers.push_back(s);
     }
     ActionManager::add(a);
@@ -520,6 +521,7 @@ void ActionLayerChange::undo()
         l->m_opacity = m_layers[i].alpha;
         l->m_alpha_locked = m_layers[i].lock;
         l->m_visible = m_layers[i].visible;
+        l->m_blend_mode = m_layers[i].blend_mode;
     }
     m_panel->update_attributes();
 }
@@ -534,6 +536,7 @@ Action* ActionLayerChange::get_redo()
         s.alpha = l->m_opacity;
         s.lock = l->m_alpha_locked;
         s.visible = l->m_visible;
+        s.blend_mode = l->m_blend_mode;
         a->m_layers.push_back(s);
     }
     return a;

src/node_panel_layer.h

@@ -86,6 +86,7 @@ struct ActionLayerChange : public Action
         bool visible;
         float alpha;
         bool lock;
+        int blend_mode;
     };
     NodePanelLayer* m_panel;
     std::vector<LayerState> m_layers;