use mutex to avoid window destroy deadlock, fix vertical slider to increase value upward

src/node_panel_quick.h

@@ -23,6 +23,7 @@ public:
     virtual Node* clone_instantiate() const override;
     virtual void clone_finalize(Node* dest) const override;
     virtual void init() override;
+    void set_color(glm::vec3 color);
 private:
     void init_controls();
     void handle_button_color_click(Node* target);