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

src/node_panel_quick.cpp

@@ -22,6 +22,11 @@ void NodePanelQuick::init()
     init_controls();
 }
 
+void NodePanelQuick::set_color(glm::vec3 color)
+{
+    static_cast<NodeBorder*>(m_button_color_current->m_children[0].get())->m_color = glm::vec4(color, 1.f);
+}
+
 void NodePanelQuick::init_controls()
 {
     auto s = find<NodeStrokePreview>("quick-brush1");