fix scroll node, improve animation panel

src/node.h

@@ -49,6 +49,7 @@ enum class kAttribute : uint16_t
     AutoSize = const_hash("autosize"),
     MouseCapture = const_hash("mouse-capture"),
     ScrollColor = const_hash("scroll-color"),
+    ScrollDir   = const_hash("scroll-dir"),
     Multiline = const_hash("multiline"),
     TextAlign = const_hash("text-align"),
     TextVerticalAlign = const_hash("text-vertical-align"),
@@ -116,6 +117,7 @@ public:
 
     glm::mat4 m_proj;
     glm::mat4 m_mvp;
+    glm::mat4 m_mvp_visible;
     bool m_mouse_focus = false;
     bool m_mouse_inside = false;
     bool m_flood_events = false;