public GroupViewContext()
        {
            groupListTreeState   = new TreeViewState();
            assetListTreeState   = new TreeViewState();
            groupListHeaderState = GroupListTree.CreateDefaultMultiColumnHeaderState();
            assetListHeaderState = GroupAssetListTree.CreateDefaultMultiColumnHeaderState();

            groupListTreeRect = new Rect(0f, 0f, 300f, 100f);
            assetListTreeRect = new Rect(0f, 0f, 300f, 120f);
        }
        public GroupViewController(GroupViewContext ctx)
        {
            m_ctx = ctx;

            m_groupListTree = new GroupListTree(this, m_ctx.groupListTreeState, m_ctx.groupListHeaderState);
            m_assetListTree = new GroupAssetListTree(this, m_ctx.assetListTreeState, m_ctx.assetListHeaderState);

            m_groupListResize = new ResizeContext();
            m_assetListResize = new ResizeContext();
        }