/**
* Override this method to draw your own node.
* The following GL states will be enabled by default:
* - glEnableClientState(GL_VERTEX_ARRAY);
* - glEnableClientState(GL_COLOR_ARRAY);
* - glEnableClientState(GL_TEXTURE_COORD_ARRAY);
* - glEnable(GL_TEXTURE_2D);
* AND YOU SHOULD NOT DISABLE THEM AFTER DRAWING YOUR NODE
* But if you enable any other GL state, you should disable it after drawing your node.
*/
virtual void draw(Renderer *renderer, const Mat4& transform, uint32_t flags);
virtual void draw() final;
第一个函数好理解
第二个函数的final的目的是不能被重载，这也好理解的，我只是觉得奇怪，为什么还要加virtual 关键字。
virtual的目的应该是进行动太绑定…