How to rendering to screen in plugin for ios

I want to render something direct to the screen from plugin.( unity 5.2.3, xcode 7.2 )

And I have tried the latest RenderingPluginExample53 for iOS, but it does not work. I write opengles command( like glclearcolor gl clear ) in extern "C" void UnityRenderEvent(int marker).

These command were invoked, but nothing happend.

Then i write another native function to do the same render, just call the native function from script, the same place RenderingPluginExample53 called GL.IssuePluginEvent. And nothing happend.

I have turned Auto Graphics API to OpenGLES2 only.

So, is there anyone can tell me how to do the rendering , thanks in advance