Render a fullscreen quad using the current GL state. The only GL state this modifies is the necessary vertex/index buffers and, if necessary, a Vertex Array Object for drawing a fullscreen quad. Framebuffer state, any shaders, viewport state, etc must be setup by the caller.
Calls filter_texture vfunc with correctly mapped #GstGLMemorys
Transforms input into output using func on through FBO.
Transforms input into output using shader with a FBO.
#GstGLFilter helps to implement simple OpenGL filter elements taking a single input and producing a single output with a #GstGLFramebuffer