gdk:cairo-draw-from-gl (cr window source type scale x y width height)

cr -- a cairo:context-t context
window -- a gdk:window object that is rendered for, not necessarily into
source -- an integer for the GL ID of the source buffer
type -- an integer for the type of the source
scale -- an integer for the scale factor that the source buffer is allocated for
x -- an integer for the source x position in source to start copying from in GL coordinates
y -- an integer for the source y position in source to start copying from in GL coordinates
width -- an integer for the width of the region to draw
height -- an integer for the height of the region to draw

This is the main way to draw GL content in GTK. It takes a render buffer ID (type == GL_RENDERBUFFER) or a texture ID (type == GL_TEXTURE) and draws it onto cr with an OVER operation, respecting the current clip. The top left corner of the rectangle specified by x, y, width and height will be drawn at the current (0,0) position of the Cairo context.

This will work for all Cairo contexts, as long as window is realized, but the fallback implementation that reads back the pixels from the buffer may be used in the general case. In the case of direct drawing to a window with no special effects applied to cr it will however use a more efficient approach.

For GL_RENDERBUFFER the code will always fall back to software for buffers with alpha components, so make sure you use GL_TEXTURE if using alpha.

Calling this may change the current GL context.