WGL ATI render texture rectangle

There doesn’t seem to be a spec anywhere for the WGL_ATI_render_texture_rectangle extension. Does anyone have the enumerant values?

You mean this enumerant:
#define WGL_TEXTURE_RECTANGLE_ATI 0x21A5

Can you please elaborate more on this? Where did you get the information from? How is this extension used?

It’s from glew.

Search the forum for WGL_TEXTURE_RECTANGLE_ATI, you will find some example.