-/* Returns an XImage structure containing an image of the desktop.
- (As a side-effect, that image *may* be painted onto the given Window.)
- This XImage will be 32 bits per pixel, 8 each per R, G, and B, with the
- extra byte set to 0xFF.
+/* Grabs an image of the desktop (or another random image file) and
+ loads tht image into GL's texture memory.
+
+ As a side-effect, that image *may* be painted onto the given Window.
+
+ If mipmap_p is true, then make mipmaps instead of just a single texture.
+
+ If desired_width/height are non-zero, then (if possible) the image
+ will be scaled to fit in that rectangle. If they are 0, then the size
+ of the window is used. These parameters are so that you can hint to
+ the image loader that smaller images are acceptable (if you will never
+ be displaying the texture at 100% magnification, you can get away with
+ smaller textures.)
+
+ Returns the sizes of various things:
+
+ texture_width/height: The size of the texture itself, in pixels.
+ This will often be larger than the grabbed
+ image, since OpenGL sometimes requires texture
+ dimensions to be a power of 2.
+
+ image_width/height: The size of the image: this will usually be the
+ same as the desired_width/height you passed in
+ (but may be the size of the Window instead.)
+
+ geometry: The position in the texture of the image bits.
+ When image files are loaded, they are scaled up
+ to the size of the window, but if the image does
+ not have the same aspect ratio as the window,
+ there will be black bars on the top/bottom or
+ left/right. This geometry specification tells
+ you where the "real" image bits are.
+
+ So, don't use texture coordinates from 0.0 to 1.0. Instead use:
+
+ [0.0 - iw/tw] If you want to display a quad that is the same
+ [0.0 - ih/th] size as the window; or
+
+ [gx/tw - (gx+gw)/tw] If you want to display a quad that is the same
+ [gy/th - (gy+gh)/th] size as the loaded image file.
+
+ Writes to stderr and returns False on error.