The UI allows you to control the window system's OpenGL interface with a cross-platform set of pixel format specifiers:
Pixel format attributes

Pixel formats can be requested using these attributes:

pixel-format

<pixel-format> ( world attributes -- pixel-format )

pixel-format-attribute

If a request for a set of pixel format attributes cannot be satisfied, an error is thrown:

invalid-pixel-format-attributes ( world attributes -- * )

Pixel formats are requested as part of opening a window for a world. These generics can be overridden on world subclasses to control pixel format selection:

world-pixel-format-attributes ( world -- attributes )

check-world-pixel-format ( world pixel-format -- )