Support of 1 bit visuals from SGI's X server.

[Phil Karlton]

The X protocol does require that all servers support 1 bit deep PIXMAPs
(often referred to as a bitmap in the X community as well as elsewhere).
PIXMAPs are like WINDOWs in the sense that they are DRAWABLEs meaning
that any of the X rendering calls will work to any of them.

There is no requirement that there be a 1 bit deep visual. In fact, I
know of no server that supports both 1 bit deep visuals and deeper
visuals to the primary frame buffer. It is legal for a server to do so,
and I am sure there must be an implementation that does it.

The Irix 4.0 server will have an optimised path for doing a CopyPlane
from a bitmap to an appropriate depth window on the screen. For some of
our hardware, this operation will be limited by the data paths to the
frame buffer. There is no reason why CopyPlane from a bitmap should run
any slower than CopyArea from a deep PIXMAP. CopyArea from WINDOW to
WINDOW might entail crossing the frame buffer data paths twice.

PK