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早期freebsd实现

	"cfb" Beta version - 8 July 1987

Written by:

	Stuart Marks		Sun Microsystems

With help from:

	David Rosenthal		Sun Microsystems
	Jack Palevich		Hewlett-Packard
	Bob Leichner		Hewlett-Packard

This directory contains an analogue of "mfb" for memory color framebuffers.
It can be configured to support a number of different devices:

	-	They must be organised as packed pixels,  not planewise.
	-	They must have fewer than 32 bits per pixel.

The code has been tested only on displays with a pixel size of 8 bits,
both with all 8 planes implemented (Sun) and less than 8 planes implemented (HP).
As distributed,  it is set up for 8-bit pixels with all 8 planes implemented.
If your display is different,  see maskbits.h.

The code is intended to be highly portable,  and to use as much as possible of the
"mi" code.  As a result,  it is very slow.  But we believe it should be very
easy to port.  We believe that the code only ever accesses the framebuffer 32 bits
wide at 4-byte aligned addresses.

As delivered,  the code supports a PseudoColor visual.  By defining STATIC_COLOR,
you can configure it (and the .../sun directory) to support a StaticColor visual
instead.  This has proved useful in testing the server.