/*
*
Copyright 1989, 1998 The Open Group
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*
* Author: Keith Packard, MIT X Consortium
*/
/* cfb reduced rasterop computations */
#ifdef HAVE_DIX_CONFIG_H
#include <dix-config.h>
#endif
#include <X11/X.h>
#include <X11/Xmd.h>
#include <X11/Xproto.h>
#include "cfb.h"
#include "cfbmskbits.h"
/* A description:
*
* There are four possible operations on each bit in the destination word,
*
* 1 2 3 4
*
* 0 0 0 1 1
* 1 0 1 0 1
*
* On examination of the reduced rop equation (dst = (dst & and) ^ xor),
* these four fall to reduced rops as follows:
*
* and 0 1 1 0
* xor 0 0 1 1
*
* or, (if 'and' is expensive) (dst = (dst | or) ^ xor)
*
* or 1 0 0 1
* xor 1 0 1 0
*
* The trouble with using this later equation is that trivial
* rasterop reduction is more difficult; some common rasterops
* use complicated expressions of xor/and instead of the simple
* ones while other common rasterops are not made any simpler:
*
* GXcopy: *dst = ~xor instead of *dst = xor
* GXand: *dst = *dst & ~or instead of *dst = *dst & and
* GXor: *dst = *dst | or instead of *dst = *dst | xor
* GXxor: *dst = *dst ^ xor instead of *dst = *dst ^ xor
*
* If you're really set on using this second mechanism, the changes
* are pretty simple.
*
* All that remains is to provide a mechanism for computing and/xor values
* based on the raster op and foreground value.
*
* The 16 rops fall as follows, with the associated reduced
* rop and/xor and or/xor values. The values in parenthesis following the
* reduced values gives an equation using the source value for
* the reduced value, and is one of {0, src, ~src, 1} as appropriate.
*
* clear and andReverse copy
* src 0 1 0 1 0 1 0 1
* dst 0 0 0 0 0 0 0 0 1 0 0 1
* 1 0 0 1 0 1 1 0 0 1 0 1
*
* and 0 0 (0) 0 1 (src) 0 1 (src) 0 0 (0)
* xor 0 0 (0) 0 0 (0) 0 1 (src) 0 1 (src)
*
* or 1 1 (1) 1 0 (~src) 1 0 (~src) 1 1 (1)
* xor 1 1 (1) 1 0 (~src) 1 1 (1) 1 0 (~src)
*
* andInverted noop xor or
* src 0 1 0 1 0 1 0 1
* dst 0 0 0 0 0 0 0 0 1 0 0 1
* 1 1 0 1 1 1 1 1 0 1 1 1
*
* and 1 0 (~src) 1 1 (1) 1 1 (1) 1 0 (~src)
* xor 0 0 (0) 0 0 (0) 0 1 (src) 0 1 (src)
*
* or 0 1 (src) 0 0 (0) 0 0 (0) 0 1 (src)
* xor 0 1 (src) 0 0 (0) 0 1 (src) 0 0 (0)
*
* nor equiv invert orReverse
* src 0 1 0 1 0 1 0 1
* dst 0 1 0 0 1 0 0 1 1 0 1 1
* 1 0 0 1 0 1 1 0 0 1 0 1
*
* and 1 0 (~src) 1 1 (1) 1 1 (1) 1 0 (~src)
* xor 1 0 (~src) 1 0 (~src) 1 1 (1) 1 1 (1)
*
* or 0 1 (src) 0 0 (0) 0 0 (0) 0 1 (src)
* xor 1 1 (1) 1 0 (~src) 1 1 (1) 1 0 (~src)
*
* copyInverted orInverted nand set
* src 0 1 0 1 0 1 0 1
* dst 0 1 0 0 1 0 0 1 1 0 1 1
* 1 1 0 1 1 1 1 1 0 1 1 1
*
* and 0 0 (0) 0 1 (src) 0 1 (src) 0 0 (0)
* xor 1 0 (~src) 1 0 (~src) 1 1 (1) 1 1 (1)
*
* or 1 1 (1) 1 0 (~src) 1 0 (~src) 1 1 (1)
* xor 0 1 (src) 0 0 (0) 0 1 (src) 0 0 (0)
*/
int
cfbReduceRasterOp (rop, fg, pm, andp, xorp)
int rop;
CfbBits fg, pm;
CfbBits *andp, *xorp;
{
CfbBits and, xor;
int rrop;
fg = PFILL (fg);
pm = PFILL (pm);
switch (rop)
{
case GXclear:
and = 0;
xor = 0;
break;
case GXand:
and = fg;
xor = 0;
break;
case GXandReverse:
and = fg;
xor = fg;
break;
case GXcopy:
and = 0;
xor = fg;
break;
case GXandInverted:
and = ~fg;
xor = 0;
break;
case GXnoop:
and = ~0;
xor = 0;
break;
case GXxor:
and = ~0;
xor = fg;
break;
case GXor:
and = ~fg;
xor = fg;
break;
case GXnor:
and = ~fg;
xor = ~fg;
break;
case GXequiv:
and = ~0;
xor = ~fg;
break;
case GXinvert:
and = ~0;
xor = ~0;
break;
case GXorReverse:
and = ~fg;
xor = ~0;
break;
case GXcopyInverted:
and = 0;
xor = ~fg;
break;
case GXorInverted:
and = fg;
xor = ~fg;
break;
case GXnand:
and = fg;
xor = ~0;
break;
case GXset:
and = 0;
xor = ~0;
break;
default:
and = xor = 0;
break;
}
and |= ~pm;
xor &= pm;
*andp = and;
*xorp = xor;
/* check for some special cases to reduce computation */
if (and == 0)
rrop = GXcopy;
/* nothing checks for GXnoop
else if (and == ~0 && xor == 0)
rrop = GXnoop;
*/
else if (and == ~0)
rrop = GXxor;
else if (xor == 0)
rrop = GXand;
else if ( (and ^ xor) == ~0) /* fix XBUG 6541 */
rrop = GXor;
else
rrop = GXset; /* rop not reduced */
return rrop;
}
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