page@swan.ulowell.edu (Bob Page) (11/11/88)
Submitted-by: rucklidg@svax.cs.cornell.edu (William Rucklidge)
Posting-number: Volume 2, Issue 60
Archive-name: graphics/flip.1
Here's a screen hack I came up with a while ago.
[binary included too, it's small. ..Bob]
# This is a shell archive.
# Remove everything above and including the cut line.
# Then run the rest of the file through sh.
#----cut here-----cut here-----cut here-----cut here----#
#!/bin/sh
# shar: Shell Archiver
# Run the following text with /bin/sh to create:
# README
# flip.c
# flip.uu
# This archive created: Thu Nov 10 16:45:22 1988
cat << \SHAR_EOF > README
Here's Yet Another Screen Hack I wrote in a moment of boredom.
Type "flip", and observe. Try typing a few other commands, like "list".
Type "flip" again to restore (or do anything which affects screen
ordering/position (e.g. Left-Amiga-N)).
For some reason or other this doesn't work reliably if you have more
than the Workbench screen open. It won't crash the machine, but it won't
have the desired effect.
- William Rucklidge
rucklidg@svax.cs.cornell.edu
SHAR_EOF
cat << \SHAR_EOF > flip.c
/*
* flip.c - yet another screen hack
*
* William Rucklidge rucklidg@svax.cs.cornell.edu
*
* This code is released into the public domain. What's the point in
* copyrighting something like this, anyway?
*
* Thanks to jimm, for dcop.
*
* This will work on simple workbench screens. There seems to be some problem
* when more than one screen is open: GfxBase->ActiView doesn't seem to contain
* the right information (the copper lists and the View don't match). I'm
* probably just not looking in the right place, though.
*
* This makes some assumptions about the copper list: that the modulo registers
* are loaded before the bitplane data pointers, that the bitplane data pointers
* are loaded in successive instructions, high then low, and that the copper
* list being mangled is that of a fully displayed screen (not a window into a
* larger bitmap). These assumptions are all true for automatically generated
* copper lists.
*
* This does seem to work with vscreen'd and morerowed Workbench screen.
*
*/
#include <graphics/gfxbase.h>
#include <graphics/view.h>
#include <graphics/copper.h>
/* The codes for a few copper instructions */
#define MOVEBPL1MOD 0x0108
#define MOVEBPL2MOD 0x010A
#define MOVEBPL1PT 0x00E0
#define MAXPLANES 6
#define PTSKIP 4
#define MOVEBPLPT(x) (MOVEBPL1PT + ((x) - 1) * PTSKIP)
extern void *OpenLibrary(), CloseLibrary(), Forbid(), Permit();
struct GfxBase *GfxBase;
typedef int boolean;
#undef FALSE
#undef TRUE
#define FALSE 0
#define TRUE 1
void
mangleCprList(list, isLOF, bpl, vy)
struct cprlist *list; /* A copper list to be mangled. */
boolean isLOF; /* Is this a LOF coppper list? */
unsigned short bpl; /* The number of bytes per line */
unsigned short vy; /* The number of lines */
{
register short *cp, inst;
char *oldbplpt;
char *newbplpt;
register int i;
long offset;
boolean wasflipped = FALSE;
if (!list) {
return;
}
for (i = list->MaxCount, cp = (short *)list->start;
i > 0;
i--, cp += 2) {
inst = *cp;
if ((inst == MOVEBPL1MOD) || (inst == MOVEBPL2MOD)) {
/* Mangle the modulus */
if (*(cp + 1) < 0) {
wasflipped = TRUE;
}
*(cp + 1) = - (bpl << 1) - *(cp + 1);
}
else if ((inst >= MOVEBPLPT(1)) && (inst < MOVEBPLPT(MAXPLANES + 1))
&& (!(inst & 3))) {
/* This is a load bitplane address register instruction.
* Make sure that this instruction is followed by one to
* load the other half of the register
*/
if ((*(cp + 2) == inst + 2) && (i > 1)) {
/* Mangle the bitplane address */
/* Pick out the address from the operands of the instructions */
oldbplpt = (char *)((((long)*(cp + 1)) << 16) +
(unsigned short)(*(cp + 3)));
offset = (vy - 1) * (long)bpl +
(isLOF ? 0 : -((short)bpl << 1));
if (!wasflipped) {
newbplpt = oldbplpt + offset;
}
else {
newbplpt = oldbplpt - offset;
}
/* Install the new address */
*(cp + 1) = (long)newbplpt >> 16;
*(cp + 3) = (long)newbplpt & 0xffff;
}
}
}
}
int
main()
{
unsigned short bpl, vy;
GfxBase = OpenLibrary("graphics.library", 0L);
/* We don't want anyone rebuilding the copper lists while we mangle them */
Forbid();
/* Get bytes per line and screen height */
bpl = ((GfxBase->ActiView->ViewPort->DWidth) >> 3) & ~1;
vy = GfxBase->ActiView->ViewPort->DHeight;
mangleCprList(GfxBase->ActiView->LOFCprList, TRUE, bpl, vy);
mangleCprList(GfxBase->ActiView->SHFCprList, FALSE, bpl, vy);
Permit();
CloseLibrary(GfxBase);
return(0);
}
SHAR_EOF
cat << \SHAR_EOF > flip.uu
begin 644 flip
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M[O^R```#[`````$````!```")@````````/R```#Z@````$`%``````#\@``D
*`^L````!```#\@$`E
``
end
size 2260
SHAR_EOF
# End of shell archive
exit 0
--
Bob Page, U of Lowell CS Dept. page@swan.ulowell.edu ulowell!page
Have five nice days.