Atari ST series - Page 169

Line A Routines
nal value afterwards). The current x and y positions of the
mouse pointer are stored in GCURX (offset — 602) and
GCURY (offset —600). The mouse button status is contained
in MOUSE __ BT (-596). Bit 0 covers the left button status,
while bit one covers the right button. A 1 bit indicates that
the button is currently pressed.
Program 7-5 demonstrates the use of both sprites and
the mouse pointer. It copies the pointer arrow shape to a
sprite, and bounces the sprite around the screen until you
press the right mouse button. It also changes the shape of
the mouse pointer to a cross and changes it back when you
press the button.
Program 7-5. MOUSPRIT.S
* *
* MOUSPRIT.S — Demonstrates use of the line A *
* mouse pointer and sprite calls. *
* *
★ *
*** Variable table offsets
MOUSE_BT = -596 * offset for mouse button status variable
M_POS_HX = -856 * offset for start of mouse pointer sprite data
INTIN = $08
*** Function Equates
Init = $a000
MShow = $a009
MHide = $a00a
MTrans = $a00b
Undraw = $aOOc
Draw = $a00d
*** Program starts here
.text
dc.w Init * get base address of variable table
move.l a0,a5 * save base address,
* * in case other calls destroy AO
*** save old mouse pointer sprite data
*** both in sprite format, and pointer format
*** (pointers use separate data planes, sprites interleave them)
move.w
#4,dO
*
save 5 words of mouse data
lea
M_POS_HX(a5),al
*
get starting address to save
lea
psave,a2
*
start address of pointer save area
lea
ssave,a4
*
& start address of sprite save area
savhead:
move.w
(al),(a4)+
*
move 5 word header to both buffers
move.w
(al)+,(a2)+
*
(header is same for sprites & pointers)
dbra do,savhead
move.w #15,dO
dbra
psave+42,a3
lea
savdata:
move (al),(a4)+
move.w (al)+,(a2)+
move.w (al),(a4)+
move.w (al)+,(a3)+
dO,savdata
* save 32 words of mouse data
* even words in sprite format
* even words in pointer format
* odd words in sprite format
* odd words in pointer format
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