Atari ST series Technical Reference Manual page 170

*** Change mouse pointer to cross shape
move.l #mdata,INTIN(a5)
dc.w MHide
dc.w MTrans
move.l #mdata+
d c .w MShow
*** determine x and
move.w #304,d6
m o v e .w #184,d7
m o v e .w (a5),d0
do
cmp.w #4,
beg
narrow
6 6
add d ,d
narrow:
0
cmp
#l,d
bne short
add d7,d7
short:
*** set up sprite move
6 0
m o v e .w
d ,d
0
asr.w #l,d
m o v e .w d0,a3
m o v e .w #l,d4
m o v e .w d4,d5
m o v e .w d4,a4
sprite:
3
do
m o v e .w a ,
m o v e .w a4,dl
add.w d 4 , dO
beq xchange
6 0
cmp d ,d
bcs no_xchange
xchange:
eori.w #$FFFE,d4
no_xchange:
d5,dl
add.w
beq ychange
cmp d7,dl
bcs no_ychange
ychange:
eori.w #$FFFE,d5
no_ychange:
m o v e .w d0,a3
dl,a4
m o v e .w
mo v e .w #37,-(sp)
trap #14
. 1 #2
,
ad d q sp
lea savebuf,a
dc.w Undraw
savebuf,a
lea
lea ssave,aO
mo v e .w a3 ,d0
a4 ,dl
mo v e .w
dc.w Draw
*** wait for mouse button press
move.w M0USE_BT(a5),d3
btst #1,d3
beg sprite
*** When right mouse button is pressed,
*** restore mouse pointer to original shape
move.l #psave,INTIN(a5)
dc.w MHide
d c .w MTrans
d c .w MShow
162
CHAPTER 7
* address of mouse data block to INTIN
* hide the pointer
* change its shape
6
,INTIN(a 5)
* make mouse show unconditional
* and show the mouse pointer
screen limits
* right edge - pointer width
* bottom edge - pointer height
* find number of bit planes in display
* is it low-res?
* yes, keep right limit
* no, double screen width
* is it high res?
*
no, keep bottom limit
* yes, double screen height
initial x position = right limit
divided by
save x position
initial x increment = l
initial y increment = l
initial y position =
get x position
get y position
increment x position
if at left, change directions
at right edge?
no, keep going
yes, change direction
increment y position
if at top, change directions
at bottom?
no, keep going
yes, change direction
save x position
save y position
wait for end of vertical blank
2
* use save buffer pointer,
* erase the current sprite
2
* use save buffer pointer,
* use the old mouse pointer shape
* get x position
* y position
* and draw sprite in new position
* check button status
* is right button down?
* no, move sprite
* address of saved mouse data to INTIN
2
.
1