Atari ST series - Page 157

Line A Routines
turns a zero in register DO, Seed Fill keeps going, but if it
returns a nonzero value, Seed Fill aborts. Since Seed Fill will
JSR through the SEED ABORT vector at the end of each scan
line, you must place a pointer to subroutine in this vector, or
Seed Fill will bomb after the first line. At a minimum, this
subroutine should clear register DO and execute an RTS in
struction.
Program 7-3 demonstrates all four of the line A filled
shape functions.
Program 7-3. FILLDRAW.S
* FILLDRAW.S — Demonstrates the use of the line A *
* filled shape functions. *
* *
************************************************************
*** variable table offsets
CUR_WORK = -464
CONTRL = $04
INTIN = $08
PTSIN = $0C
COLBITO = $18
COLBIT1 = $1A
C0LBIT2 = $1C
COLBIT3 = $1E
LNMASK = $22
WMODE = $24
XI = $26
Y1 = $28
X2 = $2A
V5 s
PATPTR = $2E
PATMSK = $32
MFILL = $34
CLIP = $36
XMINCL = $38
YMINCL = $3A
XMAXCL = $3C
YMAXCL = $3E
SEEDABORT = $76
*** Function Equates
Init = $a000
Aline = $a003
Hline = $a004
RectFill = $a005
PolyFill = $a006
SeedFill = $a00f
*** program starts here
.text
dc.w Init
*
move.1 a0,a5
*
*
move.w #0,COLBITO(a5)
*
move.w
#1,COLBIT1(a5)
*
move.w
#0,COLBIT2(a5)
*
move.w #0,COLBIT3(a5)
*
move.w
#0,WMODE(a5)
*
move.1
#love,PATPTR(a5)
*
move.w #15,PATMSK(a5)
*
move.w
#0,MFILL(a5)
*
move.w #l,CLIP(a5)
*
move.w #0,XMINCL(a5)
*
get base address of variable table
save base address...
because PolyFill destroys AO
color bits set to register
0010
or color 2 (green)
replace mode
set fill pattern
and length of fill pattern
multiplane fill off
clipping on
set clip rectangle..
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