Atari ST series Technical Reference Manual page 157

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 —
*
*
************************************************************
*** 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
mo v e .1 a0,a5
m o v e .w #0,COLBITO(a5)
move.w
#1,COLBIT1(a5)
move.w #0,COLBIT2(a5)
move.w #0,COLBIT3(a5)
move.w #0,WMODE(a5)
m o v e .1 #love,PATPTR(a5)
move.w #15,PATMSK(a5)
m o v e .w #0,MFILL(a5)
m o v e .w #l,CLIP(a5)
m o v e .w #0,XMINCL(a5)
Line A Routines
Demonstrates the use of the line A
filled shape functions.
*
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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