Atari ST series Technical Reference Manual page 343

+ 116 to +117
line A Copy Raster mode:
Value
Zero Copy Raster Opaque
Nonzero Copy Raster Transparent
+ 118 to +121
Pointer to a routine called by the SeedFill function after each
horizontal line is filled. If this routine returns a value of zero
in register DO, Seed Fill continues filling the next scan line. If
this routine returns a nonzero value in DO, Seed Fill aborts.
At minimum, this vector should point to the routine:
seedabort: sub.l
If this vector is not set before calling Seed Fill, it will proba­
bly point to an illegal address, and Seed Fill will bomb.
The Line A Variable Table
COPYTRAN
Meaning
SEEDABORT
d0,d0 rts
(+$074 to +$075)
( + $076 to +$079)
335