Atari ST series - Page 153

Line A Routines
Table 7-2. Input Values for Filled Rectangle Function (continued)
Offset Name Offset
Description
WMODE
$24
Writing mode
XI $26
Starting x coordinate
Yl $28
Starting y coordinate
X2
$2A
Ending x coordinate
Y2 $2C
Ending y coordinate
PATPTR $2E
Pointer to fill pattern array
PATMSK
$32
Pattern index (length - 1)
MFILL $34
Multi-color fill pattern flag (zero = single
plane, nonzero = multiplane)
CLIP $36
Clipping flag (zero = off, nonzero = on)
XMINCL $38
Coordinate of left side of clip rectangle
YMINCL
$3A
Coordinate of top of clip rectangle
XMAXCL $3C
Coordinate of right side of clip rectangle
YMAXCL
$3E
Coordinate of bottom of clip rectangle
These inputs are the same for Horizontal Line, with the
addition of the clipping rectangle variables. XMINCL,
YMINCL, XMAXCL, and YMAXCL are used to designate the
borders of the clipping rectangle. The CLIP variable is used
to indicate whether the clipping actually takes place. If CLIP
is set to 0, clipping is turned off, and the rectangle desig
nated by the other four variables is ignored. If CLIP is not 0,
clipping is turned on, and only the portion of the filled rec
tangle that lies within the clipping rectangle will be drawn.
A similar call to Filled Rectangle is Filled Polygon
($A006). Instead of drawing a filled box, this call draws a
filled shape with an arbitrary number of sides. It does this by
drawing a series of filled horizontal lines of unequal size.
The input values used by Filled Polygon are shown in Table
7-3.
Table 7-3. Input Values Used by Filled Polygon
Description
Pointer to a word array. The second
member of the array, CONTRL[l], contains
the number of polygon vertices
Pointer to a word array. This array
contains polygon vertex pairs in the format
(xl, yl), (x2, y2), and so on.
Bit value for color plane 0
Bit value for color plane 1
Bit value for color plane 2
Offset Name
Offset
CONTRL $04
PTSIN $0C
COLBITO $18
COLBIT1 $1A
COLBIT2 $1C
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