scrbox(3g)scrbox(3g)NAMEscrbox - control the screen box
C SPECIFICATION
void scrbox(arg)
long arg;
PARAMETERS
arg Expects one of the symbolic constants:
SB_RESET: initialize screen box limits and disable the updating of
screen box limits. (default)
SB_TRACK: track scan-converted geometry and characters and update
the scrbox limits accordingly.
SB_HOLD: disable update of screen box limits; hold current values.
DESCRIPTIONscrbox is a dual of the scrmask capability. Rather than limiting drawing
effects to a screen-aligned subregion of the viewport, it tracks the
screen-aligned subregion (screen box) that has been affected. Unlike
scrmask, which defaults to the viewport boundry if not explicitly
enabled, scrbox must be explicitly turned on to be effective.
While enabled (mode SB_TRACK) scrbox maintains leftmost, rightmost,
lowest, and highest window coordinates of all pixels that are scan
converted. Because scrbox operates on the pixels that result from the
scan conversion of points, lines, polygons, and characters; it correctly
handles wide lines, antialiased (smooth) points and lines, and
characters. Because scrbox operation may preceed the framebuffer, scan-
converted pixels may update the screen box regardless of their Z compare,
WID compare, or stencil compare results.
scrbox results are guaranteed to bound the modified framebuffer region,
but they may exceed the bounds of this region.
scrbox results are not affected by calls to clear, zclear, sclear, or
czclear.
When reset, the leftmost and lowest screen box values are set to be
greater than the rightmost and highest values, and the updating of screen
box limits is disabled.
SEE ALSO
getscrbox, scrmask
NOTES
IRIS-4D G, GT, and GTX models, Personal Iris, Impact, and Infinite
Reality, do not support scrbox. Use getgdesc to determine whether scrbox
is supported.
Page 1
