.TH scrmask 3 "R1c" "Silicon Graphics"
.SH NAME
.I scrmask 
- define a clipping mask for the screen
.SH SYNOPSIS
.nf
.TP \w'FORTRAN\ \ \ 'u
C
.B "scrmask(left, right, bottom, top)"
.B "Screencoord left, right, bottom, top;"
.IP 
.TP \w'FORTRAN\ \ \ 'u
FORTRAN
.B "subroutine scrmas(left, right, bottom, top)"
.B "integer*2 left, right, bottom, top"
.IP 
.TP \w'FORTRAN\ \ \ 'u
Pascal
.B "procedure scrmask(left, right, bottom, top: Screencoord);"
.sp
.SH DESCRIPTION
.I Scrmask
makes it possible to do fine character clipping.  
A call to \f2viewport\f1 sets both the viewport and the screen mask
to the same area, which is defined by the left, right, bottom, and top
boundaries.  A call to \f2scrmask\f1 sets only the screen mask, 
which should be
placed entirely within the viewport.  
Strings that begin outside the viewport will be clipped out; this
is \f2gross clipping\f1.
Strings which
begin inside the
viewport but outside the screen mask
will be clipped to the pixel boundaries
of the screen mask.  This is called \f2fine clipping\f1.
All drawing commands are also clipped to this viewport,
but it is only useful
for characters; gross clipping is sufficient
for all other primitives.
For
an illustration of clipping, see Figure 3.5 of the \f2IRIS Graphics
Library\f1.
.SH "SEE ALSO"
.I getscrmask, viewport