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# Copyright(c) 1986 Association of Universities for Research in Astronomy Inc.
include <mach.h>
include <gio.h>
include <gki.h>
include "gtr.h"
# GTR_PTRAN -- Set the workstation transformation. The workstation
# transformation is automatically zeroed whenever the screen is cleared
# or when a workstation is opened.
procedure gtr_ptran (stream, x1, x2, y1, y2)
int stream # graphics stream to be set
real x1, x2 # range of workstation viewport in X
real y1, y2 # range of workstation viewport in Y
pointer tr
real tol, min_width, dx, dy
real cx1, cx2, cy1, cy2
include "gtr.com"
begin
tr = trdes[stream]
tol = 5.0 * EPSILON
if (abs(x1) < tol && abs (x2 - 1.0) < tol &&
abs(y1) < tol && abs (y2 - 1.0) < tol) {
wstranset = NO
} else {
# Save viewport.
vx1 = x1
vx2 = x2
vy1 = y1
vy2 = y2
# Clip viewport at NDC boundary.
cx1 = max (0., min (1., x1))
cx2 = max (0., min (1., x2))
cy1 = max (0., min (1., y1))
cy2 = max (0., min (1., y2))
# Make sure the viewport does not have a zero extent in either
# axis after clipping.
min_width = 1E-4
if (cx2 - cx1 < min_width)
cx2 = cx1 + min_width
if (cy2 - cy1 < min_width)
cy2 = cy1 + min_width
# Set clipping viewport in input GKI space.
mx1 = nint (cx1 * GKI_MAXNDC)
mx2 = nint (cx2 * GKI_MAXNDC)
my1 = nint (cy1 * GKI_MAXNDC)
my2 = nint (cy2 * GKI_MAXNDC)
# Set transformation upon the clipped GKI coordinates.
dx = max (min_width, (x2 - x1))
dy = max (min_width, (y2 - y1))
xorigin = (cx1 - x1) / dx * GKI_MAXNDC
yorigin = (cy1 - y1) / dy * GKI_MAXNDC
xscale = 1. / dx
yscale = 1. / dy
wstranset = YES
}
# Clear the scratch buffer whenever the workstation viewport is
# changed.
TR_OPSB(tr) = TR_SCRATCHBUF(tr)
end
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