PGPLOT Module: PGQVSZ -- inquire size of view surface

REAL X1, X2, Y1, Y2

This routine returns the dimensions of the view surface (the maximum
plottable area) of the currently selected graphics device, in
a variety of units. The size of the view surface is device-dependent
and is established when the graphics device is opened. On some
devices, it can be changed by calling PGPAP before starting a new
page with PGPAGE. On some devices, the size can be changed (e.g.,
by a workstation window manager) outside PGPLOT, and PGPLOT detects
the change when PGPAGE is used. Call this routine after PGPAGE to
find the current size.

Note 1: the width and the height of the view surface in normalized
device coordinates are both always equal to 1.0.

Note 2: when the device is divided into panels (see PGSUBP), the
view surface is a single panel.

UNITS (input) : 0,1,2,3 for output in normalized device coords,
inches, mm, or device units (pixels)
X1 (output) : always returns 0.0
X2 (output) : width of view surface
Y1 (output) : always returns 0.0
Y2 (output) : height of view surface