
plcalc_world: Calculate world coordinates and
corresponding window index from relative device coordinates 

DESCRIPTION:

	Calculate world coordinates,
	wx and
	wy, and corresponding
	window index
	from relative device coordinates,
	rx and
	ry. 

SYNOPSIS:

plcalc_world(rx, ry, wx, wy, window)

ARGUMENTS:

    rx (PLFLT, input) :    Input relative device coordinate (ranging from
        0. to 1.) for the x coordinate. 

    ry (PLFLT, input) :    Input relative device coordinate (ranging from
        0. to 1.) for the y coordinate. 

    wx (PLFLT *, input) :     Pointer to the returned world coordinate for
        x corresponding to the relative device coordinates rx and ry. 

    wy (PLFLT *, input) :     Pointer to the returned world coordinate for
        y corresponding to the relative device coordinates rx and ry. 

    window (PLINT *, input) :     Pointer to the returned last defined
        window index that corresponds to the input relative device
        coordinates (and the returned world coordinates).  To give some
        background on the window index, for each page the initial window
        index is set to zero, and each time plwind is called within the
        page, world and device coordinates are stored for the window and
        the window index is incremented.  Thus, for a simple page layout
        with non-overlapping viewports and one window per viewport, window
        corresponds to the viewport index (in the order which the
        viewport/windows were created) of the only viewport/window
        corresponding to rx and ry.  However, for more complicated layouts
        with potentially overlapping viewports and possibly more than one
        window (set of world coordinates) per viewport, window and the
        corresponding output world coordinates corresponds to the last
        window created that fulfils the criterion that the relative device
        coordinates are inside it.    Finally, in all cases where the input
        relative device coordinates are not inside any viewport/window,
        then window is set to -1. 
