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

DESCRIPTION:

    This function is used in example 31. 

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

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

    window (PLINT *, output) :      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 fulfills 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. 
