plptex: Write text inside the viewport 

DESCRIPTION:

    Writes text at a specified position and inclination within the
    viewport.  Text is clipped at the viewport boundaries.  The reference
    point of a string lies along a line passing through the string at half
    the height of a capital letter.  The position of the reference point
    along this line is determined by just, the reference point is placed
    at world coordinates (
    x, 
    y) within the viewport.  The inclination of the string is specified in
    terms of differences of world coordinates making it easy to write text
    parallel to a line in a graph. 

SYNOPSIS:

plptex(x, y, dx, dy, just, text)

ARGUMENTS:

    x (PLFLT, input) :      x coordinate of reference point of string. 

    y (PLFLT, input) :      y coordinate of reference point of string. 

    dx (PLFLT, input) :    Together with dy, this specifies the
    inclination of the string.  The baseline of the string is parallel
    to a line joining (
    x, 
    y) to (
    x+
    dx, 
    y+
    dy). 

    dy (PLFLT, input) :    Together with dx, this specifies the
    inclination of the string. 

    just (PLFLT, input) :    Specifies the position of the string relative
    to its reference point.  If just=0, the reference point is at the
    left and if just=1, it is at the right of the string.  Other
    values of just give intermediate justifications. 

    text (const char *, input) :    The string to be written out.