NAME
        TextLength -- Determine raster length of text data.

   SYNOPSIS
        length = TextLength(rp, string, count)
        D0                  A1  A0      D0:16

        WORD TextLength(struct rastport *, strptr, word);

   FUNCTION
        This graphics function determines the length that text data
        would occupy if output to the specified rastport with the
        current attributes.  The length is specified as the number of
        raster dots: to determine what the current position would be
        after a text() using this string, add the length to cp_x
        (cp_y is unchanged by text()).  use the newer textextent() to
        get more information.

   INPUTS
        rp     - a pointer to the rastport which describes where the
                 text attributes reside.
        string - the address of string to determine the length of
        count  - the string length.  If zero, there are no characters
                 in the string.

   RESULTS
        length - the number of pixels in x this text would occupy, not
                 including any negative kerning that may take place at
                 the beginning of the text string, nor taking into
                 account the effects of any clipping that may take
                 place.

   NOTES
        Prior to V36, the result length occupied only the low word of
        d0 and was not sign extended into the high word.

   BUGS
        A length that would overflow single word arithmetic is not
        calculated correctly.

   SEE ALSO
        textextent()  text()  textfit()
        graphics/text.h  graphics/rastport.h