DW      TEXTSIZ         ; Determine the height and width of text
                                ; strings in graphics units.

  Input:
     ES:BX      --> ASCII text of the string
     CX         The length (in characters) of the string.

  Return:
     BX         The width of the string in graphics units.
     CX         The height of the string in graphics units.

This function is used to determine the actual physical length and width of
a text string. The current text attributes (set by TEXTSTYLE) are used to
determine the actual dimensions of a string without displaying it. The
application can thereby determine how a specific string will fit and reduce
or increase the font size as required. There is NO graphics output for
this vector. If an error occurs during length calculation, the STAT field
of the Device Status Record should be marked with the device error code.