DW      TEXTSTYLE       ; Hardware text style control

  Input:
     AL         Hardware font number
     AH         Hardware font orientation
                0 = Normal,   1 = 90 Degree,   2 = Down
     BX         Desired X Character (size in graphics units)
     CX         Desired Y Character (size in graphics units)

  Return:
     BX         Closest X Character size available (in graphics units)
     CX         Closest Y Character size available (in graphics units)

The TEXTSTYLE vector is used to define the attributes of the hardware font
for output. The parameters affected are the hardware font to be used, the
orientation of the font for output, the desired height and width of the
font output. All subsequent text will be drawn using these attributes.

If the desired size is not supported by the current device, the closest
available match to the desired size should be used. The return value from
this function gives the dimensions of the font (in pixels) that will
actually be used.

For example, if the desired font is 8x10 pixels and the device supports
8x8 and 16x16 fonts, the closest match will be the 8x8. The output of the
function will be BX = 8, and CX = 8.