T480
Programmer’s Guide
T480 Unicode and Fonts
100-14362
Rev A
Page 209
Font Size and Spacing command interactions
There are interactions between some of the following commands and some of the legacy
font selection commands. These interactions need to be considered when developing a
application for this printer.
This printer uses a font rendering engine that relies on the font to provide character size
and spacing information. Unfortunately, legacy applications assume all characters are
the same and that the character size and spacing is fixed. To force the characters
rendered by the font rendering engine to conform to legacy modes of operation, some
post generation processing is performed to reposition the characters into a fixed size
cell.
The set minimum character height and width ([ESC] + P and [ESC] + p), the set
character spacing ([ESC] + I, [ESC] + i, [ESC] + J and [ESC] + j), the set minimum line
spacing ([ESC] + V and [ESC] + v), and the legacy font select and spacing commands
all interact.
The set minimum character height and width ([ESC] + P and [ESC] + p) commands set
character size but in two different ways. In most systems a character point size refers
only to the line spacing and indirectly to the character height. That is also true. The
vertical character height referenced in these commands refer to the character height
including the white space between lines. The horizontal character width is defined by
the font. Normally only the character height would be specified and the width would be
defined by the font an
d that’s how these commands work if the Width is defined as zero.
If the width is defined as zero this is used as a flag to the printer to generate characters
as defined by the font and use the character width returned by the font. In effect the
vertical point size passed to the font rendering engine is the same as the horizontal
value. The added effect of the width being passed as zero is that any enforced
horizontal spacing is disables. IE the effect of the [ESC] + I, [ESC] + i, [ESC] + J and
[ESC] + j commands are disabled. If the width is not zero, the [ESC] + I, [ESC] + i,
[ESC] + J and [ESC] + j remain in effect and only the resulting character size is changed,
the horizontal spacing is not changed.
The legacy [ESC] ! <n> select the print mode effectively issues a set minimum character
height and width command followed by a set character spacing command without
effecting the pseudo fixed spacing flag.
The pseudo fixed spacing flag is a further complication required for dealing with fonts
that are not truly fixed pitch. In some cases a fixed pitch font will have more that one
character size depending on what the character is used for. This generally only affects
Asian fonts where the ideograms are generally twice as wide as Latin characters. In
fixed spacing mode, the printer will put the rendered character at whatever spacing is
requested even if they don’t fit. If the character is too big, it will overlap the previous and
next character. To allow a fixed pitch operation that deals with small and large fixed
pitch character, the printer has a pseudo-fixed pitch flag that will increase the spacing in
multiples of the requested spacing until it fits.
