collapseos/blk/553

# 6/8 bit columns and smaller fonts

If your glyphs, including padding, are 6 or 8 pixels wide,
you're in luck because pushing them to the LCD can be done in a
very efficient manner.  Unfortunately, this makes the LCD
unsuitable for a Collapse OS shell: 6 pixels per glyph gives us
only 16 characters per line, which is hardly usable.

This is why we have this buffering system. How it works is that
we're always in 8-bit mode and we hold the whole area (8 pixels
wide by FNT_HEIGHT high) in memory. When we want to put a glyph
to screen, we first read the contents of that area, then add
our new glyph, offsetted and masked, to that buffer, then push
the buffer back to the LCD. If the glyph is split, move to the
next area and finish the job.
                                                        (cont.)