The X11 font
which I am currently extending to Unicode contains in the C0 range
a number of characters that were also available on DEC VT100 terminals.
I assume xterm uses them to emulate the full VT100 functionality,
which includes a simple blockgraphics capability.
Unfortunately, there are four DEC VT100 block graphics characters that
have apparently no Unicode equivalents. They are each a thin horizontal
line at different heights. H. Peter Anvin <firstname.lastname@example.org> wrote in the
Linux Kernel documentation (/usr/src/linux/Documentation/unicode.txt):
In addition, the following characters not present in Unicode 1.1.4 (at
least, I have not found them!) have been defined; these are used by
the DEC VT graphics map:
U+F800 DEC VT GRAPHICS HORIZONTAL LINE SCAN 1
U+F801 DEC VT GRAPHICS HORIZONTAL LINE SCAN 3
U+F803 DEC VT GRAPHICS HORIZONTAL LINE SCAN 7
U+F804 DEC VT GRAPHICS HORIZONTAL LINE SCAN 9
The DEC VT220 uses a 6x10 character matrix, and these characters form
a smooth progression in the DEC VT graphics character set. I have
omitted the scan 5 line, since it is also used as a block-graphics
character, and hence has been coded as U+2500 FORMS LIGHT HORIZONTAL.
However, I left U+F802 blank should the need arise.
It might be nice to have equivalents for those in Unicode as well
(probably in the U+259X range). Have they just been forgotten or was
there a deliberate decision not to include them?
-- Markus G. Kuhn, Security Group, Computer Lab, Cambridge University, UK email: mkuhn at acm.org, home page: <http://www.cl.cam.ac.uk/~mgk25/>
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