Technical: Monospace, clarify double-width codepoint

[Paul Sladen]

In a fixed-width terminal some characters (CJK in particular) are displayed using two (or more) adjacent grid spaces.

Some applications detect whether a font is monospace by looking at the glyph widths and some by looking at the average width entry and other bit flags.

Clarify exactly what is going on and which applications test the mono-ness on which platforms. For example some terminal programs want to load two different fonts, one for single width and one for double width forms:

Markus Kuhn has a table (plus code) based on the Unicode dumps to try and codify which codepoints should be single-width and which should be double-width:

  http://www.cl.cam.ac.uk/~mgk25/ucs/wcwidth.c

See bug 703998, where Ubuntu Mono doesn't show up in KDE's monospace-only font picker until zero-width characters are removed.

[Jonathan Riddell (jr)]

Testing the font from ppa:canonical-ux/walled-garden version 0.70.1-0ubuntu1+phasedbeta1~natty the font shows up in font selection dialogues for general fonts but not in font selection dialogues for monospace fonts (such as in Konsole). It is probably missing a monospace flag somewhere.