From: Philippe Verdy (verdy_p@wanadoo.fr)
Date: Tue Apr 01 2008 - 16:39:47 CST
FIRST CONCERN: THE CHOICE OF LATIN LETTER A
Are the letters chosen within the glyph mandarory? I don't think so for such
symbols.
But the choice of letter A in Latin is not very helpful (note that the tiny
comments inserted on the black rounded square box will be unreadable in most
cases, so only the central glyph will remain identifiable).
I'd much prefer to see a Latin letter R, which is distinctive of the Latin
script when compared to Basic Cyrillic, Greek and Coptic (however there's
serious doubt that basic latin will not be supported, so having to display
the lst-resort glyph for characters in the ASCII block is very unlikely; it
is less unlikely for characters in the Latin 1 block (but if needed, the
distinctive character of this block should probably be Latin letter Thorn,
or Latin small letter y with diaeresis). The choice of Omega for Greek is
perfect, as well as the chice of letter IA for Cyrillic, and letter IE for
extended Cyrillic.
SECOND CONCERN: LAST RESORT GLYPHS FOR SURROGATES BLOCKS
Also I'm wondering about the need for last-resort glyphs for the surrogate
blocks (proposed U+E0297?-U+E0299?). Any renderer that would render those
glyphs would not comply to Unicode if it displays them without parsing pairs
as a single codepoint, and then rendering characters, and not code points.
If a document contains isolated or unpaired surrogates, it does not conform
to Unicode for plain text.
So may be its inly use will be for some "visible controls" mode in editors
when all characters in the supplementary planes will be decomposed. But this
mode would not be very helpful as all supplementary characters, including
those supportd in fonts, would be decomposed.
* If some of them are recognized, or the blocks in which they are referenced
is recognized, then the last-rest picture for each recognized supplementary
block will be more helpful.
* If this is for characters that are in still unsupported supplementary
blocks, may be these characters will be shown as pairs of last-resort
glyphs, but my opinion is that the renderer would more probably render some
better last-rest glyph, such as a reversed question mark in a dotted square,
for ALL characters within undefined or unsupported blocks.
* No decomposition into visible surrogates should be made visible to users.
If a document is not conforming to Unicode, every occurrence of an isolated
or unpaired surrogate should be marked distinctly in the text editor using a
glyph that will look more like the one you used in your proposal for illegal
non-characters (i.e. with a black background and the forbidden symbol), and
it should be clearly distinct from the last-resort glyphs used for valid
(assigned or unassigned) character blocks. For me, surrogates are NOT
characters, so if a glyph is ever needed for them, it should clearly be
similar to those used for other NON-CHARACTERS.
> -----Message d'origine-----
> De : unicode-bounce@unicode.org
> [mailto:unicode-bounce@unicode.org] De la part de Michael Everson
> Envoyé : mardi 1 avril 2008 22:04
> À : Unicode Discussion
> Objet : N3412: Last Resort Pictures
>
> Please see
> http://www.evertype.com/standards/iso10646/pdf/n3412-last-resort.pdf
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