From: Jukka K. Korpela (email@example.com)
Date: Sun Sep 18 2005 - 01:58:43 CDT
On Sun, 18 Sep 2005, Philippe Verdy wrote:
> From: "Anto'nio Martins-Tuva'lkin" <firstname.lastname@example.org>
>> On 2005.09.17, 19:23, Philippe Verdy <email@example.com> wrote:
>>> keyboard in Widows drivers, by SILENTLY replacing the keys for ASCII
>>> backquote and ASCII tilde by deadkeys for the COMBINING GRAVE ACCENT
>>> and COMBINING TILDE.
>> Are you sure these keys were assigned to U+0300 and U+0303? I'd bet not.
> Don't bet, I am sure they are, but only as *dead keys*, they don't produce a
> character until a second character is entered which determine the final
> character(s) which are output.
I'm not sure I can follow. Are you referring to some recent change that
modified the effect of those keys? It seems to me that you are describing
the usual behavior of "dead keys" (a somewhat misleading, but established
term) but do so in terms of combining characters (which is just wrong).
It's hard to imagine that drivers would have been changed to make a dead
key into a character that produces a combining diacritic. It would
grossly confuse users and could not possibly be a _silent_ change.
One of the basic characteristics of combining marks in Unicode is that
they _follow_ (in the logical order of characters in a data stream) the
character to which they apply (with an exception of a kind for double
diacritics). Dead keys work just the opposite way, so the change would
mean that when people type as they are used to, diacritics would fall on
the wrong letters, or would turn into noncombining marks.
A key is not a character. The symbols in a keycap should associate with
the character(s) that can be typed with the key, but they need not, and
they often do not, describe everything that can be done with the key.
It would probably be better if a dead key's keycap somehow indicated that
it's a dead key and does not immediately produce the character shown in
the keycap. But there are practical difficulties with that.
> Most of the valid sequences generate a precombined character with the
> corresponding diacritic. These dead keys followed by a space don't generate
> the combining character but a spacing diacritic.
That's correct for dead keys. It has nothing to do with combining
diacritic marks, except that both are, in a sense, ways to write
characters with diacritics.
> For invalid
> sequences, on DOS/Windows only, the transformation of a combining tilde dead
> key or the combining grace into a spacing diacritic uses the ASCII symbol
> rather than the other spacing diacritics. But this is just an error
> indicator rather than a valid input.
No, it's the intended behavior. I don't think is an issue of "validity".
Dead keys are an important practical problem. People have difficulties in
learning to use them. People may have used computers for many, many
years without ever realizing how they can use dead keys to type letters
with diacritic marks. They have just wondered why typing "~" or "^"
behaves somewhat oddly, in a delayed manner.
-- Jukka "Yucca" Korpela, http://www.cs.tut.fi/~jkorpela/
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