Re: A basic question on encoding Latin characters

From: Mark E. Davis (markdavis@ispchannel.com)
Date: Wed Sep 29 1999 - 10:35:21 EDT


Remember, with dead keys the <combining-ring-above> is sent from the terminal *before*
the <a>; this is different than the order that the characters are stored in memory.

Mark

Paul Keinanen wrote:

> On Tue, 28 Sep 1999 21:06:39 -0700 (PDT), "Mark E. Davis"
> <markdavis@ispchannel.com> wrote:
>
> >You misunderstand deadkeys: they reverse the order of typed combining marks. Let
> >me spell it out.
> >
> >User types <combining-ring-above>. Host echos nothing
> >User types <a>.
>
> The terminal sends <a> and <combining-ring-above>, which might be
> received by the host in one packet or a long delay between them.
>
> >Host stores <a-ring>
>
> The host can only store this after a substantial delay or until next
> base character is received.
>
> >and echos the appearance of <a-ring>.
>
> This can happen only after a long delay or after something else is
> typed.
>
> >The host could also use form D, and store the sequence <a><combining-ring-above>,
> >and also echo something with the right appearance (utilizing overlays).
>
> This in fact would be better, since the delay is not needed at the
> host. The host would echo <a> and if <combining-ring-above> is
> received, the a would be erased and replaced with <a-ring>.
> Unfortunately, this does not work for hardcopy terminals.
>
> Paul
>
> >This is
> >what would have to be done for complex scripts, or things like
> ><g><combining-ring-above>, if they are supported by the host.
> >
> >Mark
> >
> >Robert Brady wrote:
> >
> >> On Tue, 28 Sep 1999, Murray Sargent wrote:
> >>
> >> > (The following may well have been mentioned earlier; I haven't followed the
> >> > whole thread). If you enter combining mark sequences using deadkeys, there
> >> > shouldn't be a problem. With deadkeys, nothing is displayed on the terminal
> >> > until the base character is typed and nothing is sent to the pattern-match
> >> > code. When the base character is typed, the corresponding fully composed or
> >> > partially composed character sequence is sent to the terminal and to the
> >> > pattern-match code. Deadkey input methods are usually part of the
> >> > underlying OS, but apps can also implement them fairly easily.
> >>
> >> That doesn't work. Consider a telnet connection. At the end of one TCP
> >> packet, the <a> is placed, but the <combining-ring-above> will not fit, so
> >> it has to go in the next packet.
> >>
> >> Maybe the second packet is delayed for a few seconds, due to network
> >> problems (why is not relevant).
> >>
> >> The app gets the <a> and then a few seconds later gets the
> >> <combining-ring-above>.
> >>
> >> If you can see a way round this (other than abandoning the terminal
> >> metaphor), the linux/utf-8 project would no doubt be happy to hear it. :)
> >>
> >> --
> >> Robert



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