Re: A basic question on encoding Latin characters

From: Paul Keinanen (keinanen@sci.fi)
Date: Wed Sep 29 1999 - 04:53:25 EDT


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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