Combining Marks and Keyboard Input on GUI systems (was: Re: A basic question on encoding Latin characters)

From: Karl Pentzlin (karl-pentzlin@acssoft.de)
Date: Tue Oct 05 1999 - 11:49:01 EDT


----- Original Message -----
From: Frank da Cruz <fdc@watsun.cc.columbia.edu>
Subject: RE: A basic question on encoding Latin characters

> Even in the GUI world, as many have pointed out already, we commonly see
> single-letter shortcuts in dropdown menus. Suppose a German application
> has:
>
> [÷]ffnen
> [O]rdnen
>
> and the application is reading characters (not keycodes). The application
> either waits forever for a combining diaeresis that will not come, or it
> gets a false positive on the 'O' when in fact '÷' was typed.

This situation can be overcome with ease. Compare it with the distinction of
a single mouse click with a double click - if the second click does not
happen within a specific time (e.g. 0.5 seconds), the software can safely
assume a single click. As the "÷" input choice makes sense only if the
keyboard has an ÷ key (German keybords have one commonly), the application
has to wait only the time the system needs for the keyboard decoding - i.e.
on modern systems less than 10 milliseconds. [BTW, on Microsoft Windows
systems the software has to wait to the "key released" message anyway - thus
there would be an unambiguous message sequence "key-pressed - key-O -
key-diaresis/umlaut - key-released" without the need for any timeout (as
long as the precomposed letter is not used anyway)]. If the user hits the O
key instead, he wants to "[O]rdnen" - there is no need to wait seconds
whether he types in a combining diaresis/umlaut later somehow. If he uses a
keyboard with a "diaresis/umlaut dead key", he will type it *before* the O
anyway (to indicate to the Unicode-conformant software that it has to store
the dead key and to append the code later to the result of the following
keyboard input).

Regards
Karl Pentzlin
AC&S Analysis Consulting & Software GmbH
MŁnchen, Germany



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