[Qt-interest] keyPressEvent() confusion with dead keys/accents correctly

[Nikos Chantziaras]

Talking to myself is fun ;-)

I only now realized that there's an event handler called 
inputMethodEvent().  Would have been nice if the docs of keyPressEvent() 
would have mentioned this in the "See also" links.


On 09/29/2010 08:01 PM, Nikos Chantziaras wrote:
> Basically, I ran across this exact same problem:
>
> http://www.qtcentre.org/threads/4653-Handling-of-dead-keys-in-keyPressEvent%28%29
>
>
> I want to capture key presses, including dead keys.
> So for instance, if you press ~ and afterwards n,
> you get ñ (at least on a Spanish keyboard layout).
>
> When I reimplement keyPressEvent() in my widget, I
> get however always the ~ and n separately. I would
> rather get only one keyPressEvent() with the
> complete character.
>
> On his system it was a keyboard layout problem. However, I don't have
> keyboard layout problems and other Qt applications work correctly in
> this regard (I can input accents correctly in Creator for example, or
> any demo app that comes with Qt, or any other Qt app I have installed on
> my system, including the whole of KDE.) So it seems I'm doing it wrong
> in my keyPressEvent()?
>
> My keyPressEvent() receives dead keys. AFAIK, it shouldn't receive them
> in the first place, because when compiling the application for Windows,
> it doesn't. It does only on Linux. Furthermore, if I ignore dead keys
> with something like:
>
> if (e->key() >= Qt::Key_Dead_Grave && e->key() <= Qt::Key_Dead_Horn) {
> QScrollArea::keyPressEvent(e);
> return;
> }
>
> then I get rid of the problem of printing dead keys, but the next key
> event I get still does not contain the correct, accented character in
> its e->text(). It contains the unaccented one.
>
> Turning on key compression with setAttribute(Qt::WA_KeyCompression) does
> not help.
>
> Studying the source code of QTextEdit and its keyPressEvent()
> implementation didn't turn up anything useful either.
>
> My keyPressEvent() implementation can be simplified to this:
>
> if (e->text().isEmpty() || !e->text().at(0).isPrint()
> || (e->key() >= Qt::Key_Dead_Grave
> && e->key() <= Qt::Key_Dead_Horn))
> {
> QScrollArea::keyPressEvent(e);
> return;
> }
>
> qDebug() << e->text()
>
> In this implementation, qDebug will *never* print a "ñ". It's always
> just "n".