[Development] QML TranslationLoader element?

[lars.knoll at nokia.com]

On Jul 31, 2012, at 11:54 AM, ext Jeremy Lainé <jeremy.laine at m4x.org> wrote:

> 
> Le Jul 31, 2012 à 9:34 AM, Alan Alpert a écrit :
> 
>> On Mon, 30 Jul 2012 19:34:23 ext Jeremy Lainé wrote:
>>> I have found QML's network transparency very handy for loading whole UIs
>>> over the network, it makes it possible for instance to have "live updates"
>>> to an application provided all the changes happen on the QML side. However,
>>> once internationalization comes into play, there's a catch: unless I'm
>>> mistaken there's currently no way to load Qt's .qm translations straight
>>> from QML code.
>> 
>> Correct. Currently you need to add additional translation loading inside the 
>> C++ part of your application.
>> 
>>> I was therefore thinking of adding a "TranslationLoader" QML element (along
>>> the lines of FontLoader) which would have the following properties:
>>> 
>>> - QUrl source: the URL to the .qm file
>>> - enumeration status (Null / Ready / Loading / Error): the loader's status
>>> 
>>> Any thoughts on such an addition, or on a better API?
>> 
>> That API looks good. Pretty simple. If the implementation is correspondingly 
>> simple, I think such a type would be a welcome addition to QtQml. All you need 
>> to do is contribute it through gerrit ;) .
>> 
> 
> I have put together a simple implementation which is does the basic job, and am currently experimenting with it in one of my applications. It brought to light a couple of points:
> 
> a/ what is the expected behaviour when a new value is assigned to "source": uninstall the previous translator (my preference) or just add a new translator, keeping the old one?

You should uninstall the old one. For several translators it's better if we use either several TranslationLoader elements or have a special property taking an array of source files.

> b/ if any texts have already been run through qsTr, with my current implementation they are not be re-translated upon successful loading of the translation. Is there a signal or something I can tack onto to trigger a retranslation? For now I have worked around this in my application by only loading the QML files which require translation once the TranslationLoader has finished loading (successfully or with an error).

It'll require a bit of work in in QtQml/QtQuick. Qt sends a QEvent::LanguageChange to all top level windows when a translation gets loaded or removed. So you'll need to add a hook listening for the event in QQuickWindow.
> 
> c/ I noticed that (at least in Qt 4.8) classes such as FontLoader have a special code path (protected by ifdefs) for handling local files. Should I be doing the same, I was under the impression QNetworkAccessManager already had provisions for handling local files?

I think the special code path is there for performance reasons. I'd go through QNAM for now, and once that's properly implemented check whether optimising for local files is worth it.

Cheers,
Lars