Another "change qt application language at runtime" thread.

maxmotor

But the error happens before this? I have only written:

@template <class T>
class MyTranslation : public QObject
{
T* m_t;

public:
MyTranslation() : m_t(0) {}
~MyTranslation() { if (m_t) m_t->QWidget::removeEventFilter(this); m_t = 0; }
};@

And it gives the error...

BilbonSacquet

I have found some help in internet, seems that your interface (eclipse) not the compiler the problem.

"here some indication":stackoverflow.com/questions/6503551/opencv-type-iplimage-could-not-be-resolved

maxmotor

Thank you :)

I wrote the code in Qt Creator instead of Eclipse, and no errors appear in the MyTranslation.h file.

I am now trying to set up the "MyWidget.h" file.

First of all I can't inherit from Ui::MyWidget. Can this have something to do with MyWidget being a base class for all my ui's?

Secondly, if I leave out Ui::MyWidget, but inherit from MyTranslation<MyWidget>, my ui's seems to get errors, when it comes to the signal and slot connections made.

"reference to 'connect' is ambiguous"

BilbonSacquet

If you couldn't inherits from the Ui::MyWidget you should adapt the code in the handler to find the restranslateUI(), or move the retranslateUI() call in the translationChanged() function.

yes, because you have 2x QObject inheritence. Use at the place the on_awidget_asignal() slots or in this case use QWidget::connect().

maxmotor

I'm sorry, I don't quite understand what you are saying? :(

BilbonSacquet

Sorry, regarding the way I do multiple inheritence, you could find help in the Qt documentation: "Using a Design UI File in Your Application", pay a look to the last chapter:"Automatic Connections".

maxmotor

The link you gave me says

@QMetaObject::connectSlotsByName(this);@

Gives me this error: “'QObject' is an ambiguous base of 'MyWidget'”

But you use QWidget:: Is there a reason for this?

goetz

You inherit twice from QObject:

@
class MyTranslation : public QObject
class MyWidget: public QWidget, public Ui::MyWidget, public MyTranslation<MyWidget>
@

So you inherit from QObject via QWidget (which is a QObject subclass) and via MyTranslation. This is not supported!

maxmotor

BilbonSacquet you must have met this problem then?

BilbonSacquet

It's supported, you should simply take care of the conflict. But we could do it through delegations (I take in consideration all what we say):

@
#include <QtCore/QObject>

template <class T>
class MyTranslator : public QObject
{
T* m_t;

public:
MyTranslator(T* widget)
: m_t(widget)
{
m_t->installEventFilter(this);
}

~MyTranslator() 
{ 
    m_t->removeEventFilter(this); 
}

bool eventFilter(QObject *obj, QEvent *event)
{
    Q_UNUSED(obj);

    if (m_t && event->type() == QEvent::LanguageChange)
    { 
        // not automatally retranslation
        m_t->T:translationChanged();
    }
    return false;
}

};

#include <QtGui/QWidget>

#include <ui_MyWidget.h>
#include <MyTranslator.h>

class MyWidget: public QWidget
{
Q_OBJECT

public:
    MyWidget(QWidget* parent = 0)
    : QWidget(parent), 
      m_translator(this)
    {
        ui.setupUi(this);
    }

    virtual ~MyWidget() {}

    virtual void translationChanged()
    {
        ui.restranslateUi();

        qWarning() << "translator changed";
    }

private:
    MyTranslator<MyWidget> m_translator;
    Ui::MyWidget ui;

};
@

goetz

The "docs of moc":http://doc.qt.nokia.com/4.7/moc.html#multiple-inheritance-requires-qobject-to-be-first state it clearly:

bq. Multiple Inheritance Requires QObject to Be First
If you are using multiple inheritance, moc assumes that the first inherited class is a subclass of QObject. Also, be sure that only the first inherited class is a QObject.
[emphasis by me, Volker]

maxmotor

But now you don't inherit from MyTranslator, in the code you just postet?

BilbonSacquet

Yes, I do both variation (just for you)!

The inherited and the delegated! Both are correct ... just now choose the one you want :).

BilbonSacquet

Even the multiple inherited is correct because (to take the sitation of Volker) the first inherited IS a QObject (QWidget is a QObject)!! :)

goetz

[quote author="BilbonSacquet" date="1321629111"]Even the multiple inherited is correct because (to take the sitation of Volker) the first inherited IS a QObject (QWidget is a QObject)!! :)[/quote]

Don't pick what you want to have and leave out the annoying details that make your design fail!

bq. Also, be sure that only the first inherited class is a QObject.

BilbonSacquet

Both was tested and works! :)

But I give you right, it's never good to multiple inherits QObject. So that's why I rewrite it with a delegation.

But in fact to achieve some automatical translation mechanism (without to hack the current implementation) we need in QObject a callback like in widget for paint event with paintEvent().

goetz

working != officially supported

And the state of "working" may vary between platforms and compilers.

And I don't get the purpose of the template class at all. It calls retranslateUi in the templates argument, so it has to be implemented in all the widgets. Where's the big difference and the coder's savings to implementing changeEvent? On will have to touche every widget class eventually, so why not make it the "standard" way?

BilbonSacquet

You have right not much, I have tried to make something lighter through template (like he suggests) and to have not to write too much code. :)

For the main problem, you should retranslate anyway yourself the 'dynamical' strings.

goetz

There is no significant difference in implementing changeEvent() or translationChanged() - both contain basically the same code regarding the translation (calling ui.retranslateUi() and possibly some manual code). There's a minimal overhead with the event handling in changeEvent().

Just a matter of KISS - no more complex than needed :)

maxmotor

I want to thank you for helping me out! I am very grateful.

I've decided to follow Volkers advice and do it the "official" way. I'm sorry BilbonSacquet - I am really grateful for your work!

I'm trying to follow the example from the link I give in #0 again. I have a few questions though.
How/where is the "language name" added to the actual Ui, enabling the user to choose between available languages? I'm not sure what the component in the example is, but I'm gonna use a qtablewidget to hold my language names. Is this done the same way as in the example?

Thank you so much for your time!