Dynamic translation (was: How to get QApplication pointer)

[Gopala Krishna]

Hi to all!

I have an QApplication object in which QTranslator is installed. It works perferctly. But now I have a problem. I have a "grandchild" qwidget that holds language selection QPushButton subclassed objects. How do I launch QApplication::loadTranslator from this window??

Use qApp
qApp->loadTranslator();

[MarkoSan]

Hmm, this does not work:

void CLanguageSelectorWidget::translateSlovene()
{
    m_Translator.load("translations/eROSystem_client_SL");    // loads translator
    //QApplication::installTranslator(&m_Translator);    // installs it
    qApp->installTranslator(&m_Translator);    // installs it
    emit accept();    // closes window
}

void CLanguageSelectorWidget::translateSlovene()
{
    m_Translator.load("translations/eROSystem_client_SL");    // loads translator
    //QApplication::installTranslator(&m_Translator);    // installs it
    qApp->installTranslator(&m_Translator);    // installs it
    emit accept();    // closes window
}

To copy to clipboard, switch view to plain text mode 

Why not???

In main.cpp there is a very similar code that works:

// translator setup
    QTranslator qtTranslator;
    qtTranslator.load("translations/eROSystem_client_SL");
    a.installTranslator(&qtTranslator);

// translator setup
    QTranslator qtTranslator;
    qtTranslator.load("translations/eROSystem_client_SL");
    a.installTranslator(&qtTranslator);

To copy to clipboard, switch view to plain text mode 

Why the upper code chunk does not work?? Signals/Slots are ok, I've checked.

[jpn]

In main() the QTranslator object remains alive because QApplication::exec() blocks until the application quits. Is CLanguageSelectorWidget allocated on the stack? The translator object goes out of scope as soon as CLanguageSelectorWidget is destructed.

[MarkoSan]

How come, if m_Translator is defined in its header file:

#ifndef CLANGUAGESELECTORWIDGET_H_
#define CLANGUAGESELECTORWIDGET_H_
 
/*!
 * \class CLanguageSelectorWidget
 * \author VSistemi Marko Frelih s.p.
 * \version 1.0
 * \date January 2007
 * \brief This Qt based class represents a language selector widget, which constist of number of
 *     CFlagButton objects.
 * \details version 1.00 (revision 84): basic functionality
*/
 
// qt includes
#include <QDialog>
#include <QHBoxLayout>
#include <QVBoxLayout>
#include <QList>
#include <QFont>
#include <QPalette>
#include <QTranslator>
#include <QApplication>
 
class QWidget;    // forward declaration
 
// custom includes
#include "CFlagButton.h"
 
class CLanguageSelectorWidget : public QDialog
{
    Q_OBJECT
 
public:
    CLanguageSelectorWidget(QWidget* pParent);
    ~CLanguageSelectorWidget();
    inline QPointer<QHBoxLayout> langaugeButtonsLayout() { return m_pLanguageButtonsLayout; };
    inline QPointer<QVBoxLayout> mainLayout() { return m_pMainLayout; };
    //inline QList<CFlagButton> languageButtonsList() { return mLanguageButtonsList; };
    inline QPalette widgetPalette() { return m_WidgetPalette; };
    inline QPointer<QPushButton> sloLangButton() { return m_pSloLangButton; };
    inline QPointer<QPushButton> ukLangButton() { return m_pUKLangButton; };
    inline QPointer<QPushButton> deuLangButton() { return m_pDeuLangButton; };
    inline QPointer<QPushButton> itaLangButton() { return m_pItaLangButton; };
 
public:
    // TODO: this member should be private
    //QList<CFlagButton> mLanguageButtonsList;    // language buttons list
 
private:
    QPointer<QHBoxLayout> m_pLanguageButtonsLayout;    // horizontal layout
    QPointer<QVBoxLayout> m_pMainLayout;    // main layouts
    QPointer<QPushButton> m_pSloLangButton;    // slo lang
    QPointer<QPushButton> m_pUKLangButton;    // eng lang
    QPointer<QPushButton> m_pDeuLangButton;    // deu lang
    QPointer<QPushButton> m_pItaLangButton;    // ita lang
    QPalette m_WidgetPalette;    // widget palette
    QTranslator m_Translator;    // application translator
 
private slots:
    void translateSlovene();    // launches slovenian translation
    void translateEnglish();    // launches english translation
    void translateDeutsch();    // launches german translation
    void translateItaliano();    // launches italian translation
};
 
#endif /*CLANGUAGESELECTORWIDGET_H_*/

#ifndef CLANGUAGESELECTORWIDGET_H_
#define CLANGUAGESELECTORWIDGET_H_

/*!
 * \class CLanguageSelectorWidget
 * \author VSistemi Marko Frelih s.p.
 * \version 1.0
 * \date January 2007
 * \brief This Qt based class represents a language selector widget, which constist of number of
 *     CFlagButton objects.
 * \details version 1.00 (revision 84): basic functionality
*/

// qt includes
#include <QDialog>
#include <QHBoxLayout>
#include <QVBoxLayout>
#include <QList>
#include <QFont>
#include <QPalette>
#include <QTranslator>
#include <QApplication>

class QWidget;    // forward declaration

// custom includes
#include "CFlagButton.h"

class CLanguageSelectorWidget : public QDialog
{
    Q_OBJECT
    
public:
    CLanguageSelectorWidget(QWidget* pParent);
    ~CLanguageSelectorWidget();
    inline QPointer<QHBoxLayout> langaugeButtonsLayout() { return m_pLanguageButtonsLayout; };
    inline QPointer<QVBoxLayout> mainLayout() { return m_pMainLayout; };
    //inline QList<CFlagButton> languageButtonsList() { return mLanguageButtonsList; };
    inline QPalette widgetPalette() { return m_WidgetPalette; };
    inline QPointer<QPushButton> sloLangButton() { return m_pSloLangButton; };
    inline QPointer<QPushButton> ukLangButton() { return m_pUKLangButton; };
    inline QPointer<QPushButton> deuLangButton() { return m_pDeuLangButton; };
    inline QPointer<QPushButton> itaLangButton() { return m_pItaLangButton; };

public:
    // TODO: this member should be private
    //QList<CFlagButton> mLanguageButtonsList;    // language buttons list

private:
    QPointer<QHBoxLayout> m_pLanguageButtonsLayout;    // horizontal layout
    QPointer<QVBoxLayout> m_pMainLayout;    // main layouts
    QPointer<QPushButton> m_pSloLangButton;    // slo lang
    QPointer<QPushButton> m_pUKLangButton;    // eng lang
    QPointer<QPushButton> m_pDeuLangButton;    // deu lang
    QPointer<QPushButton> m_pItaLangButton;    // ita lang
    QPalette m_WidgetPalette;    // widget palette
    QTranslator m_Translator;    // application translator

private slots:
    void translateSlovene();    // launches slovenian translation
    void translateEnglish();    // launches english translation
    void translateDeutsch();    // launches german translation
    void translateItaliano();    // launches italian translation
};

#endif /*CLANGUAGESELECTORWIDGET_H_*/

To copy to clipboard, switch view to plain text mode 

[jpn]

Where do you show/exec CLanguageSelectorWidget? Consider following code:

{
    CLanguageSelectorWidget dialog(this);
    if (dialog.exec() == QDialog::Accepted)
    {
    }
} // the translator gets destructed here together with CLanguageSelectorWidget

{
    CLanguageSelectorWidget dialog(this);
    if (dialog.exec() == QDialog::Accepted)
    {
    }
} // the translator gets destructed here together with CLanguageSelectorWidget

To copy to clipboard, switch view to plain text mode 

[MarkoSan]

So, what do you suggest, how should I recode?

[jpn]

Allocate the translator on the heap. In other words, create the translator with keyword "new". It must remain alive after the dialog gets destructed, right?

[MarkoSan]

Yes, you are right. God damn, I've forgot the basics ... I've allocated it, but same result. I think object gets destructed again after leaving QDialog:

m_pTranslator=new QTranslator(this);    // creats new translator
    Q_CHECK_PTR(m_pTranslator);    // checks creation
    m_pTranslator->load("translations/eROSystem_client_ITA");    // loads translator
    //QApplication::installTranslator(&m_Translator);    // installs it
    qApp->installTranslator(m_pTranslator);    // installs it
    emit accept();    // closes window

m_pTranslator=new QTranslator(this);    // creats new translator
    Q_CHECK_PTR(m_pTranslator);    // checks creation
    m_pTranslator->load("translations/eROSystem_client_ITA");    // loads translator
    //QApplication::installTranslator(&m_Translator);    // installs it
    qApp->installTranslator(m_pTranslator);    // installs it
    emit accept();    // closes window

To copy to clipboard, switch view to plain text mode 

Am I right?

[jpn]

Don't pass "this" as its parent. Every QObject will automatically delete its children. Here, the dialog will delete the translator. Try passing for example "qApp" as parent instead.

[MarkoSan]

I did, still no result. Is it possible the path to translator file is corrupted??? Is it ok to use "/" in path under windows instead of "\'

[jpn]

I did, still no result. Is it possible the path to translator file is corrupted???

QTranslator::load() returns true if the translation is successfully loaded; otherwise returns false. So check the return value!

Is it ok to use "/" in path under windows instead of "\'

Yes, it's ok. Qt will translate your paths to conform to the underlying operating system.

[MarkoSan]

Here is the code:

m_pTranslator=new QTranslator(qApp);    // creats new translator
    Q_CHECK_PTR(m_pTranslator);    // checks creation
    if(m_pTranslator->load("translations/eROSystem_client_ITA"))    // loads translator
    {
        //QApplication::installTranslator(&m_Translator);    // installs it
        qApp->installTranslator(m_pTranslator);    // installs it
        emit accept();    // closes window, success    
    } else {
        emit reject();    // failure
    }

m_pTranslator=new QTranslator(qApp);    // creats new translator
    Q_CHECK_PTR(m_pTranslator);    // checks creation
    if(m_pTranslator->load("translations/eROSystem_client_ITA"))    // loads translator
    {
        //QApplication::installTranslator(&m_Translator);    // installs it
        qApp->installTranslator(m_pTranslator);    // installs it
        emit accept();    // closes window, success    
    } else {
        emit reject();    // failure
    }

To copy to clipboard, switch view to plain text mode 

Every language button succesfully loads translator. But still no result!!!