Application crashes when mouse moves



  • Hello guys,

    i am writing an application that trains letter typing. Upon writing a wrong letter, it's color is changed into red and for a correct letter its color is made green .. There is a timer in the window to calculate the typing speed.

    The application crashes when i move the mouse over the text area and tries to close the window .. I disconnect the timer before i close the window ..

    -> Unfortunately i don't how to use valgrind .. I installed it but it seems not correctly working ..
    -> is there a way to trun garbage collection to ON?

    Any idea how can i debug this point .. Before it crashes, it shows these lines?

    0 QtGui 0x0000000100995ce0 QApplication::desktop() + 32
    1 QtGui 0x0000000100946f6b flipPoint(CGPoint const&) + 27
    2 QtGui 0x0000000100949ded qt_mac_getTargetForMouseEvent(NSEvent*, QEvent::Type, QPoint&, QPoint&, QWidget*, QWidget**) + 205
    3 QtGui 0x000000010094a77a qt_mac_handleMouseEvent(NSEvent*, QEvent::Type, Qt::MouseButton,

    any help is appreciated ..


  • Lifetime Qt Champion

    Hi,

    Can you run your application through the debugger ? That should already give you some information about what happens.

    Also, what version of Qt/OS X are you using ?



  • When i run through the debugger it says the inferior stopped because
    it received a signal from the os
    EXC_bad_access
    could not access memory

    Mac os: 10.7.5
    QT creator : 2.4.1
    based on 4.7.6
    build on jan 25 12


  • Lifetime Qt Champion

    You should have a backtrace of what is happening when the crash occurred, what is it ?



  • the object window -> creates another highlighting object
    at some instance which i don't know when (may be when writing in high speed), the highlighting object is called, it tries to make the paint event but at the same time, there might be other events (i don't know what is it) and they crash together ..

    It seems that some object is not correctly deleted ... i don't know how to find it ..



  • I installed valgrind in /usr/bin/ i see in it a file called vgrind
    but when i do in QT - Analyze - Valgrind analyze memory or function i get

    Analyzing memory of /login
    ** Error: "valgrind" could not be started: No such file or directory **
    ** Analyzing finished **

    I installed valgrind this way

    cd /Volumes/Macintosh\ HD/Users/so/Downloads/valgrind-3.9.0
    ./configure --prefix=/usr/bin
    make
    sudo make install


  • Lifetime Qt Champion

    Try giving the full path in Qt Creator.

    Are you using delete on these objects or call deleteLater ?



  • yes i use delete after the object finishes ..
    I managed to install valgrind correctly and now i have the analyze-memory and function working .. which one should i use to find what hangs up while deleting the object?


  • Lifetime Qt Champion

    If these are QObject derived classes you should rather use deleteLater



  • Lets try to find the mistake because i am struggling since 2 days and don't see it ..

    Header file
    @
    #ifndef PRACTISING_H
    #define PRACTISING_H

    #include <QKeyEvent>
    #include <QWidget>

    #include "highlighter.h"
    #include "typingtutormain.h" //1
    #include "keygramform.h"

    #include <QBitArray>
    #include "keyboardmap.h"
    #include "practisehandwin.h"
    //#include "qgarbagecollector.h"

    namespace Ui {
    class practising;

    }

    class practising : public QDialog
    {
    Q_OBJECT

    public:
    practising(bool traintestmode, int mintext, int maxtext, QWidget *parent);
    ~practising();
    TypingTutorMain *mainparentform; //2
    void handwindowcloseevent();
    inline void setWindowPositionAndSize(const QRect& fg) {resize(fg.size()); move(fg.topLeft());}
    inline QRect windowPositionAndSize() const { return QRect(pos(), size()); }

    private slots:
    void on_previous_Btn_clicked();
    void on_next_Btn_clicked();
    void on_start_Btn__clicked();
    void on_stop_Btn_clicked();
    void timercount(void);
    void lostfocus();

    private:
    Ui::practising *ui;
    QPointer <Highlighter> highlighter;
    QPointer <KeyBoardMap> kbmap;
    QPointer <QDesktopWidget> d; // for window size
    QTime PracticeTimer; // Timer in the practise (Stop watch)
    QPointer <QTimer> PractiseTimerFire; // Timer fireing each 1 sec to count the stop watch
    // QScopedPointer <QTimer> PractiseTimerFire;
    QPointer <practisehandwin> handpop;
    QPointer <QScrollBar> sb;

    };

    #endif // PRACTISING_H

    @

    Highlighter class
    @
    class Highlighter : public QSyntaxHighlighter
    {
    Q_OBJECT
    public:
    @

    keyboard map class
    @

    class KeyBoardMap : public QDialog
    {
    Q_OBJECT

    public:

    @

    @
    practising::~practising()
    {

    qDebug() << "practise done return";
    done(1);
    qDebug() << "practising::~practising";
    
    //delete ui; // it will be deleted there in the calling form
    

    }

    void practising::closeEvent(QCloseEvent *event)
    {
    qDebug()<< "practising::closeEvent";

    PractiseTimerFire->stop();
    QObject::disconnect(PractiseTimerFire,0);
    
    qDebug()<<"to delete highlighter";
    delete highlighter;
    
    qDebug() << "to delete keyboard map ";
    delete kbmap;
    
    qDebug() << "to delete timer";
    delete PractiseTimerFire;
    
    qDebug() << "to delete handpop";
    delete handpop;
    
    qDebug() << " delete scroll bar";
    delete sb;
    
    qDebug() << " ------------";
    
    
    if (handwindowenabled==true) //if handwindow is open
    {
       qDebug() << "practising:close-1";
       //handpop.data()->close();
       //QMetaObject::invokeMethod(handpop, "close", Qt::QueuedConnection);//important line
       //delete handpop;
       //handpop.data()->deleteLater();
    }
    this->mainparentform->show();
    //event->accept();
    
    qDebug() << "closesevent - first part pass" << handpop.isNull();
    
    
    
    delete d;
    //delete inst_speed;
    //delete inst_speed_correct;
    //delete inst_speed_correct_diff;
    //delete inst_speed_timepassd;
    
    //Practise_AddToDataBase(); // Add data to dB
    
    qDebug() << "closever 2";
    //Q_UNUSED(event); //unreferenced formal parameter
    qDebug() << "closever 3";
    quitpractise = true;
    
    //delete ui;
    

    }

    @



  • should QSyntaxHighlighter be also treated with deletelater?


  • Lifetime Qt Champion

    You are doing things in a pretty unusual way.

    Why use closeEvent to destroy everything ? In your case the destructor is there for that.

    Why are you using QPointer for everything ? It's not it's purpose

    Also, you are probably deleting objects that have parent that would be destroyed automatically when "practicing" is destroyed.

    Also, why windowPositionAndSize ? look at QWidget::geometry()



  • I am still learning QT ... I will take the pointer one by one for me to learn ..
    First, lets take the QTimer, i want to get initialized when i press on start button
    @
    QTimer *PractiseTimerFire = new QTimer(this);
    connect(PractiseTimerFire, SIGNAL(timeout()),this, SLOT(timercount()));
    PractiseTimerFire->start(1000);
    @

    I need to disable it when i click on the Stop button, but it is then not defined .. I need to cast it but don't know how .. Could you please help me?



  • I use the widget::close event because the widget is a second window called from a first window , and i want the first window to be visible back, so i made a parent child mechanism ..



  • I have it now solved ... I sent a message from the child to a parent method called (closepractise) in order to close the child .. it worked ..

    Vielen Dank .. Allerdings ich brauche Unterst├╝tzung in der Zukunft


  • Lifetime Qt Champion

    Depending on how you create the dialog you should not even need that



  • I want to ask a simple question because i don't know its answer, Please ..

    lets says in mainwindow, i create a new window called A
    QWidget A=new QWidget(0)

    Inside A, i want to create a new window that is located beside A and it should be a child ..
    If i say
    QWidget B=new QWidget (A) -> it will be inside window A
    so i must call it
    QWidget B=new QWidget (0) -> to make a new window
    but then B is not a child of A and will not close if A is closed ..


  • Lifetime Qt Champion

    Then it all depends on how you use that window. Is B a member of A ? If so you can e.g. reimplement closeEvent and also close B in there. If not create a signal that you emit from A when it's closing and connect it to B's close slot



  • What you mean by B member of A? B is a window, A is also a window
    I imlemented your signalling idea but i want ask : I used to do it the following way, is it correct?

    @
    qPointer <handpop> qWidget;
    QWidget handpop = new QWidget (0);

    if (!handpop.isNull())
    {
        handpop.data()->close();
    }
    delete handpop;
    

    @



  • I tested the signal method but it is not good, it breaks
    in practising i create a handwindow
    @
    handpop = new practisehandwin(0);
    connect(this,SIGNAL(destroyed()),handpop.data(),SLOT(close()));
    @

    I tested also with by emitting a signal to the handpop to close it self ..



  • In the main module called typingmain, i do the following with the practiseform

    typingmain.cpp
    @
    QPointer <practising> practiseform = new practising(true,1,0,0); // practise mode, default lesson min=1, lessonmax=0, new parent window=0
    practiseform->mainparentform=this; connect(practiseform.data(),SIGNAL(ToTypingDeletePractise(int)),this,SLOT(CloseChild(int));
    this->hide();
    int x=practiseform->exec();
    if (qDebugDemo>=2) {qDebug() << "returned back";}
    this->show();
    if (qDebugDemo>=1) {qDebug () << "practise finished with return =" << x << " is window reset?" << practiseform.isNull();}
    if (! practiseform.isNull())
    {
    qDebug() << "delete practiseform";
    //delete practiseform;
    }
    @

    In practising, i load the handpop when a button is clicked
    practising.cpp
    @
    if (!handwindowenabled)
    {
    handpop = new practisehandwin(0);
    //connect(this,SIGNAL(destroyed()),handpop.data(),SLOT(close()));
    //QScopedPointer<practisehandwin> handpop(new practisehandwin(0));
    }
    @

    Then when it closes, i delete the handpop and emit a signal back to typingmain to delete the practising pointer
    @
    void practising::closeEvent(QCloseEvent *event)
    {
    if (qDebugDemo>=2)
    { qDebug()<< "practising::closeEvent";
    qDebug() << "to delete handpop";
    }
    if (!handpop.isNull())
    {
    //emit(this->ToHandWindowDeleteYourSelf());
    handpop.data()->close();
    }
    delete handpop;

    PractiseTimerFire->stop();
    disconnect(PractiseTimerFire,0);
    
    if (qDebugDemo>=2) {qDebug()<<"to delete highlighter";}
    delete highlighter;
    
    if (qDebugDemo>=2) {qDebug() << "to delete keyboard map ";}
    delete kbmap;
    
    if (qDebugDemo>=2) {qDebug() << "to delete timer";}
    delete PractiseTimerFire;
    
    
    
    if (qDebugDemo>=2) {qDebug() << " delete scroll bar";}
    delete sb;
    
    if (qDebugDemo>=2) {qDebug() << " ------------";}
    
    this->done(1);
    emit(this->ToTypingDeletePractise(1));
    if (qDebugDemo>=2) {qDebug() << "practise close me signal emitted";}
    
    
    
    //this->mainparentform->show();
    //event->accept();
    
    qDebug() << "closesevent - first part pass" << handpop.isNull();
    
    
    //delete inst_speed;
    //delete inst_speed_correct;
    //delete inst_speed_correct_diff;
    //delete inst_speed_timepassd;
    
    //Practise_AddToDataBase(); // Add data to dB
    
    //Q_UNUSED(event); //unreferenced formal parameter
    //qDebug() << "closever 3";
    quitpractise = true;
    //delete ui;
    //event->ignore();
    

    }
    @

    in typingmain
    @
    void TypingTutorMain::CloseChild(int childnumber)
    {
    switch (childnumber)
    {
    case 1:
    if (! practiseform.isNull())
    {
    qDebug()<<"signal received delete practise follows";
    practiseform.data()->deleteLater();
    qDebug() << "is practise deleted?"<< practiseform.isNull();
    }
    }
    }
    @

    Note that if i use
    //QScopedPointer<practising> practiseform(new practising(true,1,0,0));
    it which is the same as QPointer but it deletes it self automatic, it crashes, even if i disable emiting the ToTypingDeletePractise signal

    I don't know if i close the handpop correctly


  • Lifetime Qt Champion

    It looks like your are using dialogs and not just widget and you only use them locally. So just don't create pointers to QDialogs if the logic is:

    Create dialog

    Ask something to the user

    Get result

    Delete dialog

    You really should first go through the examples in Qt's documentation. You are starting to write code that is going to be a nightmare to follow and maintain.


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