Encountering segmentation fault while accessing QLineEdit

[qtzcute]

Hi,

I am encountering a Segmentation fault while trying to write somethiing in a LineEdit widget (defined in Ui_MainWindow) from another class sqMap which inherits QGraphicsItem and Ui_MainWindow. The output of gdb's backtracking is as under:

Program received signal SIGSEGV, Segmentation fault.
[Switching to Thread 0xb6e8e8e0 (LWP 4644)]
QLineEditPrivate::setText (this=0x0, txt=@0xbff2c200, pos=-1, edited=false) at widgets/qlineedit.cpp:2909
2909        q->resetInputContext();
(gdb) bt
#0  QLineEditPrivate::setText (this=0x0, txt=@0xbff2c200, pos=-1, edited=false) at widgets/qlineedit.cpp:2909
#1  0xb7b9018b in QLineEdit::setText (this=0x80ce468, text=@0xbff2c200) at widgets/qlineedit.cpp:388
#2  0x08057e3f in sqMap::paint (this=0x80f6278, painter=0xbff2d3ac, option=0x81b7d78, widget=0x8123170) at sqMap.cpp:95
#3  0xb7d8122d in _q_paintItem (item=0x80f6280, painter=0xbff2d3ac, option=0x81b7d78, widget=0x8123170, useWindowOpacity=true,
    painterStateProtection=true) at graphicsview/qgraphicsscene.cpp:3754
#4  0xb7d83eca in QGraphicsScenePrivate::drawItemHelper (item=0x80f6280, painter=0xbff2d3ac, option=0x81b7d78, widget=0x8123170,
    painterStateProtection=<value optimized out>) at graphicsview/qgraphicsscene.cpp:3810
#5  0xb7d85049 in QGraphicsScene::drawItems (this=0x81a6fb0, painter=0xbff2d3ac, numItems=2, items=0x8140440, options=0x81b7cf4,
    widget=0x8123170) at graphicsview/qgraphicsscene.cpp:4036
#6  0xb7d98aac in QGraphicsView::drawItems (this=0x80dcf28, painter=0xbff2d3ac, numItems=2, items=0x8140440, options=0x81b7cf4)
---Type <return> to continue, or q <return> to quit---bt
    at graphicsview/qgraphicsview.cpp:3351
#7  0xb7da20c4 in QGraphicsView::paintEvent (this=0x80dcf28, event=0xbff2d8fc) at graphicsview/qgraphicsview.cpp:3096
#8  0xb784384b in QWidget::event (this=0x80dcf28, event=0xbff2d8fc) at kernel/qwidget.cpp:7301
#9  0xb7b7aec3 in QFrame::event (this=0x80dcf28, e=0xbff2d8fc) at widgets/qframe.cpp:651
#10 0xb7c119ef in QAbstractScrollArea::viewportEvent (this=0x80dcf28, e=0x80f9f68) at widgets/qabstractscrollarea.cpp:943
#11 0xb7d9f70f in QGraphicsView::viewportEvent (this=0x80dcf28, event=0xbff2d8fc) at graphicsview/qgraphicsview.cpp:2337
#12 0xb7c13f95 in QAbstractScrollAreaFilter::eventFilter (this=0x80d9710, o=0x8123170, e=0xbff2d8fc)
    at widgets/qabstractscrollarea_p.h:96
#13 0xb739cc4a in QCoreApplicationPrivate::sendThroughObjectEventFilters (this=0x805f1d8, receiver=0x8123170, event=0xbff2d8fc)
    at kernel/qcoreapplication.cpp:694

Program received signal SIGSEGV, Segmentation fault.
[Switching to Thread 0xb6e8e8e0 (LWP 4644)]
QLineEditPrivate::setText (this=0x0, txt=@0xbff2c200, pos=-1, edited=false) at widgets/qlineedit.cpp:2909
2909        q->resetInputContext();
(gdb) bt
#0  QLineEditPrivate::setText (this=0x0, txt=@0xbff2c200, pos=-1, edited=false) at widgets/qlineedit.cpp:2909
#1  0xb7b9018b in QLineEdit::setText (this=0x80ce468, text=@0xbff2c200) at widgets/qlineedit.cpp:388
#2  0x08057e3f in sqMap::paint (this=0x80f6278, painter=0xbff2d3ac, option=0x81b7d78, widget=0x8123170) at sqMap.cpp:95
#3  0xb7d8122d in _q_paintItem (item=0x80f6280, painter=0xbff2d3ac, option=0x81b7d78, widget=0x8123170, useWindowOpacity=true,
    painterStateProtection=true) at graphicsview/qgraphicsscene.cpp:3754
#4  0xb7d83eca in QGraphicsScenePrivate::drawItemHelper (item=0x80f6280, painter=0xbff2d3ac, option=0x81b7d78, widget=0x8123170,
    painterStateProtection=<value optimized out>) at graphicsview/qgraphicsscene.cpp:3810
#5  0xb7d85049 in QGraphicsScene::drawItems (this=0x81a6fb0, painter=0xbff2d3ac, numItems=2, items=0x8140440, options=0x81b7cf4,
    widget=0x8123170) at graphicsview/qgraphicsscene.cpp:4036
#6  0xb7d98aac in QGraphicsView::drawItems (this=0x80dcf28, painter=0xbff2d3ac, numItems=2, items=0x8140440, options=0x81b7cf4)
---Type <return> to continue, or q <return> to quit---bt
    at graphicsview/qgraphicsview.cpp:3351
#7  0xb7da20c4 in QGraphicsView::paintEvent (this=0x80dcf28, event=0xbff2d8fc) at graphicsview/qgraphicsview.cpp:3096
#8  0xb784384b in QWidget::event (this=0x80dcf28, event=0xbff2d8fc) at kernel/qwidget.cpp:7301
#9  0xb7b7aec3 in QFrame::event (this=0x80dcf28, e=0xbff2d8fc) at widgets/qframe.cpp:651
#10 0xb7c119ef in QAbstractScrollArea::viewportEvent (this=0x80dcf28, e=0x80f9f68) at widgets/qabstractscrollarea.cpp:943
#11 0xb7d9f70f in QGraphicsView::viewportEvent (this=0x80dcf28, event=0xbff2d8fc) at graphicsview/qgraphicsview.cpp:2337
#12 0xb7c13f95 in QAbstractScrollAreaFilter::eventFilter (this=0x80d9710, o=0x8123170, e=0xbff2d8fc)
    at widgets/qabstractscrollarea_p.h:96
#13 0xb739cc4a in QCoreApplicationPrivate::sendThroughObjectEventFilters (this=0x805f1d8, receiver=0x8123170, event=0xbff2d8fc)
    at kernel/qcoreapplication.cpp:694

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Here are some details of the classes used:

Ui_MainWindow.h
Generated with the help of Qt Designer but it was defined and used as a simple class instead of a namespace.

sqMap.h
My defined class used for displaying a map of squares.

class sqMap : public QObject, public QGraphicsItem, public Ui_MainWindow
 {
     Q_OBJECT
 
 public:
     sqMap(double Width, double Height, ps_info* processInformation, QGraphicsItem *parent = 0);
     QRectF boundingRect() const;
     void paint(QPainter *painter, const QStyleOptionGraphicsItem *option, QWidget *widget = 0);
     void updateLocation(int size);
     double getWidth(); 
     double getHeight();
 
protected:
    void hoverEnterEvent(QGraphicsSceneHoverEvent *e);
    void hoverLeaveEvent(QGraphicsSceneHoverEvent *e);
    void mousePressEvent(QGraphicsSceneMouseEvent *e);
    void mouseReleaseEvent(QGraphicsSceneMouseEvent *e); 
 private:
	QColor color;
	int width;
	int height;
	bool m_isHovered;
	bool m_mouseIsDown; //caters for whether an item has been clicked
 
 };

class sqMap : public QObject, public QGraphicsItem, public Ui_MainWindow
 {
     Q_OBJECT

 public:
     sqMap(double Width, double Height, ps_info* processInformation, QGraphicsItem *parent = 0);
     QRectF boundingRect() const;
     void paint(QPainter *painter, const QStyleOptionGraphicsItem *option, QWidget *widget = 0);
     void updateLocation(int size);
     double getWidth(); 
     double getHeight();

protected:
    void hoverEnterEvent(QGraphicsSceneHoverEvent *e);
    void hoverLeaveEvent(QGraphicsSceneHoverEvent *e);
    void mousePressEvent(QGraphicsSceneMouseEvent *e);
    void mouseReleaseEvent(QGraphicsSceneMouseEvent *e); 
 private:
	QColor color;
	int width;
	int height;
	bool m_isHovered;
	bool m_mouseIsDown; //caters for whether an item has been clicked

 };

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Definition of paint function for sqMap

void sqMap::paint(QPainter *painter, const QStyleOptionGraphicsItem *option, QWidget *widget)
 {
     QPen pen;
    bool isSelected = (option->state & QStyle::State_Selected) == QStyle::State_Selected;
     painter->setBrush(m_isHovered ? Qt::red : color);
     painter->drawRect(0,-265,width,height);
     if (m_mouseIsDown)
	{
		lineEdit->setText("something");
	}
 }

void sqMap::paint(QPainter *painter, const QStyleOptionGraphicsItem *option, QWidget *widget)
 {
     QPen pen;
    bool isSelected = (option->state & QStyle::State_Selected) == QStyle::State_Selected;
     painter->setBrush(m_isHovered ? Qt::red : color);
     painter->drawRect(0,-265,width,height);
     if (m_mouseIsDown)
	{
		lineEdit->setText("something");
	}
 }

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My Objective:
When a square is clicked 'something' may display in the LineEdit

Problem:
Squares show up finely but a click on it causes Segmetation fault.

I am struggling for a while to figure out whats wrong and your help may save me a lot of time.

Thanks