QGraphicsView and item focus

[Micawber]

Hello,

This is my first post so please be gentle.

I am having trouble getting keyPressEvents in a QGraphicsItem to work. What I have is a QDialog that builds (in the QDialog constructor) a QGraphicsView, creates a QGraphicsScene, initializes two QGraphicsItems (one is a pixmap the other is a sort of "cursor" that is displayed on top of the pixmap at various locations) then places the items in the scene and then sets the scene in the view. I then set the focus to the "cursor" object by setting setFlags( IsFocusable ) and calling Item.setFocus().

I have overridden the QKeyEvent method in my cursor and am looking for the 'N' key, but it doesn't show up.

I appreciate any help you may give as I don't have much hair left...

Here is some c++ code (I'm still learning c++ and probably will be for quite some time)...

// imap_cal_cursor.h
#include <QGraphicsItem>
#include <QObject>
 
class CImapCalCursor : public QObject, public QGraphicsItem
{
    Q_OBJECT
 
public:
    CImapCalCursor();
    void keyPressEvent( QKeyEvent *event );
}
 
 
//imap_cal_cursor.cpp
#include "imap_cal_cursor.h"
 
#include <QGraphicsScene>
#include <QPainter>
#include <QStyleOption>
#include <QKeyEvent>
 
#include "syslog.h"
 
CImapCalCursor::CImapCalCursor() : QObject(), QGraphicsItem()
{
}
 
void CImapCalCursor::keyPressEvent( QKeyEvent *event )
{
    switch (event->key()) {
        case Qt::Key_N:
            syslog( LOG_DEBUG, "DEBUG: Received Key_N event" );
            break;
    }
}
 
 
// calibration_dialog.h
#include <QDialog>
#include <QDialogButtonBox>
#include "imap_cal_image.h"
#include "imap_cal_cursor.h"
 
class CCalibration : public QDialog
{
    Q_OBJECT
 
public:
    QDialogButtonBox *buttonBox;
    QGraphicsView *graphix_area;
 
protected:
    class CImapCalImage Image;
    class CImapCalCursor cur;
    QGraphicsScene *Scene;
    QList< QPoint > list;
    int   current_list_index;
    QGraphicsPixmapItem *pixmapItem;
 
public:
  CCalibration( QWidget * parent = 0, PEZG_COMMBLK EZGSharedMemPtr = NULL );
};
 
 
//calibration_dialog.cpp
#include <QtGui>
#include <QColor>
 
#include "calibration_dialog.h"
#include "syslog.h"
 
CCalibration::CCalibration(QWidget * parent, PEZG_COMMBLK EZGSharedMemPtr )
    : QDialog(parent)
{
    PIM_DIGBUFFER SourceImagePtr;
    imageHeader   *SourceImageHeaderPtr;
    unsigned char *SourceImageDataPtr;
 
    SourceImagePtr = &EZGSharedMemPtr->sImProcDigBuffer;
    SourceImageHeaderPtr = &SourceImagePtr->Header;
    SourceImageDataPtr = SourceImagePtr->image;
 
    setObjectName(QString::fromUtf8("Calibration_Dialog"));
    buttonBox = new QDialogButtonBox( this );
    buttonBox->setObjectName(QString::fromUtf8("buttonBox"));
    buttonBox->setGeometry(QRect(400, 630, 161, 32));
    buttonBox->setOrientation(Qt::Horizontal);
    buttonBox->setStandardButtons(QDialogButtonBox::Cancel|QDialogButtonBox::NoButton|QDialogButtonBox::Ok);
 
    graphix_area = new QGraphicsView( this );
    graphix_area->setObjectName(QString::fromUtf8("graphix_area"));
    graphix_area->setGeometry(QRect(20, 40, 951, 571));
    graphix_area->setCacheMode(QGraphicsView::CacheBackground);
    graphix_area->setRenderHint(QPainter::Antialiasing);
 
    Scene = new QGraphicsScene( this );
 
    Image = CImapCalImage( SourceImageDataPtr, SourceImageHeaderPtr->imWidth, SourceImageHeaderPtr->imHeight, QImage::Format_Indexed8 );
    Image.GenerateColorMap();
    pixmapItem = Scene->addPixmap( QPixmap::fromImage( Image ) );
 
    list = Image.ScanForPoints();
    if( list.isEmpty() || list.size() == 0 ) {
        syslog( LOG_ERR, "ERROR: ScanForPoints returned empty list" );
        current_list_index = -1;
    }
    else {
        current_list_index = 0;
        Scene->addItem( &cur );
        cur.setZValue( 10 );
        cur.setPos( pixmapItem->mapToParent( list[ current_list_index ] ) );
        cur.setFlag( QGraphicsItem::ItemIsFocusable );
    }
 
    graphix_area->setScene( Scene );
    Scene->setFocusItem( &cur );
 
    QSize size(988, 684);
    size = size.expandedTo(minimumSizeHint());
    resize(size);
}

// imap_cal_cursor.h
#include <QGraphicsItem>
#include <QObject>

class CImapCalCursor : public QObject, public QGraphicsItem
{
    Q_OBJECT

public:
    CImapCalCursor();
    void keyPressEvent( QKeyEvent *event );
}


//imap_cal_cursor.cpp
#include "imap_cal_cursor.h"

#include <QGraphicsScene>
#include <QPainter>
#include <QStyleOption>
#include <QKeyEvent>

#include "syslog.h"

CImapCalCursor::CImapCalCursor() : QObject(), QGraphicsItem()
{
}

void CImapCalCursor::keyPressEvent( QKeyEvent *event )
{
    switch (event->key()) {
        case Qt::Key_N:
            syslog( LOG_DEBUG, "DEBUG: Received Key_N event" );
            break;
    }
}


// calibration_dialog.h
#include <QDialog>
#include <QDialogButtonBox>
#include "imap_cal_image.h"
#include "imap_cal_cursor.h"

class CCalibration : public QDialog
{
    Q_OBJECT

public:
    QDialogButtonBox *buttonBox;
    QGraphicsView *graphix_area;

protected:
    class CImapCalImage Image;
    class CImapCalCursor cur;
    QGraphicsScene *Scene;
    QList< QPoint > list;
    int   current_list_index;
    QGraphicsPixmapItem *pixmapItem;

public:
  CCalibration( QWidget * parent = 0, PEZG_COMMBLK EZGSharedMemPtr = NULL );
};


//calibration_dialog.cpp
#include <QtGui>
#include <QColor>

#include "calibration_dialog.h"
#include "syslog.h"

CCalibration::CCalibration(QWidget * parent, PEZG_COMMBLK EZGSharedMemPtr )
    : QDialog(parent)
{
    PIM_DIGBUFFER SourceImagePtr;
    imageHeader   *SourceImageHeaderPtr;
    unsigned char *SourceImageDataPtr;

    SourceImagePtr = &EZGSharedMemPtr->sImProcDigBuffer;
    SourceImageHeaderPtr = &SourceImagePtr->Header;
    SourceImageDataPtr = SourceImagePtr->image;

    setObjectName(QString::fromUtf8("Calibration_Dialog"));
    buttonBox = new QDialogButtonBox( this );
    buttonBox->setObjectName(QString::fromUtf8("buttonBox"));
    buttonBox->setGeometry(QRect(400, 630, 161, 32));
    buttonBox->setOrientation(Qt::Horizontal);
    buttonBox->setStandardButtons(QDialogButtonBox::Cancel|QDialogButtonBox::NoButton|QDialogButtonBox::Ok);

    graphix_area = new QGraphicsView( this );
    graphix_area->setObjectName(QString::fromUtf8("graphix_area"));
    graphix_area->setGeometry(QRect(20, 40, 951, 571));
    graphix_area->setCacheMode(QGraphicsView::CacheBackground);
    graphix_area->setRenderHint(QPainter::Antialiasing);

    Scene = new QGraphicsScene( this );

    Image = CImapCalImage( SourceImageDataPtr, SourceImageHeaderPtr->imWidth, SourceImageHeaderPtr->imHeight, QImage::Format_Indexed8 );
    Image.GenerateColorMap();
    pixmapItem = Scene->addPixmap( QPixmap::fromImage( Image ) );

    list = Image.ScanForPoints();
    if( list.isEmpty() || list.size() == 0 ) {
        syslog( LOG_ERR, "ERROR: ScanForPoints returned empty list" );
        current_list_index = -1;
    }
    else {
        current_list_index = 0;
        Scene->addItem( &cur );
        cur.setZValue( 10 );
        cur.setPos( pixmapItem->mapToParent( list[ current_list_index ] ) );
        cur.setFlag( QGraphicsItem::ItemIsFocusable );
    }

    graphix_area->setScene( Scene );
    Scene->setFocusItem( &cur );

    QSize size(988, 684);
    size = size.expandedTo(minimumSizeHint());
    resize(size);
}

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[Gopala Krishna]

Hello,

This is my first post so please be gentle.

Welcome to the qtcentre!

I am having trouble getting keyPressEvents in a QGraphicsItem to work. What I have is a QDialog that builds (in the QDialog constructor) a QGraphicsView, creates a QGraphicsScene, initializes two QGraphicsItems (one is a pixmap the other is a sort of "cursor" that is displayed on top of the pixmap at various locations) then places the items in the scene and then sets the scene in the view. I then set the focus to the "cursor" object by setting setFlags( IsFocusable ) and calling Item.setFocus().

I have overridden the QKeyEvent method in my cursor and am looking for the 'N' key, but it doesn't show up.

Well i think , the cursor item is sensing key events properly but syslog's output should be invisible for some reason. I wrote a small example and this works fine in windows. I just used message box to make sure i get feedback when a key is pressed. Here is code

#include <QtGui>
 
class KeyReceiver : public QGraphicsEllipseItem
{
public:
	KeyReceiver(const QRectF& rect) : QGraphicsEllipseItem(rect)
	{
		setFlags(ItemIsMovable | ItemIsFocusable | QGraphicsItem::ItemIsSelectable);
	}
 
	void keyPressEvent ( QKeyEvent * event )
	{
		if(event->key() == Qt::Key_N)
			QMessageBox::warning(0,"dg","HF");
		QGraphicsEllipseItem::keyPressEvent(event);
	}
};
 
int main(int argc,char *argv[])
{
	QApplication app(argc,argv);
	QGraphicsScene scene(0,0,1000,800);
	KeyReceiver *r = new KeyReceiver(QRectF(10,10,100,80));
	scene.addItem(r);
	QGraphicsView view(&scene);
	view.show();
	r->setFocus();
	return app.exec();
}

#include <QtGui>

class KeyReceiver : public QGraphicsEllipseItem
{
public:
	KeyReceiver(const QRectF& rect) : QGraphicsEllipseItem(rect)
	{
		setFlags(ItemIsMovable | ItemIsFocusable | QGraphicsItem::ItemIsSelectable);
	}

	void keyPressEvent ( QKeyEvent * event )
	{
		if(event->key() == Qt::Key_N)
			QMessageBox::warning(0,"dg","HF");
		QGraphicsEllipseItem::keyPressEvent(event);
	}
};

int main(int argc,char *argv[])
{
	QApplication app(argc,argv);
	QGraphicsScene scene(0,0,1000,800);
	KeyReceiver *r = new KeyReceiver(QRectF(10,10,100,80));
	scene.addItem(r);
	QGraphicsView view(&scene);
	view.show();
	r->setFocus();
	return app.exec();
}

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[Micawber]

I tried calling QMessageBox in the keyPressEvent method but still no dice.

I thought that perhaps since the dialog was still under construction and the items not yet visible, the calls to setFocus were being ignored. So I added a SetFocus method to my extended QDialog class and called it from my main application after I called show(). Still no dice.

Obviously I am not understanding some key concept either in Qt or in C++.

[Micawber]

OK some more information...

If I change my cursor class such that it is only a descendant of QGraphicsItem (remove the QObject ancestry and the timer stuff) it works. Any clue as to why having QObject ancestry would cause it to break???

I need the timers and to emit signals.