Mouse press event in a QGraphicsScene

[Lykurg]

Hi,
an old problem is bothering me and I can't get it fixed. After double clicking a custom QGraphicsTextItem, I want to move the cursor of the QTextDocument to the position under the cursor. This is the behavior you can achieve if you press three times the mouse button. So I thought just send a mouse event, but I fail. Here my files:

#include <QtGui>
#include "myitem.h"
 
int main(int argc, char *argv[])
{
    QApplication a(argc, argv);
 
    MyItem *it = new MyItem();
    it->setPlainText("String to edit");
 
    QGraphicsScene scene;
    scene.addItem(it);
 
    QGraphicsView view(&scene);
    view.show();
 
    return a.exec();
}

#include <QtGui>
#include "myitem.h"

int main(int argc, char *argv[])
{
    QApplication a(argc, argv);
    
    MyItem *it = new MyItem();
    it->setPlainText("String to edit");
    
    QGraphicsScene scene;
    scene.addItem(it);
    
    QGraphicsView view(&scene);
    view.show();
    
    return a.exec();
}

To copy to clipboard, switch view to plain text mode 

#ifndef MYITEM_H
#define MYITEM_H
 
#include <QtGui>
 
class MyItem : public QGraphicsTextItem
{
    Q_OBJECT
 
public:
    MyItem(QGraphicsItem *parent = 0);
    QMouseEvent *e;
 
protected:
    void mouseDoubleClickEvent(QGraphicsSceneMouseEvent *event);
    void focusOutEvent(QFocusEvent *event);
};
 
#endif /* MYITEM_H */

#ifndef MYITEM_H
#define MYITEM_H

#include <QtGui>

class MyItem : public QGraphicsTextItem
{
    Q_OBJECT

public:
    MyItem(QGraphicsItem *parent = 0);
    QMouseEvent *e;

protected:
    void mouseDoubleClickEvent(QGraphicsSceneMouseEvent *event);
    void focusOutEvent(QFocusEvent *event);
};

#endif /* MYITEM_H */

To copy to clipboard, switch view to plain text mode 

#include "myitem.h"
 
MyItem::MyItem(QGraphicsItem *parent)
    : QGraphicsTextItem(parent)
{
    setTextInteractionFlags(Qt::LinksAccessibleByMouse);
}
 
void MyItem::mouseDoubleClickEvent(QGraphicsSceneMouseEvent *event)
{
    if (textInteractionFlags() & Qt::TextEditorInteraction)
    {
        QGraphicsTextItem::mouseDoubleClickEvent(event);
    }
    else
    {
        setTextInteractionFlags(Qt::TextEditorInteraction);
        // HERE SOME MAGIC CODE TO MOVE THE CURSOR
        // which is by default at 0 after calling setTextInteractionFlags(Qt::TextEditorInteraction).
    }
}
 
void MyItem::focusOutEvent(QFocusEvent *event)
{
    setTextInteractionFlags(Qt::LinksAccessibleByMouse);
    QGraphicsTextItem::focusOutEvent(event);
}

#include "myitem.h"

MyItem::MyItem(QGraphicsItem *parent)
    : QGraphicsTextItem(parent)
{
    setTextInteractionFlags(Qt::LinksAccessibleByMouse);
}

void MyItem::mouseDoubleClickEvent(QGraphicsSceneMouseEvent *event)
{
    if (textInteractionFlags() & Qt::TextEditorInteraction)
    {
        QGraphicsTextItem::mouseDoubleClickEvent(event);
    }
    else
    {
        setTextInteractionFlags(Qt::TextEditorInteraction);
        // HERE SOME MAGIC CODE TO MOVE THE CURSOR
        // which is by default at 0 after calling setTextInteractionFlags(Qt::TextEditorInteraction).
    }
}

void MyItem::focusOutEvent(QFocusEvent *event)
{
    setTextInteractionFlags(Qt::LinksAccessibleByMouse);
    QGraphicsTextItem::focusOutEvent(event);
}

To copy to clipboard, switch view to plain text mode 

I need to set the editor functionability only after a double click. All attempts to redirect the event leads in a total selection of the text. And creating different QMouseEvents and send them via QCoreApplication::sendEvent ended somewhere in Nirvana...

Any hints are welcome. Even code, as you know I am to lazy to do the work by my own, and it's your job to do my work...

Thanks,

Lykurg

[shentian]

Hi,
my idea was to directly call QGraphicsItem::mousePressEvent. For this, you need to create a QGraphicsSceneMouseEvent. According to the Qt API Docs, there seems to be no way, but after a peek into the source code of QGraphicsScene, I came up with the following:

void MyItem::mouseDoubleClickEvent(QGraphicsSceneMouseEvent *event)
{
    if (textInteractionFlags() & Qt::TextEditorInteraction)
    {
        QGraphicsTextItem::mouseDoubleClickEvent(event);
    }
    else
    {
        setTextInteractionFlags(Qt::TextEditorInteraction);
        // HERE SOME MAGIC CODE TO MOVE THE CURSOR
        QGraphicsSceneMouseEvent newEvent(QEvent::GraphicsSceneMousePress);
        newEvent.setScenePos(event->scenePos());
        newEvent.setPos(event->pos());
        newEvent.setButtons(event->buttons());
        newEvent.setButton(event->button());
        newEvent.setModifiers(event->modifiers());
        QGraphicsTextItem::mousePressEvent(&newEvent);
    }
}

void MyItem::mouseDoubleClickEvent(QGraphicsSceneMouseEvent *event)
{
    if (textInteractionFlags() & Qt::TextEditorInteraction)
    {
        QGraphicsTextItem::mouseDoubleClickEvent(event);
    }
    else
    {
        setTextInteractionFlags(Qt::TextEditorInteraction);
        // HERE SOME MAGIC CODE TO MOVE THE CURSOR
        QGraphicsSceneMouseEvent newEvent(QEvent::GraphicsSceneMousePress);
        newEvent.setScenePos(event->scenePos());
        newEvent.setPos(event->pos());
        newEvent.setButtons(event->buttons());
        newEvent.setButton(event->button());
        newEvent.setModifiers(event->modifiers());
        QGraphicsTextItem::mousePressEvent(&newEvent);
    }
}

To copy to clipboard, switch view to plain text mode 

It's a bit nasty, since it uses non-API public members of QGraphicsSceneMouseEvent (marked as 'internal'), but it works...

[Lykurg]

It's a bit nasty, since it uses non-API public members of QGraphicsSceneMouseEvent (marked as 'internal'),

I intended to avoid use internal stuff...

but it works...

...yeah, what the heck, what works works, I will use that. By the way I also guess that they wont change so much on that.
Thanks very much, that you have spend your time looking through the sources, to get a solution for my problem, I appreciate that!

But I am still confused why something link that don't work:

QMouseEvent ne(QEvent::MouseButtonPress, event->pos().toPoint(), event->button(), event->buttons(), event->modifiers());
QApplication::sendEvent(this, &ne);

QMouseEvent ne(QEvent::MouseButtonPress, event->pos().toPoint(), event->button(), event->buttons(), event->modifiers());
QApplication::sendEvent(this, &ne);

To copy to clipboard, switch view to plain text mode 

The event is delivered to MyItem, says my eventFilter, but the reimp MyItem::mousePressEvent() isn't invoked. Also used QCursor:: pos(), Qt::LeftButton...


Lykurg

[shentian]

MyItem::mousePressEvent() isn't invoked because you are sending a QMouseEvent, not a QGraphicsSceneMouseEvent. And sadly, API doesn't allow to create a QGraphicsSceneMouseEvent

Maybe you can try to send a QMouseEvent to the QGraphicsView, which will translate it to a QGraphicsSceneMouseEvent.

I tried this, but it doesn't seem to work either:

QGraphicsView* view = scene()->views().first();
QMouseEvent ne(QEvent::MouseButtonPress, view->mapFromGlobal(event->screenPos()), event->button(), event->buttons(), event->modifiers());
QApplication::sendEvent(view, ne);

QGraphicsView* view = scene()->views().first();
QMouseEvent ne(QEvent::MouseButtonPress, view->mapFromGlobal(event->screenPos()), event->button(), event->buttons(), event->modifiers());
QApplication::sendEvent(view, ne);

To copy to clipboard, switch view to plain text mode