QGraphicsTextItem and text cursor position via QPoint

[Lykurg]

Hi,

I have a customized QGraphicsTextItem. By default the item is not editable. If one would like to change the content he has to double click the item:

void MyWordItem::mouseDoubleClickEvent(QGraphicsSceneMouseEvent */*event*/)
{
	setTextInteractionFlags(Qt::TextEditorInteraction);
}

void MyWordItem::mouseDoubleClickEvent(QGraphicsSceneMouseEvent */*event*/)
{
	setTextInteractionFlags(Qt::TextEditorInteraction);
}

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Now every time the blinking cursor is at the position 0, but I want the text cursor to be near the mouse double click position. (Like the result if one click the mouse button a third time.) Looking through QTextCursor, QTextDocument for a function like setTextCursorPos(QPoint) faild (I would like to use event->pos()). Even in the sources I don't figure out how the trolls do it in the mouse press reimp...

Passing the event to QGraphicsTextItem::mouseDoubleClickEvent(event); or QGraphicsTextItem::mousePressEvent(event); ends in a total selection of the content.


Any suggestions?
Thanks

[mhennings]

I know this thread is older than Saint Nicholas, but I had the exact same problem today and I found a solution that at least works for Qt 4.7.4.

Setup:

A customized QGraphicsTextItem class named TextItem.

In the constructor, it gets these settings:

setFlags(ItemIsSelectable | ItemIsMovable | ItemIsFocusable);
setTextInteractionFlags(Qt::NoTextInteraction);

setFlags(ItemIsSelectable | ItemIsMovable | ItemIsFocusable);
setTextInteractionFlags(Qt::NoTextInteraction);

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This public function turns text editor mode on or off:

void SetTextInteraction(bool on, bool selectAll = false)
{
    if(on && textInteractionFlags() == Qt::NoTextInteraction)
    {
        // switch on editor mode:
        setTextInteractionFlags(Qt::TextEditorInteraction);
        // manually do what a mouse click would do else:
        setFocus(Qt::MouseFocusReason); // this gives the item keyboard focus
        setSelected(true); // this ensures that itemChange() gets called when we click out of the item
        if(selectAll) // option to select the whole text (e.g. after creation of the TextItem)
        {
            QTextCursor c = textCursor();
            c.select(QTextCursor::Document);
            setTextCursor(c);
        }
    }
    else if(!on && textInteractionFlags() == Qt::TextEditorInteraction)
    {
        // turn off editor mode:
        setTextInteractionFlags(Qt::NoTextInteraction);
        // deselect text (else it keeps gray shade):
        QTextCursor c = this->textCursor();
        c.clearSelection();
        this->setTextCursor(c);
        clearFocus();
    }
}

void SetTextInteraction(bool on, bool selectAll = false)
{
    if(on && textInteractionFlags() == Qt::NoTextInteraction)
    {
        // switch on editor mode:
        setTextInteractionFlags(Qt::TextEditorInteraction);
        // manually do what a mouse click would do else:
        setFocus(Qt::MouseFocusReason); // this gives the item keyboard focus
        setSelected(true); // this ensures that itemChange() gets called when we click out of the item
        if(selectAll) // option to select the whole text (e.g. after creation of the TextItem)
        {
            QTextCursor c = textCursor();
            c.select(QTextCursor::Document);
            setTextCursor(c);
        }
    }
    else if(!on && textInteractionFlags() == Qt::TextEditorInteraction)
    {
        // turn off editor mode:
        setTextInteractionFlags(Qt::NoTextInteraction);
        // deselect text (else it keeps gray shade):
        QTextCursor c = this->textCursor();
        c.clearSelection();
        this->setTextCursor(c);
        clearFocus();
    }
}

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Now we want to turn on the editor mode on mouseDoubleClick:

void mouseDoubleClickEvent(QGraphicsSceneMouseEvent *evt)
{
    qDebug("mouseDoubleClickEvent '%s'", this->toPlainText().toStdString().c_str());
    if(textInteractionFlags() == Qt::TextEditorInteraction)
    {
        // if editor mode is already on: pass double click events on to the editor:
        QGraphicsTextItem::mouseDoubleClickEvent(evt);
        return;
    }
 
    // if editor mode is off:
    // 1. turn editor mode on and set selected and focused:
    SetTextInteraction(true);
 
    // 2. send a single click to this QGraphicsTextItem (this will set the cursor to the mouse position):
    // create a new mouse event with the same parameters as evt
    QGraphicsSceneMouseEvent *click = new QGraphicsSceneMouseEvent(QEvent::GraphicsSceneMousePress);
    click->setButton(evt->button());
    click->setPos(evt->pos());
    QGraphicsTextItem::mousePressEvent(click);
    delete click; // don't forget to delete the event
}

void mouseDoubleClickEvent(QGraphicsSceneMouseEvent *evt)
{
    qDebug("mouseDoubleClickEvent '%s'", this->toPlainText().toStdString().c_str());
    if(textInteractionFlags() == Qt::TextEditorInteraction)
    {
        // if editor mode is already on: pass double click events on to the editor:
        QGraphicsTextItem::mouseDoubleClickEvent(evt);
        return;
    }

    // if editor mode is off:
    // 1. turn editor mode on and set selected and focused:
    SetTextInteraction(true);

    // 2. send a single click to this QGraphicsTextItem (this will set the cursor to the mouse position):
    // create a new mouse event with the same parameters as evt
    QGraphicsSceneMouseEvent *click = new QGraphicsSceneMouseEvent(QEvent::GraphicsSceneMousePress);
    click->setButton(evt->button());
    click->setPos(evt->pos());
    QGraphicsTextItem::mousePressEvent(click);
    delete click; // don't forget to delete the event
}

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To leave the editor mode, it is sufficient to wait for the deselection event:

QVariant itemChange(QGraphicsItem::GraphicsItemChange change, const QVariant &value)
{
    if(change == QGraphicsItem::ItemSelectedChange) qDebug("itemChange '%s', selected=%s", this->toPlainText().toStdString().c_str(), value.toString().toStdString().c_str());
    if(change == QGraphicsItem::ItemSelectedChange 
        && textInteractionFlags() != Qt::NoTextInteraction 
        && !value.toBool())
    {
        // item received SelectedChange event AND is in editor mode AND is about to be deselected:
        SetTextInteraction(false); // leave editor mode
    }
    return QGraphicsTextItem::itemChange(change, value);
}

QVariant itemChange(QGraphicsItem::GraphicsItemChange change, const QVariant &value)
{
    if(change == QGraphicsItem::ItemSelectedChange) qDebug("itemChange '%s', selected=%s", this->toPlainText().toStdString().c_str(), value.toString().toStdString().c_str());
    if(change == QGraphicsItem::ItemSelectedChange 
        && textInteractionFlags() != Qt::NoTextInteraction 
        && !value.toBool())
    {
        // item received SelectedChange event AND is in editor mode AND is about to be deselected:
        SetTextInteraction(false); // leave editor mode
    }
    return QGraphicsTextItem::itemChange(change, value);
}

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That's all.

I left the qDebug() outputs in the code for your convenience. :-)

Since SetTextInteraction() is public, you can call it after creating a TextItem, so the user can start typing directly (you need to make sure that the view and the scene have the keyboard focus).

[Rafe]

Thanks for this!

Here is a near-verbatim refactor to Python that runs:
(Replace YOUR_CLASS with your class)

.
    def setTextInteraction(self, state, selectAll=False):
        if state and self.textInteractionFlags() == QtCore.Qt.NoTextInteraction:
            # switch on editor mode:
            self.setTextInteractionFlags(QtCore.Qt.TextEditorInteraction)
 
            # manually do what a mouse click would do else:
            self.setFocus(QtCore.Qt.MouseFocusReason)  # give the item keyboard focus
            self.setSelected(True)  # ensure itemChange() gets called when we click out of the item
            if selectAll:  # option to select the whole text (e.g. after creation of the TextItem)
                c = self.textCursor()
                c.select(QtGui.QTextCursor.Document)
                self.setTextCursor(c)
 
        elif not state and self.textInteractionFlags() == QtCore.Qt.TextEditorInteraction:
            # turn off editor mode:
            self.setTextInteractionFlags(QtCore.Qt.NoTextInteraction)
 
            # deselect text (else it keeps gray shade):
            c = self.textCursor()
            c.clearSelection()
            self.setTextCursor(c)
            self.clearFocus()
 
    def mouseDoubleClickEvent(self, event):
        log.warn("mouseDoubleClickEvent '%s'", self.toPlainText())
 
        if self.textInteractionFlags() == QtCore.Qt.TextEditorInteraction:
            # if editor mode is already on: pass double click events on to the editor:
            super(YOUR_CLASS, self).mouseDoubleClickEvent(event)
            return
 
        # if editor mode is off:
        # 1. turn editor mode on and set selected and focused:
        self.setTextInteraction(True)
 
        # 2. send a single click to this QGraphicsTextItem (will set the cursor to the mouse pos)
        # create a mouse event with the same parameters as event
        click = QtGui.QGraphicsSceneMouseEvent(QtCore.QEvent.GraphicsSceneMousePress)
        click.setButton(event.button())
        click.setPos(event.pos())
        self.mousePressEvent(click)
 
    def itemChange(self, change, value):
        if change == QtGui.QGraphicsItem.ItemSelectedChange:
            log.warn("itemChange '%s', selected=%s", self.toPlainText(), value)
 
        if change == QtGui.QGraphicsItem.ItemSelectedChange \
            and self.textInteractionFlags() != QtCore.Qt.NoTextInteraction \
            and not value:
 
            # item received SelectedChange event AND is in editor mode AND is about to be deselected
            self.setTextInteraction(False)  # leave editor mode
 
        return super(YOUR_CLASS, self).itemChange(change, value)

.
    def setTextInteraction(self, state, selectAll=False):
        if state and self.textInteractionFlags() == QtCore.Qt.NoTextInteraction:
            # switch on editor mode:
            self.setTextInteractionFlags(QtCore.Qt.TextEditorInteraction)

            # manually do what a mouse click would do else:
            self.setFocus(QtCore.Qt.MouseFocusReason)  # give the item keyboard focus
            self.setSelected(True)  # ensure itemChange() gets called when we click out of the item
            if selectAll:  # option to select the whole text (e.g. after creation of the TextItem)
                c = self.textCursor()
                c.select(QtGui.QTextCursor.Document)
                self.setTextCursor(c)

        elif not state and self.textInteractionFlags() == QtCore.Qt.TextEditorInteraction:
            # turn off editor mode:
            self.setTextInteractionFlags(QtCore.Qt.NoTextInteraction)

            # deselect text (else it keeps gray shade):
            c = self.textCursor()
            c.clearSelection()
            self.setTextCursor(c)
            self.clearFocus()

    def mouseDoubleClickEvent(self, event):
        log.warn("mouseDoubleClickEvent '%s'", self.toPlainText())

        if self.textInteractionFlags() == QtCore.Qt.TextEditorInteraction:
            # if editor mode is already on: pass double click events on to the editor:
            super(YOUR_CLASS, self).mouseDoubleClickEvent(event)
            return

        # if editor mode is off:
        # 1. turn editor mode on and set selected and focused:
        self.setTextInteraction(True)

        # 2. send a single click to this QGraphicsTextItem (will set the cursor to the mouse pos)
        # create a mouse event with the same parameters as event
        click = QtGui.QGraphicsSceneMouseEvent(QtCore.QEvent.GraphicsSceneMousePress)
        click.setButton(event.button())
        click.setPos(event.pos())
        self.mousePressEvent(click)

    def itemChange(self, change, value):
        if change == QtGui.QGraphicsItem.ItemSelectedChange:
            log.warn("itemChange '%s', selected=%s", self.toPlainText(), value)

        if change == QtGui.QGraphicsItem.ItemSelectedChange \
            and self.textInteractionFlags() != QtCore.Qt.NoTextInteraction \
            and not value:

            # item received SelectedChange event AND is in editor mode AND is about to be deselected
            self.setTextInteraction(False)  # leave editor mode

        return super(YOUR_CLASS, self).itemChange(change, value)

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