Capture mouse event on QHeaderView

[squidge]

I wish to capture mouse events on the QHeaderView part of a QTreeview. header()->installEventFilter(this); captures some events but even if the only statement in the function is "return true" (ie, filter the event), the QHeaderView still gets the mouse message.

Any ideas? I don't want to block the events, just analyse them as well.

[spirit]

show us code.

[squidge]

class FLView : public QTreeView
{
...
}
 
FLView::FLView(QWidget *parent) : QTreeView(parent) ,
{
header()->installEventFilter(this);
}
 
bool FLView::eventFilter(QObject *obj, QEvent *event)
{
return true;
}

class FLView : public QTreeView
{
...
}

FLView::FLView(QWidget *parent) : QTreeView(parent) ,
{
header()->installEventFilter(this);
}

bool FLView::eventFilter(QObject *obj, QEvent *event)
{
return true;
}

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[spirit]

try this

bool FLView::eventFilter(QObject *obj, QEvent *event)
{
return QTreeView::eventFilter(obj, event);
}

bool FLView::eventFilter(QObject *obj, QEvent *event)
{
return QTreeView::eventFilter(obj, event);
}

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[squidge]

Yes, but events I'm interested in don't get to my event filter. I can prove this by just using "return true" to attempt to block the event.

[spirit]

I didn't get: do you need to block a header's events or don't block them?

[squidge]

I wish to analyse all events passed to an object.

To see if my method of doing so worked, I attempted to ignore all the events that get passed to me so they never reach there destination. However, the control still acted as normal, handling all mouse events.

Therefore my event filter failed. Its not much of an event filter if it allows all of them through regardless.

Also, If I change the event filter code so that it pops up a messagebox when it filters an event of type "MouseButtonPress", the message box never shows up.

[squidge]

Fixed.

QHeaderView doesn't process the events directly, it gets passed from another object. Bottom line is you need to hook into the headers viewport, not the header itself.

[JoZCaVaLLo]

Hello squidge!!!

1 year and a half later somebody can still fall in this difficulty... it annoyed me during the last 2 days... it was not really obvious to find it out. Unfortunately google doesn't really look inside qtcentre.org

This is the solution that worked for me...

class MouseReleaser : public QObject
{
   Q_OBJECT
public:
   MouseReleaser(QObject * parent) : QObject(parent){;}
protected:
   bool eventFilter(QObject *obj, QEvent *ev)
   {
      if (ev->type()==QEvent::MouseButtonRelease) 
         return true;
      else 
         return QObject::eventFilter(obj, ev);
   }
};
 
...
 
MyTableView::MyTableView(QWidget *parent)
:QTableView(parent)
{
   MouseReleaser *mr = new MouseReleaser(this);
   horizontalHeader()->viewport()->installEventFilter(mr);
   verticalHeader()->viewport()->installEventFilter(mr);
}

class MouseReleaser : public QObject
{
   Q_OBJECT
public:
   MouseReleaser(QObject * parent) : QObject(parent){;}
protected:
   bool eventFilter(QObject *obj, QEvent *ev)
   {
      if (ev->type()==QEvent::MouseButtonRelease) 
         return true;
      else 
         return QObject::eventFilter(obj, ev);
   }
};

...

MyTableView::MyTableView(QWidget *parent)
:QTableView(parent)
{
   MouseReleaser *mr = new MouseReleaser(this);
   horizontalHeader()->viewport()->installEventFilter(mr);
   verticalHeader()->viewport()->installEventFilter(mr);
}

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Thank you for the great job!

[squidge]

Hello squidge!!!

1 year and a half later somebody can still fall in this difficulty... it annoyed me during the last 2 days... it was not really obvious to find it out. Unfortunately google doesn't really look inside qtcentre.org

It does if you ask it , eg: "site:qtcentre.org QHeaderView capture" brings you to this thread as first hit

[riarioriu3]

There is no direct API for this at the moment, so for the time being, you need to reimplement the mousePressEvent() [doc.qt.nokia.com] and mouseReleaseEvent() [doc.qt.nokia.com] for the headerview and check which section is being pressed on, then if it is one you want to allow to be movable, or clickable, you turn it on before calling the base implementation. In the mouseReleaseEvent() you would turn off the movable/clickable properties.

When it comes to setSortIndicatorShown() [doc.qt.nokia.com], then it is expected that the indicator will be shown until the user clicks on another section. So in mousePressEvent() we hide the indicator if the section clicked is not the one that should show the indicator. Alternatively the sort indicator can simply stay on the section clicked previously.

The example below demonstrates how this can be done.

#include <QtGui>
class HeaderView : public QHeaderView
{
    Q_OBJECT
public:
    HeaderView(QWidget *parent = 0) : QHeaderView(Qt::Horizontal, parent)
    {
        connect(this, SIGNAL(sectionClicked(int)), this, SLOT(clickedSection(int)));
    }
    void mousePressEvent(QMouseEvent *event)
    {
        if(visualIndexAt(event->pos().x()) == 1) {
            setClickable(true);
            setSortIndicator(1, sortIndicatorOrder());
            setSortIndicatorShown(true);
        } else {
            setSortIndicatorShown(false);
            resizeSection(1, sectionSize(1) - 1);
            resizeSection(1, sectionSize(1) + 1);
        }
        QHeaderView::mousePressEvent(event);
    }
    void mouseReleaseEvent(QMouseEvent *event)
    {
        QHeaderView::mouseReleaseEvent(event);
        setClickable(false);
    }
public slots:
    void clickedSection(int s)
    {
        qDebug() << "Section " << s << " clicked";
    }
};
 
class TreeWidget : public QTreeWidget
{
public:
    TreeWidget()
    {
        setColumnCount(3);
        QStringList list;
        list << "a" << "b" << "c";
        QStringList list2;
        list2 << "d" << "e" << "f";
        QTreeWidgetItem *item1 = new QTreeWidgetItem(this, list);
        QTreeWidgetItem *item2 = new QTreeWidgetItem(this, list2);
        addTopLevelItem(item1);
        addTopLevelItem(item2);
        setHeader(new HeaderView(this));
    }
};
 
#include "main.moc"
 
int main(int argc, char** argv)
{
    QApplication app(argc, argv);
    TreeWidget tree;
    tree.show();
    return app.exec();
}

#include <QtGui>
class HeaderView : public QHeaderView
{
    Q_OBJECT
public:
    HeaderView(QWidget *parent = 0) : QHeaderView(Qt::Horizontal, parent)
    {
        connect(this, SIGNAL(sectionClicked(int)), this, SLOT(clickedSection(int)));
    }
    void mousePressEvent(QMouseEvent *event)
    {
        if(visualIndexAt(event->pos().x()) == 1) {
            setClickable(true);
            setSortIndicator(1, sortIndicatorOrder());
            setSortIndicatorShown(true);
        } else {
            setSortIndicatorShown(false);
            resizeSection(1, sectionSize(1) - 1);
            resizeSection(1, sectionSize(1) + 1);
        }
        QHeaderView::mousePressEvent(event);
    }
    void mouseReleaseEvent(QMouseEvent *event)
    {
        QHeaderView::mouseReleaseEvent(event);
        setClickable(false);
    }
public slots:
    void clickedSection(int s)
    {
        qDebug() << "Section " << s << " clicked";
    }
};
 
class TreeWidget : public QTreeWidget
{
public:
    TreeWidget()
    {
        setColumnCount(3);
        QStringList list;
        list << "a" << "b" << "c";
        QStringList list2;
        list2 << "d" << "e" << "f";
        QTreeWidgetItem *item1 = new QTreeWidgetItem(this, list);
        QTreeWidgetItem *item2 = new QTreeWidgetItem(this, list2);
        addTopLevelItem(item1);
        addTopLevelItem(item2);
        setHeader(new HeaderView(this));
    }
};
 
#include "main.moc"
 
int main(int argc, char** argv)
{
    QApplication app(argc, argv);
    TreeWidget tree;
    tree.show();
    return app.exec();
}

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