how can move up/down the cursor after QComboBox showPopup?

[josentop]

when my QComboBox show popup the list, it is default to use UP/DOWN key to select, i need to change UP/DOWN key to LEFT/RIGHT key to select, i try to use the eventFilter in my QComboBox, but seem it is impossible due to i can't access the moveCursor function.
could you give me your suggestion? thanks.

[Lykurg]

Why do you need to move the cursor? Just eat the key up and down events and send them if key left right is clicked. Or Subclass QComboBox and reimp QComboBox::keyPressEvent().

[josentop]

Hi,
i need to move up/down the cursor in the below item list popup from ComboBox. Is it still possible to reimplement QComboBox's keyPressEvent? thanks.

lpp.png

[Lykurg]

With cursor you mean selection? If so:

void MyComboBox::keyPressEvent(QKeyEvent* e)
{
  if (Qt::Key_Up == e->key()
      || Qt::Key_Down == e->key())
    return;
 
  if (Qt::Key_Left == e->key())
  {
    QKeyEvent myEvent(QEvent::KeyPress, Qt::Key_Up, Qt::NoModifier);
    QComboBox::keyPressEvent(&myEvent);
  }
  else if (Qt::Key_Right == e->key())
  {
    QKeyEvent myEvent(QEvent::KeyPress, Qt::Key_Down, Qt::NoModifier);
    QComboBox::keyPressEvent(&myEvent);
  }
  else
  {
    QComboBox::keyPressEvent(e);
  }
}

void MyComboBox::keyPressEvent(QKeyEvent* e)
{
  if (Qt::Key_Up == e->key()
      || Qt::Key_Down == e->key())
    return;

  if (Qt::Key_Left == e->key())
  {
    QKeyEvent myEvent(QEvent::KeyPress, Qt::Key_Up, Qt::NoModifier);
    QComboBox::keyPressEvent(&myEvent);
  }
  else if (Qt::Key_Right == e->key())
  {
    QKeyEvent myEvent(QEvent::KeyPress, Qt::Key_Down, Qt::NoModifier);
    QComboBox::keyPressEvent(&myEvent);
  }
  else
  {
    QComboBox::keyPressEvent(e);
  }
}

To copy to clipboard, switch view to plain text mode 

EDIT: If you need to move the selection while the popup is shown, you have to install an event filter on QCombobox::view() in your subclass.

[josentop]

With cursor you mean selection? If so:

void MyComboBox::keyPressEvent(QKeyEvent* e)
{
  if (Qt::Key_Up == e->key()
      || Qt::Key_Down == e->key())
    return;
 
  if (Qt::Key_Left == e->key())
  {
    QKeyEvent myEvent(QEvent::KeyPress, Qt::Key_Up, Qt::NoModifier);
    QComboBox::keyPressEvent(&myEvent);
  }
  else if (Qt::Key_Right == e->key())
  {
    QKeyEvent myEvent(QEvent::KeyPress, Qt::Key_Down, Qt::NoModifier);
    QComboBox::keyPressEvent(&myEvent);
  }
  else
  {
    QComboBox::keyPressEvent(e);
  }
}

void MyComboBox::keyPressEvent(QKeyEvent* e)
{
  if (Qt::Key_Up == e->key()
      || Qt::Key_Down == e->key())
    return;

  if (Qt::Key_Left == e->key())
  {
    QKeyEvent myEvent(QEvent::KeyPress, Qt::Key_Up, Qt::NoModifier);
    QComboBox::keyPressEvent(&myEvent);
  }
  else if (Qt::Key_Right == e->key())
  {
    QKeyEvent myEvent(QEvent::KeyPress, Qt::Key_Down, Qt::NoModifier);
    QComboBox::keyPressEvent(&myEvent);
  }
  else
  {
    QComboBox::keyPressEvent(e);
  }
}

To copy to clipboard, switch view to plain text mode 

EDIT: If you need to move the selection while the popup is shown, you have to install an event filter on QCombobox::view() in your subclass.

but my really problem is how to implement the event filter for QCpmboBox::view(). Could you please give more detail about it? thanks.

[Lykurg]

It's quite the same as above. Subclass QComboBox and install the filter there. An I still don't get what you really want. Move the selection on the popup up and down with the left and right arrows? And what do you have so far?

[josentop]

Yes, please see below my detail wants: after user selected the comboBox, he can use Key_Alt to popup the item list view. and then he can use the left/right arrow key to select the item in the list, then use Key_Alt key to confirm the selected item and close the item list view. I have implement the below code, but seem the even filter for QComboBox's view() doesn't work.

#include "combobox.h"
 
#include <QEvent>
#include <QKeyEvent>
#include <QAbstractItemView>
#include <QDebug>
 
ComboBox::ComboBox(QWidget *parent) :
    QComboBox(parent)
{
    view()->installEventFilter(this);
}
 
void ComboBox::keyPressEvent(QKeyEvent *e)
{
    if (e->key() == Qt::Key_Space) return;
 
    int key = Qt::Key_unknown;
    if (e->key() == Qt::Key_Alt || e->key() == Qt::Key_Meta) key = Qt::Key_Space;
 
    if (key == Qt::Key_unknown) QComboBox::keyPressEvent(e);
    else
    {
        QKeyEvent myEvent(QEvent::KeyPress, key, Qt::NoModifier);
        QComboBox::keyPressEvent(&myEvent);
    }
}
 
bool ComboBox::eventFilter(QObject *t, QEvent *e)
{
	if(e->type() == QEvent::KeyPress)
	{
		QKeyEvent *keyEvent = static_cast<QKeyEvent*>(e);
		int key = keyEvent->key();
 
		qDebug("Key = %x", key);
 
		int key_map = Qt::Key_unknown;
		if (t == (QObject *)view())
		{
			switch(key)
			{
			case Qt::Key_Left:
				key_map = Qt::Key_Up;
				break;
			case Qt::Key_Right:
				key_map = Qt::Key_Down;
				break;
			case Qt::Key_Alt:
			case Qt::Key_Meta:
				break;
			case Qt::Key_Space:
				break;
			}
		}
 
		if (key_map != Qt::Key_unknown)
		{
			QKeyEvent myEvent(QEvent::KeyPress, key_map, Qt::NoModifier);
			return QComboBox::eventFilter(t, &myEvent);
		}
	}
	return QComboBox::eventFilter(t, e);
}

#include "combobox.h"

#include <QEvent>
#include <QKeyEvent>
#include <QAbstractItemView>
#include <QDebug>

ComboBox::ComboBox(QWidget *parent) :
    QComboBox(parent)
{
    view()->installEventFilter(this);
}

void ComboBox::keyPressEvent(QKeyEvent *e)
{
    if (e->key() == Qt::Key_Space) return;

    int key = Qt::Key_unknown;
    if (e->key() == Qt::Key_Alt || e->key() == Qt::Key_Meta) key = Qt::Key_Space;

    if (key == Qt::Key_unknown) QComboBox::keyPressEvent(e);
    else
    {
        QKeyEvent myEvent(QEvent::KeyPress, key, Qt::NoModifier);
        QComboBox::keyPressEvent(&myEvent);
    }
}

bool ComboBox::eventFilter(QObject *t, QEvent *e)
{
	if(e->type() == QEvent::KeyPress)
	{
		QKeyEvent *keyEvent = static_cast<QKeyEvent*>(e);
		int key = keyEvent->key();

		qDebug("Key = %x", key);

		int key_map = Qt::Key_unknown;
		if (t == (QObject *)view())
		{
			switch(key)
			{
			case Qt::Key_Left:
				key_map = Qt::Key_Up;
				break;
			case Qt::Key_Right:
				key_map = Qt::Key_Down;
				break;
			case Qt::Key_Alt:
			case Qt::Key_Meta:
				break;
			case Qt::Key_Space:
				break;
			}
		}

		if (key_map != Qt::Key_unknown)
		{
			QKeyEvent myEvent(QEvent::KeyPress, key_map, Qt::NoModifier);
			return QComboBox::eventFilter(t, &myEvent);
		}
	}
	return QComboBox::eventFilter(t, e);
}

To copy to clipboard, switch view to plain text mode 

[Lykurg]

Hi,

you have to use e.g.

return QApplication::sendEvent(t, &myEvent);

return QApplication::sendEvent(t, &myEvent);

To copy to clipboard, switch view to plain text mode 

.

[josentop]

Hi Lykurg,
It works well after applied the modification. thanks very much.