keypressEventFilter() to accept Enter and Return Tab

[ad5xj]

I have a keypressEventFilter on a textedit box in order to trap the Return or Enter key press. This part works great. I then wish to continue the event returning a Tab instead.

The documentation talks about it -
"(Sometimes in data-entry applications Enter does the same as Tab; this can easily be achieved in Qt by implementing an event filter.) " ,

but there is no example or other documentation to explain how to change the the key press from Qt::Key_Enter to Qt::Key_Tab. There is only the generic "// special tab handling here" comment where code should be to illustrate what the text has already given as an example.

I thought I could return the Qt:Key_Tab value but the return must be an event not a value. I don't think issuing another keypress with the QKeyPress or QEvent is right, so what is appropriate for this situation?

[jpn]

Perhaps I overlooked something but I think you might have just found a bug in the docs. The described behaviour is fairly possible with QWidget::focusNextPrevChild() BUT it's protected so actually one needs to reimplement the key press event handler, not to install an event filter:

myTextEdit->setTabChangesFocus(true);
 
void MyTextEdit::keyPressEvent(QKeyEvent* event)
{
	if (event->key() == Qt::Key_Return)
	{
		focusNextPrevChild(true);
	}
	else
	{
		QTextEdit::keyPressEvent(event);
	}
}

myTextEdit->setTabChangesFocus(true);

void MyTextEdit::keyPressEvent(QKeyEvent* event)
{
	if (event->key() == Qt::Key_Return)
	{
		focusNextPrevChild(true);
	}
	else
	{
		QTextEdit::keyPressEvent(event);
	}
}

To copy to clipboard, switch view to plain text mode 

[ad5xj]

Implementing your code in this way is not the whole story is it? I mean this code:

void txtName::keyPressEvent(QKeyEvent* event)
{
if (event->key() == Qt::Key_Return))
{
focusNextPrevChild(true);
}
else
{
QTextEdit::keyPressEvent(event);
}
}


causes an error because it does not know that txtName is an object on my MainWindow. - "Error:Undeclared first use". Plus the focusNextPrevChild(true) statement draws an error that is similar. What am I missing?

[jpn]

What you need is a QTextEdit subclass:

class MyTextEdit : public QTextEdit
{
public:
   ...
protected:
   void keyPressEvent(QKeyEvent* event);
   ...
};

class MyTextEdit : public QTextEdit
{
public:
   ...
protected:
   void keyPressEvent(QKeyEvent* event);
   ...
};

To copy to clipboard, switch view to plain text mode 

[ad5xj]

Ok, the TextEdit is subclassed and now it does not show up on my MainForm. It is in a QFrame container. If I issue a show() it is a separate window and the setTabOrder() gives a debug message about two different windows. Whatz up with that?

[marcel]

I don't know. Probably something wrong in other part of the code. Can you post it?

[joshlareau]

Has anyone considered using the QShortcut class to handle intercepting keyboard shortcuts? I had a table widget that was "stealing" the enter and tab keys from me and I got around the problem by using QShortCut as follows:

//Intercept the CTRL-TAB key from the table widget
QShortcut* shortcutTabKey;
shortcutTabKey = new QShortcut( QKeySequence( tr("Ctrl+TAB") ), m_tableWidget );
connect( shortcutTabKey, SIGNAL( activated() ), this, SLOT( OnTableShortCutTabKey() ) );

Hopefully this helps someone, as it seems easier than overriding QWidget::event.

[macias]

The documentation talks about it -
"(Sometimes in data-entry applications Enter does the same as Tab; this can easily be achieved in Qt by implementing an event filter.) " ,

This is quite opposite to what you want to achieve. In your case you have to kill filter because it is already installed -- read about tab handling, it is a special key for focus switching.

have a nice day, bye

[Michiel]

It might be as simple as this (event filter function frame taken from the docs):

bool FilterObject::eventFilter(QObject *object, QEvent *event)
 {
     if (object == target && event->type() == QEvent::KeyPress) {
         QKeyEvent *keyEvent = static_cast<QKeyEvent *>(event);
         if (keyEvent->key() == Qt::Key_Enter) {
             *keyEvent = QKeyEvent(Qt::Key_Tab);
         }
     }
     return false;
 }

bool FilterObject::eventFilter(QObject *object, QEvent *event)
 {
     if (object == target && event->type() == QEvent::KeyPress) {
         QKeyEvent *keyEvent = static_cast<QKeyEvent *>(event);
         if (keyEvent->key() == Qt::Key_Enter) {
             *keyEvent = QKeyEvent(Qt::Key_Tab);
         }
     }
     return false;
 }

To copy to clipboard, switch view to plain text mode 

Seems that the QKeyEvent lacks a setKey() function. But I'd think the event parameter is not non-const for nothing.