QLineEdit could not set shortcuts when it's in focus

Question

I'm implementing a text-based to-do program. I have a CommandInput widget which inherits from QLineEdit . Basically there are a few commands, starting with keywords "add", "delete", "edit", and a few more.

I want to implement a few shortcuts.

1. Ctrl+A so that when the widget has focus, I can setText("add \"\"") , cursor at the second last position, so it appears to be add "|"
2. Tab so that when the widget has focus, when the user types in the first keyword, for example, add , then I can complete the command to add "|"

The key problem is that when the widget has focus, the shortcuts are not working. I've tried the following ways:

1/ Override keyPressEvent . The Tab key does not work as intended. And even if it works, I don't know how to do that for a keySequence like Ctrl+A .

void CommandInput::keyPressEvent(QKeyEvent *keyEvent)

{
    switch(keyEvent->key())
    {
    case Qt::Key_Tab;
        emit add_activated();
    default:
        QLineEdit::keyPressEvent(keyEvent);
    }
}

2/ Create shortcuts when initializing. This doesn't work either.

CommandInput::CommandInput(QWidget *parent)
    : QLineEdit(parent)
{
    tab_shortcut = new QShortcut(QKeySequence("Tab"),this);
    add_shortcut = new QShortcut(QKeySequence("Ctrl+A"),this);

    connect(tab_shortcut, SIGNAL(activated()),
            this, SIGNAL(tab_activated()));
    connect(add_shortcut, SIGNAL(activated()),
            this, SIGNAL(add_activated()));
}

Hope you could help me on this issue. Thanks!

Answer 1

Overriding keyPressEvent is probably the preferred approach here. I'm going to guess that the reason why "Tab" doesn't work as expected is because you don't have a break statement after emitting add_activated() . For "Ctrl+A", you'll have to look at the modifiers() for the key event. As such, your keyPressEvent would look something like this:

void CommandInput::keyPressEvent(QKeyEvent* keyEvent)
{
   if (keyEvent->key() == Qt::Key_Tab)
   {
      emit add_activated();
   }
   else if (keyEvent->key() == Qt::Key_A && 
            keyEvent->modifiers() == Qt::ControlModifier)
   {
      // Code for Ctrl+A goes here.
   }
   else
   {
      QLineEdit::keyPressEvent(keyEvent);
   }
}

This seems to work on my (Linux) machine.

Answer 2

In order to get the Tab key working, I had to catch the keyPressEvent within event(), like this:

bool MyQTextBox::event(QEvent* event) {
    if (event->type() == QEvent::KeyPress) { // this did the trick for me
        this->keyPressEvent(dynamic_cast<QKeyEvent*>(event));
        return true;
    }
    return QWidget::event(event);
}