Circular wrapping of QListWidget items - how to?

[slscripters]

Yeah your'e right! It's a hacky solution but it makes sense. But here it is,

in the overriden keyPressEvent function,

void CustomListWidget::keyPressEvent(QKeyEvent *event)
{
   // feed this to base class as a default, we may also use this for simulating a key
   QKeyEvent *finalEvent = event;
 
   switch(finalEvent->key())
   {
     case Qt::Key_Down:
     {
        // if last item reached wrap to first
        if(currentRow() == (count()-1))
        {
           // set row to -1 so that later on doing the normal behavior it will go to row 1 which is the first item
           setCurrentRow(-1);
        } 
        break;
     }
     case Qt::Key_Up:
     {
       // if first item is reached wrap to last
       if(currentRow() == 0)
       {
          if(count() > 1)
          {
             // set the current row at the top of the last row
             setCurrentRow(count() - 2);
             // and simulate a Key_Down event, event->key() = Key_Down
             finalEvent = new QKeyEvent(copy event's values, except for key())
          }//else no need to wrap first item = last     
       }
       break;
     }
     default:
       break;
   }
 
   if(finalEvent)
  {
     // perform the normal behavior
     QListWidget::keyPressEvent(finalEvent);
  }
}

void CustomListWidget::keyPressEvent(QKeyEvent *event)
{
   // feed this to base class as a default, we may also use this for simulating a key
   QKeyEvent *finalEvent = event;
   
   switch(finalEvent->key())
   {
     case Qt::Key_Down:
     {
        // if last item reached wrap to first
        if(currentRow() == (count()-1))
        {
           // set row to -1 so that later on doing the normal behavior it will go to row 1 which is the first item
           setCurrentRow(-1);
        } 
        break;
     }
     case Qt::Key_Up:
     {
       // if first item is reached wrap to last
       if(currentRow() == 0)
       {
          if(count() > 1)
          {
             // set the current row at the top of the last row
             setCurrentRow(count() - 2);
             // and simulate a Key_Down event, event->key() = Key_Down
             finalEvent = new QKeyEvent(copy event's values, except for key())
          }//else no need to wrap first item = last     
       }
       break;
     }
     default:
       break;
   }

   if(finalEvent)
  {
     // perform the normal behavior
     QListWidget::keyPressEvent(finalEvent);
  }
}

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aamer4yu,

Does Qt automatically delete the event object ? In this case it is possible that the event object is not passed to the base class, will it still be deleted somewhere? Or do I need to explicitly delete this?

At first look, the event object may not be deleted if not passed to the base class. I hope what I'm doing is safe, I need to read more on Qt about this. Deleting the event object explicitly may even be worse. Please help.

[aamer4yu]

Why have u done extra work for key_up ??
you could have simply done as u did for key_down -
case Key_up :
if(currentRow==0)
setCurrentRow(count() -1 );

and if your conditions are not met, you can call QListWidget::keyPressEvent.
something like -

void CustomListWidget::keyPressEvent(QKeyEvent *event)
{
  bool sendEventToBaseClass = true;
   switch(event->key())
   {
       case Qt::Key_up :
              if(condition)
              {
                sendEventToBaseClass = false;
                .... // other jobs
               }
 
       break;
       case Qt::Key_Down :
              if(condition)
              {
                sendEventToBaseClass = false;
                .... // other jobs
               }
       break;
 
   } 
 
if(sendEventToBaseClass)
   QListWidget::keyPressEvent(event);
}

void CustomListWidget::keyPressEvent(QKeyEvent *event)
{
  bool sendEventToBaseClass = true;
   switch(event->key())
   {
       case Qt::Key_up :
              if(condition)
              {
                sendEventToBaseClass = false;
                .... // other jobs
               }
                  
       break;
       case Qt::Key_Down :
              if(condition)
              {
                sendEventToBaseClass = false;
                .... // other jobs
               }
       break;
       
   } 
  
if(sendEventToBaseClass)
   QListWidget::keyPressEvent(event);
}

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thats it.. no need to keep duplicate pointer...

[slscripters]

Hi,

Why have u done extra work for key_up ??

The base class's function may be setting variables or calling functions inside it to accomplish the default behavior. So I thought it would be safer to always call the base class function, anyway what I really need is just to change the current row. I've thought of creating a flag and checking if event is necessary to be passed to base class or not, like what you've done above.

I will try this and see if it works with my code. I'll go for this if this works since this is very simple solution.

With this solution, what shall we do then with the event object? Do we need to delete it explicitly after using it or not? In general, does Qt leave the deletion of the event objects to us or is it automatically deleted somewhere?