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List:       kde-core-devel
Subject:    Mousewheel orientation of KIconView in TopToBottom mode
From:       Wilco Greven <greven () kde ! org>
Date:       2002-01-18 0:38:25
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Hi,

I'd like to change the direction in which KIconView scrolls by using the 
mousewheel in TopToBottom mode. Because there usually is only a horizontal
scrollbar in TopToBottom mode, it makes sense IMO to make the mousewheel 
scroll horizontally instead of vertically by default (only in TopToBottom 
mode of course). Examples where this behaviour is very useful are konq's 
MultiColumn view, and in the short view of the filedialog.

One needs to reimplement KIconView::wheelEvent to make this work. AFAIKS there 
are two possibilities. The simplest one is as follows: 

void KIconView::wheelEvent( QWheelEvent *e )
{
    if( arrangement() == TopToBottom && e->orientation() == Vertical ) {
        QWheelEvent ne( e->pos(), e->delta(), e->state(), Horizontal );
        QIconView::wheelEvent( &ne );
    }
    else
        QIconView::wheelEvent( e );
}

The problem with the above reimplementation is that the new wheelevent with 
the changed orientation is passed to viewportWheelEvent. This can be avoid by 
taking QScrollView::wheelEvent, and switch the orientation after 
viewportWheelEvent has been called.

void KIconView::wheelEvent( QWheelEvent *e )
{
    QWheelEvent ce( viewport()->mapFromGlobal( e->globalPos() ),
                    e->globalPos(), e->delta(), e->state());
    viewportWheelEvent(&ce);

    -- Switch orientation here --

    if ( !ce.isAccepted() ) {
        if ( e->orientation() == Horizontal && horizontalScrollBar() )
            QApplication::sendEvent( horizontalScrollBar(), e);
        else  if (e->orientation() == Vertical && verticalScrollBar() )
            QApplication::sendEvent( verticalScrollBar(), e);
    }
}

Greetings,
Wilco
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