New class KWidgetBlendAnimation

Riccardo Iaconelli riccardo at
Fri Feb 1 20:29:05 GMT 2008

On Jan 31, 2008 9:54 PM, Matthias Kretz <kretz at> wrote:

> On Thursday 31 January 2008, Frerich Raabe wrote:
> > Hi Matthias,
> >
> > Matthias Kretz schrieb:
> > > while playing with possible UI effects I think I found a rather useful
> > > one: Fade UI changes.
> >
> > [..]
> >
> > > The class is attached. Please comment on the naming, usefulness, dox
> and
> > > whether we want to have it in kdeui for 4.1. (I want to use it in my
> > > Phonon KCM unless I can be convinced that there's a better UI hint
> than
> > > this animation).
> >
> > I didn't build your class but I just looked at the code a bit and
> wondered:
> >
> > Why do you grab a pixmap of the to-be-changed-widget in the constructor
> > (and then install an event filter on the widget so that you get all
> > paint events so you can update your pixmap)?
> >
> > Isn't it possible to just grab a pixmap within start()? Hmm, you'd need
> > to show something until start() is called. Maybe you could hide()
> > yourself, or make yourself transparent, or resize to 0x0 pixels or so?
> I tried many things but so far this is the only way to reliably get a
> pixmap
> of the updated widget. Calling grabWidget in start() gives the old pixmap,
> calling grabWidget the first time paintEvent is called also gives the old
> pixmap.
> I did not try to hide the animation widget as I don't want to have any
> flicker. The widget that gets grabbed may not draw its updated version on
> screen until the animation is over.

With Qt 4.4 you get no flickering on those hide()s. That's the alien widgets
fun. =)

> QPainter::setRedirected is pretty useless, too. It would be so easy to
> just
> redirect all paints of the original widget into the pixmap. But that
> doesn't
> work at all.

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