[Qt-interest] QEventLoop and QEvents

[Eric Clark]

> -----Original Message-----
> From: qt-interest-bounces at trolltech.com [mailto:qt-interest-
> bounces at trolltech.com] On Behalf Of Frank Hemer
> Sent: Friday, February 19, 2010 3:21 PM
> To: qt-interest at trolltech.com
> Subject: Re: [Qt-interest] QEventLoop and QEvents
> 
> On Friday 19 February 2010 20:21:07 Eric Clark wrote:
> > When I say that it is a little bit of time, it is milliseconds. This
> is how
> > it HAS to work. Without going into great detail, this particular
> widget is
> > a GLWidget. There is an active 3D simulation going on in the widget
> and
> > when you click on the widget, a 3D ray-trace is performed to find the
> 3D
> > object that was clicked on. During the active simulation, there are
> events
> > that happen that cause manipulation of the 3D objects, such as
> cutting
> > holes in the objects, or possibly removing the object from the viewer
> all
> > together. The simulation runs on a separate thread than the GUI and
> as
> > such, it is VERY unsafe to allow the ray-trace to happen while the
> > simulation is active. Instead, the 3D viewer reacts to mouse events
> when it
> > repaints. During repainting of the GLWidget, the simulation is
> temporarily
> > paused and any events that occurred between painting will also be
> > processed. Believe me, I know what I am doing as far as deferring the
> > events. The time between repaints is so fast that no user will ever
> notice
> > the delay in reaction of a mouse click. Not only that, what happens
> when
> > you click on an object is that it gets highlighted in the 3D viewer,
> this
> > highlighting would even be ok if it did take longer than normal, but
> the
> > reaction time now is on the order of milliseconds and no human eye
> can
> > possibly see the delay.
> >
> > Now that everyone knows what is really going on. I would love for
> someone
> > to answer my question. Is there any way to tell Qt to not delete the
> event?
> > Or do I need to make a copy of the event?
> 
> You can catch events (mouse and key) in an QApplication-installed
> eventHandler, store a copy and  post them later.
> That works quite well, however be aware of some surprising effects if
> for ex.
> a Window pops up right before the events get posted.
> This will most likely NOT work for other system-internal events though.

I am actually using an event handler to catch the events. That is how I defer
them. I was trying to take the event and post it to a different event loop that
I could call processEvents on when it was time to do so. However, the events
were being deleted before it was time to call processEvents on them. So, I tried to
make a copy of the event and post it to the other loop from within my event handler, but
that seemed to cause some very strange behavior. Maybe I did something wrong, I am not
sure...

Eric

> 
> Frank
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