[EVENT COMPRESSION 4.7.1 VS 5.3.0]

avogad

Hi,

Seems like event compression has change between versions 4.7.1 and 5.3.0.

I've implemented a basic widget that handles mouse move events and process some code in it.
Here is a basic example of what it looks like. (no matter what the function does)

@void MyLabel::mouseMoveEvent(QMouseEvent* /event/)
{
//do something long
int k = 1;
for(int i = 0; i < 100000000; ++i)
{
k = sqrt(k) + sqrt(k) + sqrt(k);
}
this->setText(QString::number(++_nb));
}@

The same code has been compiled using both version 4.7.1 and 5.3.0.

Version 4.7.1 seems to properly compress events as the event is treated a few time while I click and move the mouse on the widget but 5.3.0 seems to treat every events so I have to wait to get any feedback.

Is their an explanation to that change and is there a way to get a proper event compression?

Thanks

SGaist

Hi and welcome to devnet,

I remember reading some posts about the mouse event handling having changed but IIRC it was more about the handling of the clicked/double clicked events.

Anyway, from a pure design point of view, having long operations taking place in a mouse event (or events in general) is not a good idea. Triggering a long operation from an event handler in a secondary thread is OK though

avogad

Hi SGaist,

Thanks for answering.

The long operation was just an example to highlight the difference between both versions.

The thing is that sometimes, one need to precisely track the mouse, like a drawing operation in a paint software, but sometimes the final result is the only thing needed, then avoiding in-between events is not an issue.

SGaist

I see what you mean. To discuss difference of implementation between Qt 4 and Qt 5's event compression, you should contact the interest mailing list. You'll find there Qt's developers/maintainers. This forum is more user oriented.