Qt user resize event ends (stops)

Question

I have a QWidget and i need to do some actions (refresh a picture in widget) when resize event ends. How can i catch this action? I need to catch moment when user ENDs all his r

Answer 1

My Qt app uses image windows and does complex layered rebuilds, which can take some time even on a very fast machine. So not having the window redraw with every change in the window frame size was important to me so the response to the window frame resize would not be laggy.

So I solved it this way:

In my image window, I have enabled mouse tracking:

setMouseTracking(true);

Then, in the window class, I have a boolean, puntme; this is set when a resize event is caught:

bool puntme;

Then, in the mousemove event:

void imgWindow::mouseMoveEvent(QMouseEvent* event) {

if (puntme)
{
    puntme = false;
    needRebuild = true;
    update();
}

...

Basically, what this does is as soon as the user moves the mouse over the window -- which is a pretty natural thing for them to do if they were just resizing it -- then the window redraws with the new size. It doesn't happen during the resize, because Qt isn't forwarding move moves then.

Instead, during the resize, I just scale up an already existing bitmap, which gives a crude approximation of the change in scale with necessarily handling the actual newly more-or-less available resolution.

Worst case, user resizes, moves away from the window, and leaves the crudely scaled bitmap in place until the come back to it, at which point it will duly update to the actual new displayed bitmap == scale/size conditions.

There's no perfect way - what is really needed here is for Qt to provide (user has stopped resizing window" message, but in lieu of that, this has been working well for me.