Question

I understand that in Qt4, there is no single flag you can set to have the mouse driven resizing of the window maintain a certain aspect ratio (say, 1:1). Is there a way to force a new size for the window while in “resizeEvent (QResizeEvent * event)”? the parameters of the event don’t seem to support change or give the user a chance to inject a new size.

My goal: GUI/Mouse resizing of a certain window will maintain its current aspect ratio, regardless of where you resize it from (sides, top, bottom, corners).

Answer 1

Duplicate Question?
How to maintain widgets aspect ratio in Qt?

Citing the answer by ‘df’ in the above link

Calling resize() from within resizeEvent() has never worked well for
me — at best it will cause flickering as the window is resized twice
(as you have), at worst an infinite loop.

I think the “correct” way to maintain a fixed aspect ratio is to
create a custom layout. You’ll have to override just two methods,
QLayoutItem::hasHeightForWidth() and QLayoutItem::heightForWidth().

Also checkout Sam Dutton’s solution @ http://lists.trolltech.com/qt-interest/2007-01/msg00204.html

void MyWindow::resizeEvent(QResizeEvent * /*resizeEvent*/) 
{
    int containerWidth = _myContainerWidget->width();
    int containerHeight = _myContainerWidget->height();

    int contentsHeight = containerHeight ;
    int contentsWidth = containerHeight * _aspectRatio;
    if (contentsWidth > containerWidth ) {
        contentsWidth = containerWidth ;
        contentsHeight = containerWidth / _aspectRatio;
    }

    resizeContents(contentsWidth, contentsHeight);
}