[Qt-interest] Aspect Ratio with QWidget::heightForWidth(int)

[Huseyin Kozan]

Thank you for the reply David.
I did another way before this try like this:

void MainWindow::resizeEvent(QResizeEvent * event)
{
        resizeSessionWidget();
}

/** Resize sessionWidget to keep aspect ratio. */
void MainWindow::resizeSessionWidget(void)
{
    double ratio = 1.4;
    int w = sessionWidget->width();
    int h = sessionWidget->height();
    int calc_h = h ;
    int calc_w = h * ratio;
    if (calc_w > w ) {
        calc_w = w;
        calc_h = w / ratio;
    }
    sessionWidget->resize(calc_w, calc_h);
}

/** Resizing process with delay. */
void MainWindow::resizeSWWithDelay(void)
{
    QTimer::singleShot(0, this, SLOT(resizeSessionWidget()));
}

I have some trouble with this design. When resizing, no problem. but when I
show or hide some ather widgets I need to resize it with delay. It is so
irritating to think about all possible resize needs at the run time.

I remember that there is another way do it with the layouts. That mentioned
in here :
http://stackoverflow.com/questions/452333/how-to-maintain-widgets-aspect-ratio-in-qt
But it seems so hard to do it. Maybe I can try this later time.


Hüseyin


On Wed, Jul 22, 2009 at 18:06, David Boddie <david.boddie at nokia.com> wrote:

> Huseyin Kozan wrote:
>
> > On Wed, Jul 22, 2009 at 13:37, David Boddie <david.boddie at nokia.com>
> > wrote:
>
> > Is this sizeHint() thing for initial size ?
>
> Yes. I thought it might influence the height-for-width behavior, but I was
> mistaken. What you are doing should be correct. However, the height
> returned
> by the heightForWidth() function is not treated as an absolute requirement
> for the size of your widget - the layout won't push other widgets out of
> the way to make room for your widget.
>
> > But I cannot see the difference. What is the requirements for layouting
> > parents and childs ? I mean we cannot force the main window to maintain
> > the ratio, and do I need to add spacers near the promoted widget, and/or
> > child widgets ?
>
> You may be able to achieve something like what you want by giving your
> widget a vertical size policy that lets it expand (Expanding) while giving
> other widgets in the layout policies (or stretch factors) that ensure that
> they stay out of the way. Even with these, the window's own size is a
> constraint you can't override.
>
> Another technique for ensuring that some content always has a particular
> shape is to resize and position it within a widget. So, you look at how
> much space you have and draw the desired shape, leaving the surrounding
> area blank. There may be ways to ensure that a standard widget has a
> certain shape, but that would require a bit more thought on my part.
>
> David
> --
> David Boddie
> Senior Technical Writer
> Nokia, Qt Software
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