[Interest] Calling QMainWindow::close() vs. clicking on close button in title bar

[John Weeks]

Our application needs to control how windows close pretty carefully- we handle QEvent::close by ignoring it, then doing whatever we feel like we need to do. That is, we take over management of the situation.

-John Weeks
WaveMetrics, Inc.

> On Oct 30, 2018, at 5:53 AM, Andy <asmaloney at gmail.com> wrote:
> 
> Turns out that if you have a QMainWindow containing a QWindow (e.g. by using QWidget::createWindowContainer()):
> 
>   - if you call QMainWindow::close(), the QWindow receives QEvent::Hide and does the right thing
>   - if you click the close button in the title bar, the QWindow receives QEvent::Close which calls QWindow::destroy()
> 
> This is not what I would expect. Is this by design?
> 
> The QWidget::createWindowContainer docs don't mention this as a limitation.
> 
> I haven't yet found a way around it, so suggestions appreciated.
> 
> ---
> Andy Maloney  //  https://asmaloney.com
> twitter ~ @asmaloney
> 
> 
> On Tue, Oct 30, 2018 at 7:24 AM Andy <asmaloney at gmail.com> wrote:
> Setup:
> 
> - two QMainWindows - "main" and "viewer"
> - "viewer" uses Qt3D via QWidget::createWindowContainer()
> - shortcut "cmd-w" (Qt::ApplicationShortcut) set up to call close() on "viewer" if it is the activeWindow()
> - "viewer" does not have WA_DeleteOnClose set, so the window is only hidden
> 
> Problem:
> 
> - if I close the viewer via the shortcut and reopen it, the 3D view is fine
> - if I close it via the close button in the title bar (macOS or Windows) and reopen it, the 3D view is blank
> 
> Any idea why my 3D view is getting killed in the second case?
> 
> This may be a red-herring, but I've traced both through to QWidgetPrivate::close_helper() and each is called with a different mode. The first is called with "CloseWithEvent" and the second with "CloseWithSpontaneousEvent". Could this be a factor?
> 
> I have another window which uses a QGraphicsView set up exactly the same way and it works fine, so maybe Qt3D is doing something I'm not expecting based on a CloseWithSpontaneousEvent?
> 
> Thanks for any ideas/suggestions.
> 
> ---
> Andy Maloney  //  https://asmaloney.com
> twitter ~ @asmaloney
> 
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-John