[Qt-interest] Bug in QMdiArea or QMdiSubWindow wrt QCloseEvent under Linux but not Windows?

[Andreas Ntaflos]

On Sunday 14 June 2009 04:19:57 rajasekharan wrote:
> Andreas,
>
> What method are you using in your QMainWindow to check if all the
> sub windows of the QMdiArea are closed?

Hi, 

thank you for your reply. Like I said, the problem is (at least for 
me) reproducible on Linux by running the MDI example in 
examples/mainwindows/mdi in the Qt distribution, so my code shouldn't 
really matter, should it? 

My application uses almost exactly the same code for checking if 
exiting is ok or not:

  mdiArea->closeAllSubWindows();
  if (activeProject()) {
    event->ignore();
  } else {
    writeSettings();
    event->accept();
  }

activeProject() is like activeMdiChild() in the example:

  if (QMdiSubWindow *activeSubWindow = mdiArea->activeSubWindow())
    return qobject_cast<Project *>(activeSubWindow->widget());
  return 0;

In this instance this apparently returns 0 even when the 
activeSubWindow ignored the QCloseEvent. But it seems it only 
(falsely) returns 0 when a call to closeAllSubWindows occured, as I 
use the activeProject() method quite often throughout the main window 
code and it always works correctly.

Did you try reproducing the described behaviour with the MDI example 
application? Sidenote: I have several Qt versions installed here 
(4.4.1, 4.4.3, 4.5.0 and 4.5.1) and they all exhibit this behaviour 
in the MDI example.

> I have created an application with QMdiArea in Windows and Linux
> but didn't come across this issue. It worked correctly.
>
> In the QMainWindow's close event I used:
>
> mdiArea->closeAllSubWindows();
> if (midArea->subWindowList().size() > 0)
> {
>      closeEvent->reject();
> }
> else
> {
>      closeEvent->accept();
> }

Intersting, when using midArea->subWindowList().size() > 0 to check I 
cannot reproduce the problem anymore! It works like it should. Now I 
have at least a workaround, thank you :)

What does that mean? Probably at least that the MDI example is broken 
in that regard, but why? Why shouldn't it work as expected?

Andreas
-- 
Andreas Ntaflos 
Vienna, Austria 

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