Restoring session with Blastresults on macOS shows Qt error

[Zach Pearson]

When restoring a Blast session:

<QNSWindow: 0x7fe052fd40f0; contentView=<QNSView: 0x7fe052fd2dc0; QCocoaWindow(0x60000392f9c0, window=QWidgetWindow(0x600002aa4c60, name="QWidgetClassWindow"))>> has active key-value observers (KVO)! These will stop working now that the window is recreated, and will result in exceptions when the observers are removed. Break in QCocoaWindow::recreateWindowIfNeeded to debug.

is printed to the log, but the session otherwise appears to restore normally.

[Zach Pearson]

Just to note: the included session file depends on the blast_qt_gui branch.

[Tom Goddard]

Commenting out lines of code in BlastProteinResults shows that the following line causes the error

self.control_widget.setVisible(True)

And this widget is created earlier without a parent

self.control_widget = QWidget()

In general I always create widgets and pass in the parent. No telling what will go wrong if you don't specify a parent. For one, Qt will probably initially decide it is a top level window. The later when you put it into the layout of another window it will change its mind and recreate the window as a subwindow (as in the error message). So instead

parent = self.tool_window.ui_area
self.control_widget = QWidget(parent)

That eliminates the error. I suggest fixing all other Qt widgets you are creating so they specify their parent when created.

[Zach Pearson]

Thank you so much for the debugging help! I'll incorporate the necessary changes.

[goddard@…]

No trouble.  The method was to comment out all the results GUI building (no error), then add most of it back (still no error), then keep adding more and more back until I found the one line that leads to the error.  You might think that if you add widget A to the layout of widget B then B becomes the parent of A -- but that is not how Qt works.  The parent hierarchy can be anything and need not mirror which widget is laid out within which other widget -- only if you do weird stuff it often blows up.  So generally you should set the parents to mirror the layout.  If a parent is deleted then its children will be too.  If you have a weird parenting (or no parenting) then deletion does not clean up the widgets.

[Zach Pearson]

​This commit should fix it.