On Wed, Sep 23, 2020 at 4:55 AM Enrico Losavio <[email protected]>
wrote:
> Hi all,
>
> I write here because I'm dealing with an issue that makes my maya crash
> all the times.
> I have found a workaround (explained later), but I'm still curious to know
> if there's a better solution.
>
> Basically I want to display some messages to the user using a modal dialog
> (QMessageBox.information()).
> I have a function (called from a ui) that is used to import a file in the
> maya scene. This is working fine.
> I also have a callback attached to that piece of ui, which is meant to
> update it (by deleting it and recreating it) every time a file is imported.
> What happens is that when I click on the Import button, the file is
> imported, the QMessageBox is shown, the code execution is paused (because
> of the modal dialog), but the callback is fired anyways.
> Since the callback deletes (and recreates) the dialog, when the code
> finally reaches the ui "self.close()" instruction, the ui object was
> already destroyed - thus resulting in a *#* *RuntimeError: Internal C++
> object **(ImportFileUI) already deleted. # *or more often than not a
> sudden maya crash.
>
>
> I temporarily avoided this error by calling the QMessageBox.show() method,
> which does not halt the execution of the code.
>
> However, rather than finding more workarounds, I would like to find a
> solution and get to the bottom of this issue.
>
>
> Does anyone have an idea of how to make the callback "wait"? Are there
> better practices to deal with a similar situation?
> I tried to delay the execution of the callback using "evalDeferred()" and
> even "processIdleEvents()", but none of them really made any difference.
>
Your example code may be oversimplified, leading to me missing your actual
intention. But based on your example it seems the question should really be
"how can I avoid the dialog widget crashing when it tries to close after
already being deleted?". If we look at the order of operations, there is
really no logical sense in trying to delay the scriptJob. It is separate
logic from the dialog which wants to happen in response to a Maya event. It
is a misconception that your modal information dialog is pausing code
execution. What it is actually doing is starting its own blocking event
loop at that point, which means the entire application can still continue
to function and process events. Only the next line in that scope of the
main thread is paused. As soon as you start the modal dialog, the new event
loop will process the scriptJob.
So now that we have addressed why the scriptJob callback still gets
executed before the end of that slot function scope, we could take a moment
to look at the suggestion of delaying the callback. If the callback is
defined outside the scope of this dialog, as in your simplified example, I
think it makes less sense to somehow try and defer it until after some
other UI logic in your dialog, because that defeats the point of the
callback. You might as well just not use the callback at all, and trigger
the create_ui function directly at the point you deem appropriate (after
the QMessageBox modal dialog has returned). But I will leave that
suggestion here for your consideration, if it makes sense to do so.
The simplest fix I can see to keeping the scriptJob callback as-is and just
preventing the close from crashing is to use deleteLater just before you
start the modal dialog:
def onBtnClicked(self):
pm.importFile(self.file_path, force=True)
self.deleteLater()
QtWidgets.QMessageBox.information(get_maya_window(), "Info",
"Scene was imported correctly")
I don't know if this approach makes sense in the scope of your actual
production code. But it fixes the issue in the simplified version. I
figured if you already intended on destroying the dialog after the
QMessageBox anyways, that this would be equivalent. If this isn't
acceptable, then maybe you can expand your example to cover something
closer to your intentions.
Justin
>
> I have put together a few lines of codes to recreate the issue, and I
> tested it in Maya 2018.7 on Windows10.
>
>
>
> from PySide2 import QtCore, QtWidgets
> from maya.OpenMayaUI import MQtUtil
> from pymel import core as pm
> from shiboken2 import wrapInstance
>
> # this code is an overly simplified version of the original script
> # its only purpose is to recreate the issue described in the post above
> # paste it the script editor, *change the ui's file_path variable to an
> existing .ma file* , and run it
> #
> # the callback destroys the ui object, before the ui.close() instruction
> can be executed
> # causing a # RuntimeError: Internal C++ object (ImportFileUI) already
> deleted. # or often even a maya crash
> # how can this be prevented?
>
> ui_name = 'ImportFileUI'
>
> def get_maya_window():
> pointer = MQtUtil.mainWindow()
> return wrapInstance(long(pointer), QtWidgets.QMainWindow)
>
> class ImportFileUI(QtWidgets.QDialog):
> def __init__(self, parent):
> super(ImportFileUI, self).__init__(parent)
> self.setObjectName(ui_name)
>
> self.file_path = r"C:\example_file.ma"
> self.btn = QtWidgets.QPushButton("Import File")
> self.btn.clicked.connect(self.onBtnClicked)
> self.setLayout(QtWidgets.QVBoxLayout())
> self.layout().addWidget(self.btn)
>
> def onBtnClicked(self):
> pm.importFile(self.file_path, force=True)
> QtWidgets.QMessageBox.information(get_maya_window(), "Info", "Scene
> was imported correctly")
> self.close()
>
> def create_ui():
> if pm.control(ui_name, exists=True):
> pm.deleteUI(ui_name)
> ui = ImportFileUI(get_maya_window())
> ui.show()
> pm.scriptJob(e=["PostSceneRead", create_ui], parent=ui_name)
>
> if __name__ == "__main__":
> create_ui()
>
>
>
> Thank you for your help!
>
>
> Enrico
>
>
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