Capturing composer closure in QGIS 3

Question

With QGIS 2.18, I used to capture the composer closure with PyQGIS, the class QgsComposerView and its composerViewHide signal:
self.obj_compo.composerView.composerViewHide.connect(self.raiseModule)

Now, there is the QGIS 3 answer:

AttributeError: 'composerClass' object has no attribute 'composerView'

I guess this is because "composer related methods have been removed from the public API and Python bindings. These classes have been replaced with the new layouts engine, based on QgsLayout, QgsLayoutItem, and the other related classes."
But I can't find a signal in QgsLayout class or a parent to capture the composer closure. If someone has any clues...

Ben W · Accepted Answer

The QgisInterface class has the following signals which you should be able to make work for you:
layoutDesignerClosed
layoutDesignerOpened
layoutDesignerWillBeClosed
These signals will be emitted when any print layout is opened/closed etc. but the latter two also emit the QgsLayoutDesignerInterface object which you can catch in a slot function. So, if you only want to target a specific layout you could do something like:
def layoutClosed(designer):
    if designer.window().windowTitle() == 'Some layout name':
        #Do something here

iface.layoutDesignerWillBeClosed.connect(layoutClosed)

The above is just an example which I tested in the Python console. It seems your code is inside a plugin so you will need to modify accordingly e.g. put the signal/slot connection inside the initGui(self) method, and make iface and slot function instance attribute/ method etc.
To be honest, while this should work, it doesn't seem particularly elegant but I can't readily see a better solution. If someone knows a better way- I will be glad to learn it.

Capturing composer closure in QGIS 3

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