Properly unsubscribe when property page is removed

[amolenaar]

PR Type

What kind of change does this PR introduce?

• Bug fix
• Feature
• Chore (refactoring, formatting, local variables, other cleanup)
• Documentation content changes

What is the current behavior?

Event handlers "leak" in GTK 4.

Issue Number: N/A

What is the new behavior?

Add a function to unsubscribe watchers. It appeared handlers were not properly removed in GTK4, since in GTK4 widgets are not "destroyed", but only use reference counting.

Information

Added a function to gaphor.diagram.propertypages to unsubscribe automatically on widget destroy (gtk3) or unparent (gtk4).

[sourcery-ai]

Sourcery Code Quality Report

✅  Merging this PR will increase code quality in the affected files by 0.19%.

Quality metrics	Before	After	Change
Complexity	2.99 ⭐	2.98 ⭐	-0.01 👍
Method Length	47.97 ⭐	47.66 ⭐	-0.31 👍
Working memory	3.95 ⭐	3.97 ⭐	0.02 👎
Quality	77.90% ⭐	78.09% ⭐	0.19% 👍

Other metrics	Before	After	Change
Lines	1693	1726	33

Changed files	Quality Before	Quality After	Quality Change
gaphor/C4Model/propertypages.py	86.86% ⭐	87.23% ⭐	0.37% 👍
gaphor/SysML/propertypages.py	78.47% ⭐	78.52% ⭐	0.05% 👍
gaphor/UML/actions/actionspropertypages.py	85.44% ⭐	85.57% ⭐	0.13% 👍
gaphor/UML/actions/activitypropertypage.py	78.00% ⭐	78.04% ⭐	0.04% 👍
gaphor/UML/classes/associationpropertypages.py	67.34% 🙂	67.37% 🙂	0.03% 👍
gaphor/UML/classes/classespropertypages.py	73.07% 🙂	73.13% 🙂	0.06% 👍
gaphor/UML/classes/dependencypropertypages.py	87.65% ⭐	87.62% ⭐	-0.03% 👎
gaphor/UML/classes/enumerationpropertypages.py	61.94% 🙂	62.08% 🙂	0.14% 👍
gaphor/UML/profiles/metaclasspropertypage.py	77.95% ⭐	78.02% ⭐	0.07% 👍
gaphor/UML/states/propertypages.py	80.99% ⭐	81.12% ⭐	0.13% 👍
gaphor/diagram/propertypages.py	84.44% ⭐	84.66% ⭐	0.22% 👍
gaphor/diagram/general/generalpropertypages.py	75.45% ⭐	76.64% ⭐	1.19% 👍

Here are some functions in these files that still need a tune-up:

File	Function	Complexity	Length	Working Memory	Quality	Recommendation
gaphor/UML/classes/classespropertypages.py	OperationsPage.construct	10 🙂	270 ⛔		42.35% 😞	Try splitting into smaller methods
gaphor/UML/classes/classespropertypages.py	AttributesPage.construct	10 🙂	261 ⛔		42.95% 😞	Try splitting into smaller methods
gaphor/UML/classes/associationpropertypages.py	AssociationPropertyPage.construct	7 ⭐	296 ⛔		45.07% 😞	Try splitting into smaller methods
gaphor/UML/classes/enumerationpropertypages.py	EnumerationPage.construct	10 🙂	208 ⛔		47.57% 😞	Try splitting into smaller methods
gaphor/SysML/propertypages.py	ItemFlowPropertyPage.construct	7 ⭐	219 ⛔	8 🙂	54.44% 🙂	Try splitting into smaller methods

Legend and Explanation

The emojis denote the absolute quality of the code:

• ⭐ excellent
• 🙂 good
• 😞 poor
• ⛔ very poor

The 👍 and 👎 indicate whether the quality has improved or gotten worse with this pull request.

---

Please see our documentation here for details on how these metrics are calculated.

We are actively working on this report - lots more documentation and extra metrics to come!

Help us improve this quality report!

[danyeaw]

This looks great! How did you figure out that GTK4 event handlers were leaking?

[amolenaar]

I know something changed in the way widgets are destroyed. Initially I just made it work (not break), but forgot to come back and fix it for real.