[Bug] iOS AutoDisconnectHandler appears to be breaking layout on re-appearing modal

[brendonupson]

Description

I have a shell app (bottom tabs) which launches modal pages. When a modal page contains a SegmentedControl and a subsequent modal page is displayed then dismissed, the segmented control appears in the wrong place on the original page.

Issue only seems to affect iOS.

If I add AutoDisconnectHandler="False", the problem does NOT occur. However, if I apply this "fix" I'm unsure if there are memory leak issues.

Steps to Reproduce

1. Shell app with tabs
2. Display a modal page containing Segmented Controls
3. Push another modal page on to the stack (Merge develop into main #2 disappears but is still in the modal stack)
4. Dismiss the modal (Merge develop into main #2 re-appears)
5. Segmented Control (in Merge develop into main #2) is now in the wrong part of the page

Expected Behavior

• Page layout should remain the same

Actual Behavior

• Page layout is broken, segmented controls are pushed into the ui elements above

Basic Information

• Version with issue: 1.4.16
• Last known good version: N/A

Screenshots, Attachments, Links

[brendonupson]

[thomasgalliker]

You're absolutely right with all your assumptions. AutoDisconnectHandler="False" does not call the DisconnectHandler method in SegmentedControlHandlers (which sooner but rather later leads to memory leaks).
The problem that seems to happen here is that the handler for one of your SegmentedControls gets disconnected too soon. We have to find out what navigation scenario this is and how I can reproduce it in the sample app in this repository.

[thomasgalliker]

I'm not familiar with shell apps. Would it be possible to get a very minimal shell app which causes this problem?

[brendonupson]

The problem that seems to happen here is that the handler for one of your SegmentedControls gets disconnected too soon. We have to find out what navigation scenario this is and how I can reproduce it in the sample app in this repository.

I think the SegmentedControl is not properly checking the modal page stack, likely in HandlerCleanUpHelper.cs:
private static bool CheckIfPageIsUsed(Page targetPage)

I'll try to make a simple app to reproduce.

[thomasgalliker]

It is surely a problem is the CheckIfPageIsUsed method. The thing is, this method is growing with more scenarios :)

I wish MAUI would solve this DisconnectHandler problem for us... but at least for .net 8 they don't.

[brendonupson]

Usage:

• Click "Open Modal Page" from Tab1
• Click "Open Another Modal Page"
• Click "Close Modal Page"
• Observe broken layout. If layout is not broken, click "Open Another Modal Page" again. After a couple of times it should trigger a ui layout.

https://github.com/brendonupson/SegControlTest

[brendonupson]

[brendonupson]

Maybe just needs line 79 in HandlerCleanUpHelper.cs changed from:

return pageExists;

to:

if(pageExists) return true;

Then the code will fall through and check further?

[vhugogarcia]

Hello @brendonupson , is this PR expected to fix the layout issue with the segmented control on modal pages? #32

cc: @thomasgalliker

Thanks in advance

[thomasgalliker]

Important question: How are you registering pages in the DI container? Singleton or transient?
If you register pages and viewmodels as singleton (which I do not recommend) you have to disable to AutoDisconnectHandler feature.

[thomasgalliker]

Ok, ignore my question regarding DI registrations. I just had a look at your sample app (very valuable; always in such situations!). There is something wrong in the automatic disconnect logic. SegmentedControlHandler on Modal1Page is (mistakenly) disconnected when Modal2Page is displayed.