Nested measure on ListView may cause duplicate items

[MartinZikmund]

Current behavior

TabView source calls UpdateLayout on one of the children of TabView. When this happens during Measure of TabListView, it causes nested call of measure, so all items are constructed twice which breaks things like selection (first item cannot be unselected). Due to the differences in control lifetime, UpdateLayout call is not needed in Uno, but the underlying issue still persists.

This may be caused by the fact that OnContainerChanging is called during the measure phase.

This problem is applicable to ListView in general, not only for TabViewListView

Expected behavior

Nested measure call should not produce duplicate set of items.

How to reproduce it (as minimally and precisely as possible)

Uncomment tabContentPresenter.UpdateLayout() in TabView.cs and debug TabViewItemsSourceTests page. Add a breakpoint in the TabViewItem constructor and observe that it is called too many times. Also notice that first item cannot be unselected - because it is in fact just a duplicate of the actual first item.

Workaround

Environment

• Uno.UI / Uno.UI.WebAssembly / Uno.UI.Skia
• Uno.WinUI / Uno.WinUI.WebAssembly / Uno.WinUI.Skia
• Uno.SourceGenerationTasks
• Uno.UI.RemoteControl / Uno.WinUI.RemoteControl
• Other:

Nuget Package Version(s):

Affected platform(s):

May be on other targets too.

• iOS
• Android
• WebAssembly
• WebAssembly renderers for Xamarin.Forms
• macOS
• Skia
  • WPF
  • GTK (Linux)
  • Tizen
• Windows
• Build tasks
• Solution Templates

IDE:

• Visual Studio 2017 (version: )
• Visual Studio 2019 (version: )
• Visual Studio for Mac (version: )
• Rider Windows (version: )
• Rider macOS (version: )
• Visual Studio Code (version: )

Relevant plugins:

• Resharper (version: )

Anything else we need to know?

[ramezgerges]

Just tested. Doesn't seem to be a problem anymore. The constructor is called exactly 4 times in the sample page and the first tab is selected (and is selectable).