Mahapps.metro: TabItem HeaderFontSize change leads to freeze

[seb30]

Hello,

I encountered in a problem on some PCs by using the _MetroTabItem_ and try to resize the _HeaderFontSize_ with _ControlsHelper.HeaderFontSize_. This works on most of the user PCs, but some users notified me about a freeze of the application. I tried then to reproduce the issue and my Microsoft Surface 3 Pro behaves in the same way.

The next screen capture shows a sample application with some _TabItems_ and _HeaderFontSize_ set to 15:

And again, but with _HeaderFontSize_ set to 14. As you can see, no main window opens and the CPU load goes up to 100% on a core:

• MahApps.Metro version 1.6.5
• OS: Win10 1803
• Visual Studio 2017 15.8.0
• .NET Framework 4.7.2

My sample application is attached.

TabItemTest_Git.zip

[Anapher]

I just downloaded your application and tested it on my PC and I cannot reproduce this behavior (it starts normally, Debug aswell as Release). Does that also occure when starting from VS? Anyways, can you try to attach a debugger to see what's happening?

[seb30]

Hey @Anapher,

The behavior also didn't occur on my development PC, but at my Surface and some other (mobile) devices. The attached debugger shows nothing special, only a high CPU load like the task manager.

[Anapher]

Sorry, I cannot help you here as I don't have access to a surface :/ but that is really odd and if reproducible, a huge problem

[seb30]

The issue also may occur on Laptops.

[punker76]

@seb30 I can reproduce this with targeting .Net 4.7.1 and 4.7.2. If I use 4.6.x and 4.5.x then all works fine. That's crazy...

/cc @batzen do you have any suggestion on this issue?

[batzen]

Will have a look at this.

[seb30]

@batzen Please let me know if I can support you.

Btw, it also happens with HeaderFontSize set to 17 or 19 (can't try now).

[batzen]

Tried to reproduce, but can't.
@punker76 were you able to repro this on your dev machine? I only have my dev machine at hand...

[punker76]

@seb30 Got it #3319

/cc @batzen

[seb30]

@punker76 Good work! But why this doesn't affect the FrameworkElement if HeaderFontSize is set to 15?

[punker76]

@seb30 I really don't know :-(

[kblohm]

This might be related to https://github.com/Microsoft/dotnet/issues/604. Setting

<AppContextSwitchOverrides value="Switch.System.Windows.Controls.Grid.StarDefinitionsCanExceedAvailableSpace=true" />

fixed the issue for us.