TransitioningContentControl issue

[laolarou726]

Describe the bug

TCC will throw an exception when switch back to the old content:
Even I ensured control's Visual Parent is cleared:

I tried to write a repro but I failed to do so.

Expected behavior

Content should switch between old and new content.

Environment

• OS: Windows 11 22H2
• Avalonia-Version: 11.0.5

Additional context

Add any other context about the problem here.

[laolarou726]

Okay, I just successfully created a repro for this issue:

! There are possible photosensitive epilepsy contents, and there is a 100ms fast page switching in the repro.

https://github.com/laolarou726/TCCExceptionTest

Download and build the repro, then click the Start button, then wait for a few seconds, and the exception will pop.

[laolarou726]

It seems when I changing the content for a TCC that is inside another TCC will cause this issue. My repro has the similar structure.

[timunie]

are you setting the content directly? Imo it would be much safer to use DataTemplates instead of setting the content directly.

[laolarou726]

are you setting the content directly? Imo it would be much safer to use DataTemplates instead of setting the content directly.

But in this case it's impossible to use the DataTemplate to replace the content setting right. I'm using the TCX as the NavigationFrame here.

[laolarou726]

My current temporary solution is this:

Rewrite the Theme of the TCC like this:

<ControlTheme x:Key="{x:Type TransitioningContentControl}"
                  TargetType="TransitioningContentControl">
        <!--  Set Defaults  -->
        <Setter Property="Template">
            <ControlTemplate>
                <Panel>
                    <ContentPresenter Name="PART_ContentPresenter"
                                      Background="{TemplateBinding Background}"
                                      BorderBrush="{TemplateBinding BorderBrush}"
                                      BorderThickness="{TemplateBinding BorderThickness}"
                                      CornerRadius="{TemplateBinding CornerRadius}"
                                      ContentTemplate="{TemplateBinding ContentTemplate}"
                                      Content="{TemplateBinding Content}"
                                      Padding="{TemplateBinding Padding}"
                                      VerticalContentAlignment="{TemplateBinding VerticalContentAlignment}"
                                      HorizontalContentAlignment="{TemplateBinding HorizontalContentAlignment}" />
                    <ContentPresenter Name="PART_TransitionContentPresenter"
                                      Background="{TemplateBinding Background}"
                                      BorderBrush="{TemplateBinding BorderBrush}"
                                      BorderThickness="{TemplateBinding BorderThickness}"
                                      CornerRadius="{TemplateBinding CornerRadius}"
                                      ContentTemplate="{TemplateBinding ContentTemplate}"
                                      Padding="{TemplateBinding Padding}"
                                      VerticalContentAlignment="{TemplateBinding VerticalContentAlignment}"
                                      HorizontalContentAlignment="{TemplateBinding HorizontalContentAlignment}" />
            </Panel>
        </ControlTemplate>
    </Setter>
</ControlTheme>

Then everything will work just fine except all the transition animations will be loss. But the page switch will be fine.

[laolarou726]

@timunie @MrJul Does this bug have anything to do with this PR #12173？

[timunie]

Could be, yeah. If you test a release just before that PR was merged, is the issue resolved?

I don't know what a proper solution would be. The TCC is kind of nightmare to me 😃

/cc @danielmayost

[laolarou726]

Could be, yeah. If you test a release just before that PR was merged, is the issue resolved?

I don't know what a proper solution would be. The TCC is kind of nightmare to me 😃

/cc @danielmayost

Just created a PR to fix this issue, it should be good right now. #13518