TabView border disappears when there is a single tab only

[cricketthomas]

Describe the bug When using the TabView component, the border to the right of the tab disappears if there is just one item in the TabView list. Not sure if this is intentional or not, it can easily be styled. That being said, the right border arc does disappear when the tab is empty.

<Style Selector="ui|TabView /template/ ContentPresenter">
      <Setter Property="BorderBrush">
          <Setter.Value>
              <SolidColorBrush Opacity="1" Color="{DynamicResource TabViewBorderBrush}" />
          </Setter.Value>
      </Setter>
      <Setter Property="BorderThickness" Value="0,0,0,1" />
  </Style>

Border visible on multiple tabs:

Border gone when there's a single tabview item:

Desktop/Platform:

• OS: Windows 11
• FluentAvalonia Version 2.1.0 and current
• Avalonia Version 11.1.0-beta1

[amwx]

Definitely a bug, probably missing a resource somewhere. WinUI:

[robloo]

The border is also missing in your first image.

The issue appears to be that this part of the border is part of the non-selected tab style itself.

[cricketthomas]

It also seems to be the same with front of the tab missing the border if you add margin to the front of the tabs or whitespace with TabStripHeader=" ". I've been trying to fix it in the source, but I am really new to Avalonia.

[amwx]

Issue has been fixed*

Two issues: 1- Avalonia for some reason won't render a 1px height Border, so that wasn't even rendering. Rectangle works fine, so these elements were changed to that (which may even be a perf benefit). 2- Avalonia's ItemsPresenter doesn't support Header and Footer like WinUI does, and so I ignored them. Turns out its kind of needed to fill some gaps, so I've docked the ItemsPresenter in a DockPanel. This shouldn't cause any issues now as this is essentially the same thing as WinUI and TabView doesn't support virtualization right now anyway.

Fix is now in the 2.1 branch

[robloo]

Avalonia for some reason won't render a 1px height Border, so that wasn't even rendering. Rectangle works fine, so these elements were changed to that (which may even be a perf benefit).

Hm, hope I didn't break that. Will keep an eye on it.

[cricketthomas]

Thank you for the fix! Quick question, the border left seems to be different color FA than it is on WinUI but only on dark mode? It's the most unimportant thing but i just noticed it between dark mode and light mode. It almost seems like a WinUi quirk too where the border at the top is slightly lighter than the sides. I am still looking for the resource to style and I can open a PR when I find it (if acceptable or appropriate).

FluentAvaloniaUI 2.1.0-preview2

WinUI

[robloo]

I noticed a darker border in Expander too. I also noticed the CalendarDatePicker symbol icon is now black. Was going to look into this more later but it may be an Avalonia 11.1 issue.