Proposal: allow ProgressBar's background to be customable when Indeterminate=true

[aries-zhang]

Proposal: allow ProgressBar's background to be customable when Indeterminate=true

Summary

According to code here: https://github.com/microsoft/microsoft-ui-xaml/blob/589ced40542b9b4de2fddf0e58a1e3eecd164e2f/src/controls/dev/ProgressBar/ProgressBar.xaml#L98C1-L99C1, ProgressBar control's track is hidden when it's in Indeterminate mode, which makes Background property invalid.

It would make more sense if users were allowed to set whether the background track is visible in both modes.

Rationale

• Background property becomes invalid in Indeterminate mode, and there is no way to find this unless referring to the XAML code.
• It is unnecessarily harder to customize the ProgressBar control when UI designs have a visible background track.

Scope

Important Notes

Open Questions

[JohnnyWestlake]

Technically it is already fully customisable - it is the design goal of XAML controls using control templates. The supported way to do this would be to retemplate/copy the template and do whatever you want with it.