Tabbar Toolbar Update Behavior Inconsistent

[colin-grant-work]

Bug Description:

Tabbar items can be registered with an onDidChange event that causes tabbars to be rerendered. This is successfully carried through in the main toolbars each view area, but toolbars in ViewContainer parts do not update when a change event is fired.

Steps to Reproduce:

1. Register a toolbar item that includes a didChange event and should appear in a ViewContainer part (for example, one that is attached to part of the debug panel or one that is attached to the file explorer when a plugin contribution (e.g. NPM) is also present).
2. Hover to reveal the toolbar and fire the command to trigger the didChange event.
3. Observe that the event does not affect the ViewContainer part toolbar.

Additional Information

Observe that the main view toolbar updates, but the ViewContainer part toolbar only updates when it is hidden and then shown again.

• Operating System: RHEL
• Theia Version: master

[colin-grant-work]

Actually the problem is deeper than I realized, because setting up a ViewContainer's tabbar is handled by ViewContainer.updateTitle but, if it's docked in a side panel, updating for a change event is handled by SidePanelToolbar.updateToolbar and the two give different results, because the ViewContainer knows to look at its own parts, but the SidePanelToolbar is ignorant of the details of the widget occupying the space, so you actually have quite different code getting run.

[colin-grant-work]

I think that I will let the PR I made (#8967) stand as the fix for the bug described here, and file a separate issue for the weird behavior more generally.

[colin-grant-work]

This has been addressed by subsequent work on tabbar toolbar items.