So far I'm satisfied with this feature because it implements the
intuitive and natural behavior expected from the modern tab bar.

As for details of the implementation, it currently depends on the
availability of the external program `convert' used to render the tab
bar elements.  I hope it could be replaced with a separate bar similar
to the tool-bar.  I think we should do this as soon as possible because
this single feature can improve Emacs usability for most users that expect
a tab bar is a standard editor feature.