Preserve appearance of collapsed outline headings until window edge

An outline heading does not extend to the right edge of the window when its body is collapsed. This is unfortunate when the used face sets the background color or another property that is visible on whitespace. This package adds overlays to extend the appearance of headings all the way to the right window edge.

(use-package backline
  :after outline
  :config (advice-add 'outline-flag-region :after 'backline-update))

This package should be used together with the outline-minor-faces package. Instead setting the built-in outline-minor-mode-highlight to append also works, but then top-level s-expressions are highlighted as if they were sections, which makes the overview less readable.

Screenshots

Backline and Outline-Minor-Faces

Outline-Minor-Faces only

Neither