Eli Zaretskii writes: >> From: Alex >> Date: Wed, 09 Aug 2017 17:29:19 -0600 >> >> Some header-line configurations don't interact nicely with the >> 'highlight' face, particularly when they use the :box attribute. > > Can you elaborate about the problem and why introducing a new face is > the solution for it? > > Thanks. The problem is that the highlight face, which is used for highlighting links and other mouse-sensitive buffer text frequently, may not always look nice with the header-line face. I've attached a picture demonstrating one possible issue. In it, the header-line face has a :box attribute with line-width 4, but the highlight face does not. This results in the characters at the ends being clipped. A new face allows for users to customize it to match the customization of the header-line face while not affecting all other uses of the highlight face. I believe the use case of this face is very similar to 'mode-line-highlight', which was added quite a while ago.