bug#33870: 27.0.50; xref-goto-xref not configurable

[Juri Linkov]

>>> Also I'm not complaining that flymake steals the fringe indicator from
>>> diff-hl-mode, although there is no conflict because diff-hl-mode
>>> uses the background color whereas flymake uses the foreground color,
>>> so they can peacefully coexist together on the fringe.
>>
>> If only fringes supported that kind of merging. BTW, diff-hl-mode uses the
>> foreground color for the border, but any kind of merging would be
>> an improvement.
>
> I thought that since add-face-text-property supports face merging
> maybe it would be possible to do the same with fringes,
> but I have not investigated how feasible it is.

Also the question which one to call on clicking the fringe indicator?
It seems for flymake there is no reasonable action to call on click, so
diff-hl-mode is free to use mouse clicks to show the corresponding diff.