bug#20398: 25.0.50; Clicking `window-divider-last-pixel' in help for `window-divider'

[martin rudalics]

> widget-documentation-link-action is surprisingly simplistic.

I tried to make following links less simplistic in 557c7d6..62fe329 on
master.

> It doesn't even know that faces exist.
> It should do what `help-make-xrefs' does, and use the presence of "face"
> etc in the doc string as a cue. Ideally it would reuse the same code.

Ideally, yes.  Currently, I'm troubled by


Debugger entered--Lisp error: (error "No selection is available")
  signal(error ("No selection is available"))
  error("No selection is available")
  gui-get-primary-selection()
  mouse-yank-primary((mouse-2 (#<window 3 on *Customize Face: window-divider*> 
615 (355 . 257) 4390875 nil 615 (42 . 14) nil (3 . 7) (8 . 16))))
  funcall-interactively(mouse-yank-primary (mouse-2 (#<window 3 on *Customize 
Face: window-divider*> 615 (355 . 257) 4390875 nil 615 (42 . 14) nil (3 . 7) (8 . 
16))))
  call-interactively(mouse-yank-primary nil nil)
  command-execute(mouse-yank-primary)


with <mouse-1> on any such link in a customization buffer.  Can anyone
see this?  Does anyone have an idea where this mouse-2 yanking attempt
comes from?

martin