Re: use of `mouse-face' to delimit text zones [was: bidi-display-reordering is now non-nil by default]

[Stefan Monnier]

> That's it.  Not a word about potential use of that for doing anything
> else besides displaying the text.

Nothing prevents packages from (ab)using it for various other things at
the same time, of course.

> How is Joe R. Hacker supposed to know that adding invisible characters
> to a portion of text covered by mouse-face will break completion??

We're talking about a property added *by the completion code* and *for
the completion code*.  I.e. an internal use.  Joe R. Hacker doesn't need
to know about it unless he actually hacks on the code that handles
minibuffer-completion-help.

> Btw, mouse-face can also be put on overlay strings and display
> strings; how can you get the underlying text then?

Again, it's an internal use: the completion code doesn't use overlay
strings and doesn't care about display strings: it puts the mouse-face
property where it needs it and nowhere else.  It's been that way
probably ever since the *Completions* code was enhanced with mouse-face
highlighting (not sure what it used before).

Anyway, this is all irrelevant to this thread (I was just pointing out
the need for a trivial tweak to your patch if we intend to use it).


        Stefan