bug#56896: 29.0.50; [PATCHv3] Make the bookmark fringe icon look like a bookmark

[Lars Ingebrigtsen <larsi@gnus.org>]

Jim Porter <jporterbugs@gmail.com> writes:

> Here's a better version of this patch. Rather than a proxy object, it
> just sets the 'fringe' property on the defcustom, which the rest of
> the bookmark code can then use like a "regular" fringe bitmap
> (essentially, it's just an alias to a real fringe bitmap). I also
> added a 'fringe-custom-set-bitmap' function that anyone can use as a
> :set function.

Makes sense to me; please go ahead and push.

> This should be general enough that it could be used wherever anyone
> wants to allow users to use Customize to change the fringe bitmap that
> gets used for a particular purpose. Potentially, it could even be used
> for *every* use of a fringe bitmap. That would let users pick icons
> they like for a particular purpose based on their general description
> (e.g. 'right-triangle'), but they could also independently adjust the
> bitmaps (e.g. redefining all the fringe bitmaps to be larger for high
> DPI monitors). For the latter case, maybe users could download a
> package from ELPA to do that.

I wonder whether we could usefully fold this stuff into the new icons.el
library.  I'm not sure how, though, because the fringe stuff is so low
level.  And icons.el is all about graceful degradation, and there's not
much to degrade to in a fringe context.