GNU bug report logs - #102
keymap property ignored for mouse click on overlay

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Message #22 received at 102 <at> emacsbugs.donarmstrong.com (full text, mbox):

From: Chong Yidong <cyd <at> stupidchicken.com>
To: "Drew Adams" <drew.adams <at> oracle.com>
Cc: "'Martin Rudalics'" <rudalics <at> gmx.at>, <102 <at> debbugs.gnu.org>
Subject: Re: keymap property ignored for mouse click on overlay
Date: Wed, 16 Apr 2008 13:48:12 -0400

"Drew Adams" <drew.adams <at> oracle.com> writes:

>> The following patch implements the behavior you are looking for:
>> mouse clicks on before/after strings and display strings will use the
>> `keymap' overlay or text property associated with the text
>> position---unless the string itself defines a `keymap' text property,
>> in which case that keymap is used instead.
>> 
>> Could you test it out?  Please test as many combinations of
>> keymaps/overlays/textprops as possible.  Test the output of 
>> C-h k also.
>
> I can't build Emacs, sorry. If it were Lisp only, I would test it.

After studying this some more, I've decided to leave the current
behavior alone.

It turns out that the patch I posted earlier doesn't work for
after-strings, because the buffer position associated with an
after-string is the end of the overlay (1 + the postition of the last
character).  As a result, there's no efficient way for read_key_sequence
to detect the existence of an overlay with a keymap for an after-string.

The fact that the buffer position of an after-string is the overlay end
isn't easily changed, because the redisplay engine relies on this for
efficiency (it means that the redisplay iterator can process all the
strings at a given charpos, before processing the buffer text).

Since the benefit of this feature is rather marginal in the first place,
I think it's better to simply document that display strings don't
inherit keymaps.  The way to DTRT is to give the display string a
'keymap text property, which has always worked.

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