RE: generate 3) S-mouse-2: follow link in new window

["Drew Adams" <drew.adams@oracle.com>]

>     "Bearable" and getting "bitten on a somewhat regular basis" hardly
>     constitute a ringing endorsement. I wouldn't buy an insect
>     repellent based on that testimonial. ;-)
>
> This feature was set up as it is to provide compatibility with many
> other graphical interfaces.  We expected this to be good for
> beginners.  If helps beginners start using Emacs, it is worth keeping.
> Experienced people can customize it.
>
> Whether it really achieves that goal, I don't know.  It would be nice
> to get some real data about that, but that is not a trivial task.

Here's a thought -

Have `ask' be the default value of `mouse-1-click-follows-link', and have a
behavior similar to that of `disable-command':

If the value is `ask', then the first time (only) that a user clicks a link
with `mouse-1', s?he is asked this:

 "You have clicked a link using `mouse-1'. In Emacs, clicking
 `mouse-2' follows links, and `mouse-1' has other uses.
 Do you also want clicking `mouse-1' to follow links?"

If the answer is "yes", then the value is changed to 450 (the current
default value). Otherwise, it is changed to nil. The new value is saved
(Customize). A message echoes the new value and the option name, for future
reference.

This behavior has these advantages:

* It tells the user which button `mouse-1' is ("You have clicked...").

* It makes the user aware of what the choices are and what the variable is
that governs them.

* It requires an explicit user choice. It does so at the right time: first
link click.

* It states that `mouse-2' is standard for following links and it will
continue to follow links in any case. It does not explicitly refer to any
disadvantages for `mouse-1' following links, but `mouse-2' as the "standard"
might lead some new users to give it a try. Many new users are open to
learning the Emacs way.

* It has zero impact on anyone who has already customized the option. It has
negligeable impact on anyone who has not - a user need answer the question
at most once.

WDOT?