bug#13523: 24.2.92; [regression] mark-active

[Leo Liu]

I have just wasted a few hours wondering some odd behaviour in js2-mode
but to discover it is due to change between Emacs 23 and 24.

1. (global-set-key [mouse-1] (lambda (e) (interactive "e")))
2. Mouse-1 click on a buffer and check the value of mark-active

In emacs 23 it is nil; but in emacs 24.2/24.2.92, it is t.

With mark-active set to t, some commands following mouse-1 activate the
region unexpectedly and inconveniently, for example, in js2-mode, C-a
activate the region between the mouse and line beginning.

It seems 23 and 24 is consistent only if [mouse-1] is bound to
mouse-set-point.

As a result of this bug, most customised [mouse-1] commands fail to
handle mark-active i.e. it is subtle and hard to get the customised
mouse-1 command behave like mouse-set-point leaving users with creepy
behaviour like the one I am seeing in js2 mode.

Leo