bug#15312: Info (point-entered, point-left): Doc incomplete, hence incorrect

[Stefan Monnier]

> Perhaps we need to step back and talk about the situations where these
> hooks are supposed to be used.  Because I cannot see any sense in
> calling the hooks when the values of these properties don't change.

Agreed, but the code also runs the hook when the value of the
`point-entered' does not change but the value of some unrelated
property changes.  That is an error.

>> The right thing to do is to declare point-entered and point-left
>> properties as obsolete and replace them by something like cursor-entered
>> and cursor-left properties which are only checked at command boundaries
>> (or better, checked just before redisplay).
> Redisplay can be forced as part of a command.

I know, and I think that for most uses of these kinds of properties we'd
also want to run the hook when redisplay is called in the middle of
a command (e.g. in the middle of query-replace).  Note that we'd probably
also want to run the hook when redisplay is short-circuited by pending input.


        Stefan