Re: Control help- and Info-mode buffers from other buffers

[Juri Linkov <juri@linkov.net>]

> Anyway, pre/post hook hack is very useful, and works with many commands, but not
> with all, so it is not 100% failsafe and general.Try to execute Info-mode
> from other window but Info (shortcut 'm'). In my Emacs it does not work.

I tried 'm' (Info-menu), and it works nicely without any problem.
As long as key prefixes are the same in both windows.

> Another problem with the above is that this will work only for 'other-window'
> for which Emacs has an algorithm to figure out which window it is. But what when
> you have more then two windows, and wish to switch to a different window than
> what Emacs considers as 'other-window'? You will have to prompt the user, to
> choose one. The help or info buffers are seldom the 'other-buffer' so constanly
> choosing the window would be just as annoying as constantly switching to and
> from, in my opinion.

Indeed, which window to use is a separate question.

For the existing commands scroll-other-window, scroll-other-window-down,
recenter-other-window, beginning-of-buffer-other-window,
end-of-buffer-other-window, the user option that defines which window to use
is 'other-window-scroll-default', and it can be customized
to any function, for example, a function that looks for
a window with a Help/Info buffer on the current frame,
or on any other frame.  Or to a function that uses
'get-mru-window' to get the most recently used/displayed window.
All this is customizable.

> I would prefer if there was a code gen in form of a macro, as suggested, similar
> to define-minor-mode, that does this switching on pre-defined prefixes so that
> we get uniformity, and helps people write commands so they work from
> anywhere. Since it is not possible to completely automate it, perhaps lisp
> manual could mention how to write commands so they are callable from other
> windows then just selected one.

The downside is that every command needs to be modified and its body
wrapped with a macro.  An alternative would be to put a new property
on the command symbol with a function that selects a window to redirect
input to.  Implementation-wise this is like repeat-mode works.
Additionally, this will allow making redirected keys repeatable
like Manuel asked to do.  Then:

Currently:
  C-x o SPC SPC SPC DEL C-x o

With a prefix before every key:
  C-h M-i SPC C-h M-i SPC C-h M-i SPC C-h M-i DEL
or with a shorter prefix key:
  M-i SPC M-i SPC M-i SPC M-i DEL

With repeatable key sequences:
  C-h M-i SPC SPC SPC DEL + some key to terminate the sequence
                            of redirecting input to another window

> I don't say you should not include the pre/post hack into Emacs if you want, it
> is better then what already is there for the similar purpose (don't remember
> longer the one included since I don't use it). I am just saying that we should
> perhaps write better commands in the future, so we don't need the hack :).

And I don't say that the pre/post approach is more reliable.
There are other alternatives for general code to select a window
before executing a command as opposed to modifying every command.