scrolling bug; fall-through keys

Wed Jan 11 09:09:19 CET 2012

On Tue, Jan 10, 2012 at 05:04:14PM -0600, Leo Alekseyev wrote:
> I find that evil-previous-line doesn't behave well with
> smooth-scrolling
> (http://www.emacswiki.org/cgi-bin/wiki/SmoothScrolling).  That is, if
> you press "k", when the cursor reaches the top of the window, a new
> page will appear.  It should stop at e.g. 5 lines before window edge
> and smoothly scroll the text.  evil-next-line works as it is supposed
> to, so I suspect this is a bug of some sort.

Fixed in 6b7ff12. Although it's probably a bug in smooth-scrolling as
it does not handle negative prefix arguments for `previous-line' and
`next-line' well (although those are permitted).

> 
> The second issue I've been wondering about is the following: in my
> config, I have 14 lines that make sure that <return> in a particular
> mode does what it was originally bound to, e.g.
> 
>   (evil-declare-key 'motion completion-list-mode-map (kbd "<return>")
> 'choose-completion)
>   (evil-declare-key 'motion completion-list-mode-map "RET" 'choose-completion)
>   (evil-declare-key 'motion browse-kill-ring-mode-map (kbd "<return>")
> 'browse-kill-ring-insert-and-quit)
>   (evil-declare-key 'motion browse-kill-ring-mode-map "RET"
> 'browse-kill-ring-insert-and-quit)
> 
> Is there a better way to make sure that <return> always falls through
> to the current mode's binding, instead of evil-ret?

AFAIK no. The problem is that you have to remove the binding from the
containing keymap, but this is the global evil-motion-state-map in
this case. But I think it is an important issue.

There are several ways to tackle this problem. First one could define
a special symbol (function), say 'evil-undefine, which could be bound
to some key with the effect that it resends the key sequence that
invoked it but with all evil keymaps disabled, e.g., something like
(untested)

(defun evil-undefine ()
  (interactive)
  (let (evil-mode-map-alist)
    (call-interactively (key-binding (this-command-keys)))))

and then    

(evil-declare-key 'motion completion-list-mode-map "RET" 'evil-undefine)

The downside is that C-h k for those keys will return 'evil-undefine
instead of the original key-binding (but one could advise
`key-binding' as well).

A second approach would be to modify `evil-define-key' so that it
automatically inserts the original key-binding, i.e., when enabling
the associated auxiliary keymap all occurences of 'evil-undefine are
replaced (permanently) by the original key-binding. So this variant
would the same as you do in your .emacs file automatically. The
downside of this approach would be that a subsequent modification of
the original keybinding (in the original keymap) would not be
reflected by the auxiliary keymap and thus not be respected.

Perhaps there are other options, we're open for suggestions.

Frank