[PATCH] Save and restore point explicitly in `notmuch-wash-toggle-invisible-action'.

[Dmitry Kurochkin]

On Tue, 24 May 2011 16:20:34 -0700, Carl Worth <cworth at cworth.org> wrote:
> On Tue, 24 May 2011 18:43:41 -0400, Austin Clements <amdragon at mit.edu> wrote:
> > Saving point this way is a bit dangerous, though.  For example, if
> > you're near the end of the buffer and shorten the label, attempting to
> > restore the point could result in an error (or, a more benign example:
> > the cursor could wind up outside the label so pressing RET repeatedly
> > won't toggle it).
> > 
> > Unfortunately, I don't know of a clean solution to this, but I think I
> > would rather the cursor move, but stay within the label (probably
> > moving to the beginning), than have problems like the above.
> 
> Here's my fix. Let me know what you think.
> 

(button-end cite-button) would move the point outside the button - to
the next character after it.

Regards,
  Dmitry

> -Carl
> 
> From a32e02bf0d2b57d51695f7d4ea6cdda9acb21322 Mon Sep 17 00:00:00 2001
> From: Carl Worth <cworth at cworth.org>
> Date: Mon, 23 May 2011 19:29:46 +0400
> Subject: [PATCH] Carefully preverse point when changing button text in
>  `notmuch-wash-toggle-invisible-action'.
> 
> Previously, save-excursion was used to attempt to save the point, but
> this was unreliable since the region containing the marker saved by
> save-excursion was deleted. Instead, we save an integer position
> indicating the offset of point within the old button. Then, we restore
> point to the same offset within the new button, (but cap the offset to
> avoid leaving the button entirely).
> ---
>  emacs/notmuch-wash.el |   13 +++++++------
>  1 files changed, 7 insertions(+), 6 deletions(-)
> 
> diff --git a/emacs/notmuch-wash.el b/emacs/notmuch-wash.el
> index 8455eee..3dceb8b 100644
> --- a/emacs/notmuch-wash.el
> +++ b/emacs/notmuch-wash.el
> @@ -82,13 +82,14 @@ collapse the remaining lines into a button.")
>    (let* ((new-start (button-start cite-button))
>  	 (overlay (button-get cite-button 'overlay))
>  	 (button-label (notmuch-wash-button-label overlay))
> +	 (button-offset (- (point) new-start))
>  	 (inhibit-read-only t))
> -    (save-excursion
> -      (goto-char new-start)
> -      (insert button-label)
> -      (let ((old-end (button-end cite-button)))
> -	(move-overlay cite-button new-start (point))
> -	(delete-region (point) old-end))))
> +    (goto-char new-start)
> +    (insert button-label)
> +    (let ((old-end (button-end cite-button)))
> +      (move-overlay cite-button new-start (point))
> +      (delete-region (point) old-end))
> +    (goto-char (min (button-end cite-button) (+ new-start button-offset))))
>    (force-window-update)
>    (redisplay t))
>  
> -- 
> 1.7.5.1
> 
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