Re: hideshow condensed view

[Thien-Thi Nguyen]

() Andreas Roehler <andreas.roehler@online.de>
() Thu, 25 Feb 2010 15:24:24 +0100

   thanks a lot maintaining hideshow.el.

In the last few years, i can't take any credit for its improvement.
See Emacs' ChangeLog for those who actually merit the appreciation...

   Use it as default outline-mode now.

Cool.

   Just one thing remains so far: hs displays an empty
   line between headers. Would prefer a more condensed
   view.

You must have good eyes (still); i use hideshow not
for density but for spaciousness.

   Might it be possible to introduce a function
   `hide-all-empty-lines', inclusive a variable which may
   be customized?

Yeah, it would be possible, but i tend to think of empty lines outside
the (top-level) blocks as also outside the scope of hideshow.  It's like
in the book GEB, there is the tree and there is the stuff outside the
tree.  Get it?

I am already troubled by hideshow straying from its conceptual (both
meanings) simplicity -- a block is between matching parens, no more no
less -- but that's just me...

All this is to say, you probably should write a "squash minor mode",
which puts the invisible property on an overlay for text that matches
the empty line regexp (which of course, could be made customizable), at
which point my advice would be to add a hook to `hs-hide-all' to enable
this mode.

Here's a quick (but tested (lightly)) sketch:

 (defvar empty-lines-rx "^\\s-*\\(\n\\s-*\\)+")
 
 (defvar empty-lines nil
   "List of empty lines (overlays).")
 
 (defvar squash-minor-mode nil)
 
 (defun squash-minor-mode () 
   (interactive)
   (setq squash-minor-mode (not squash-minor-mode))
   (if squash-minor-mode
       (save-excursion
         (goto-char (point-min))
         (while (re-search-forward empty-lines-rx nil t)
           (let ((ov (make-overlay (match-beginning 0) (match-end 0))))
             (overlay-put ov 'display "")
             (push ov empty-lines))))
     (mapc 'delete-overlay empty-lines)
     (setq empty-lines nil))
   (message "empty-lines squashing %s" (if squash-minor-mode 'on 'off)))
 
Have fun!

thi