emacs page up page down

<a href="http://gnu.org/software/emacs/"><img src="gnu.jpg"></a>
<a href="emacs_page_up_page_down"><img src="page_up_key.jpg"></a>
<a href="emacs_page_up_page_down"><img src="page_down_key.jpg"></a>

By
default, the page up and page down keys in
[Emacs](http://gnu.org/software/emacs/) move the _screen_ up and down, not the
point. As a result, if the screen is already at the bottom of the buffer, page
down does nothing.

I don't know about you, but this annoys me. Even if the screen is at the bottom
of the buffer, I want page down to move the _point_ to the bottom of the buffer
if it's not already there. So, I set out to make page up and page down move the
point up and down a page. The screen should also scroll to follow it, if
necessary, but that should be a side effect.

I first looked at [pager.el](http://user.it.uu.se/~mic/pager.el). It's close -
it moves the point, not the screen - but it still errors if the screen is
already at the end of the buffer.

I next looked at
[pc-selection-mode](http://www.gnu.org/software/emacs/manual/html_node/Emulation.html),
which comes with Emacs (in pc-mode.el). It binds page down and page up to
`scroll-down-nomark` and `scroll-up-nomark`, which do what I want, but they also
disable the mark. Argh!

So, I stole the code and hacked it to leave the mark alone. I ended up with this
elisp, which makes page up and page down behave exactly the way I want:

    ;; Page down/up move the point, not the screen.
    ;; In practice, this means that they can move the
    ;; point to the beginning or end of the buffer.
    (global-set-key [next]
      (lambda () (interactive)
        (condition-case nil (scroll-up)
          (end-of-buffer (goto-char (point-max))))))

    (global-set-key [prior]
      (lambda () (interactive)
        (condition-case nil (scroll-down)
          (beginning-of-buffer (goto-char (point-min))))))