bug#4896: DocView: Continuous mode

[Juri Linkov <juri@jurta.org>]

> > I think mouse-4/5 once where bound to
> > doc-view-scroll-down-or-previous-page and
> > doc-view-scroll-down-or-previous-page previously, so they scrolled or
> > switched pages back then.  I don't know why this was changed.  I guess,
> > because one "press" of mouse-4/5 scrolled a half page, which was a bit
> > unusual...
>
> I can't remember why it was changed either, but I for one would dislike
> it if scrolling the image with the wheel would suddenly switch to the
> next/previous page: when I scroll it's usually because I want to center
> the image differently.
>
> So I do think that we need 2 modes: a continuous mode and the current mode.

The following patch adds a new variable `doc-view-continuous-mode'
and uses it in two new commands `doc-view-next-line-or-next-page'
and `doc-view-previous-line-or-previous-page'.  However, I still
have no idea how make the mouse-wheel to jump to the next/previous
page depending on the value of `doc-view-continuous-mode'.

Index: lisp/doc-view.el
===================================================================
RCS file: /sources/emacs/emacs/lisp/doc-view.el,v
retrieving revision 1.88
diff -c -r1.88 doc-view.el
*** lisp/doc-view.el	17 Jul 2009 19:43:53 -0000	1.88
--- lisp/doc-view.el	23 Nov 2009 09:45:37 -0000
***************
*** 222,227 ****
--- 222,236 ----
    :type 'integer
    :group 'doc-view)
  
+ (defcustom doc-view-continuous-mode nil
+   "In Continuous mode reaching the page edge advances to the next/previous page.
+ When non-nil, scrolling a line upward at the bottom edge of the page
+ moves to the next page, and scrolling a line downward at the top edge
+ of the page moves to the previous page."
+   :type 'boolean
+   :group 'doc-view
+   :version "23.2")
+ 
  ;;;; Internal Variables
  
  (defun doc-view-new-window-function (winprops)
***************
*** 286,291 ****
--- 295,304 ----
      (define-key map [remap backward-page] 'doc-view-previous-page)
      (define-key map (kbd "SPC")       'doc-view-scroll-up-or-next-page)
      (define-key map (kbd "DEL")       'doc-view-scroll-down-or-previous-page)
+     (define-key map (kbd "C-n")       'doc-view-next-line-or-next-page)
+     (define-key map (kbd "<down>")    'doc-view-next-line-or-next-page)
+     (define-key map (kbd "C-p")       'doc-view-previous-line-or-previous-page)
+     (define-key map (kbd "<up>")      'doc-view-previous-line-or-previous-page)
      (define-key map (kbd "M-<")       'doc-view-first-page)
      (define-key map (kbd "M->")       'doc-view-last-page)
      (define-key map [remap goto-line] 'doc-view-goto-page)
***************
*** 442,447 ****
--- 455,492 ----
  	(image-bol 1))
        (set-window-hscroll (selected-window) hscroll))))
  
+ (defun doc-view-next-line-or-next-page (&optional n)
+   "Scroll upward by N lines if possible, else goto next page.
+ When `doc-view-continuous-mode' is non-nil, scrolling a line upward at
+ the bottom edge of the page moves to the next page."
+   (interactive "p")
+   (if doc-view-continuous-mode
+       (let ((hscroll (window-hscroll))
+ 	    (cur-page (doc-view-current-page)))
+ 	(when (= (window-vscroll) (image-next-line n))
+ 	  (doc-view-next-page)
+ 	  (when (/= cur-page (doc-view-current-page))
+ 	    (image-bob)
+ 	    (image-bol 1))
+ 	  (set-window-hscroll (selected-window) hscroll)))
+     (image-next-line 1)))
+ 
+ (defun doc-view-previous-line-or-previous-page (&optional n)
+   "Scroll downward by N lines if possible, else goto previous page.
+ When `doc-view-continuous-mode' is non-nil, scrolling a line downward
+ at the top edge of the page moves to the previous page."
+   (interactive "p")
+   (if doc-view-continuous-mode
+       (let ((hscroll (window-hscroll))
+ 	    (cur-page (doc-view-current-page)))
+ 	(when (= (window-vscroll) (image-previous-line n))
+ 	  (doc-view-previous-page)
+ 	  (when (/= cur-page (doc-view-current-page))
+ 	    (image-eob)
+ 	    (image-bol 1))
+ 	  (set-window-hscroll (selected-window) hscroll)))
+     (image-previous-line n)))
+ 
  ;;;; Utility Functions
  
  (defun doc-view-kill-proc ()

-- 
Juri Linkov
http://www.jurta.org/emacs/