Copyright (C) 2001-2022 Free Software Foundation, Inc. See the end of the file for license conditions.

This is a feature branch for adding continuous scroll to Emacs doc-view (and pdf-tools).

The code in the doc-view package (and even more pdf-tools) is not trivial. In order to understand the code, we keep notes here where we describe or map out the working mechanism behind the package.

Here is an edebug trace for opening a document (that has already been fully converted), where we have left out the calls to some none essential functions (divided over two example blocks so that we can fold them separately):

{ doc-view-mode args: nil
:{ doc-view-set-up-single-converter args: nil
:} doc-view-set-up-single-converter result: page-%s.png
:{ doc-view-make-safe-dir args: (/tmp/docview1000)
:} doc-view-make-safe-dir result: nil
:{ image-mode-setup-winprops args: nil
:} image-mode-setup-winprops result: (image-mode-reapply-winprops t)
:{ doc-view-initiate-display args: nil
::{ doc-view-buffer-message args: nil
:::{ image-mode-window-get args: (overlay nil)
::::{ image-mode-winprops args: (nil nil)
:::::{ doc-view-new-window-function args: ((t))
::::::{ image-mode-window-get args: (overlay (t))
::::::} image-mode-window-get result: nil
::::::{ image-mode-window-put args: (overlay #<overlay in no buffer> (t))
::::::} image-mode-window-put result: ((overlay . #<overlay in no buffer>))
:::::} doc-view-new-window-function result: nil
::::} image-mode-winprops result: (t (overlay . #<overlay in no buffer>))
:::} image-mode-window-get result: #<overlay in no buffer>
:::{ image-mode-window-get args: (overlay nil)
::::{ image-mode-winprops args: (nil nil)
::::} image-mode-winprops result: (t (overlay . #<overlay in no buffer>))
:::} image-mode-window-get result: #<overlay in no buffer>
::} doc-view-buffer-message result: Welcome to DocView!

If you see this buffer it means that ....

@@html:<details><summary>show trace remainder</summary>@@

::{ image-mode-window-get args: (page nil)
:::{ image-mode-winprops args: (nil nil)
:::} image-mode-winprops result: (t (overlay . #<overlay in no buffer>))
::} image-mode-window-get result: nil
::{ image-mode-window-put args: (page 1 nil)
:::{ image-mode-winprops args: (nil nil)
:::} image-mode-winprops result: (t (overlay . #<overlay in no buffer>))
::} image-mode-window-put result: ((page . 1) (overlay . #<overlay in no buffer>))
::{ doc-view-already-converted-p args: nil
:::{ doc-view--current-cache-dir args: nil
::::{ doc-view-make-safe-dir args: (/tmp/docview1000)
::::} doc-view-make-safe-dir result: nil
:::} doc-view--current-cache-dir result: /tmp/docview1000/GNU Emacs Lisp Reference Manual_ For Emacs - Bil Lewis.pdf-dce847ffdfa273bf0fc346f8c3c5927a/
:::{ doc-view--current-cache-dir args: nil
:::} doc-view--current-cache-dir result: /tmp/docview1000/GNU Emacs Lisp Reference Manual_ For Emacs - Bil Lewis.pdf-dce847ffdfa273bf0fc346f8c3c5927a/
:::{ doc-view--current-cache-dir args: nil
:::} doc-view--current-cache-dir result: /tmp/docview1000/GNU Emacs Lisp Reference Manual_ For Emacs - Bil Lewis.pdf-dce847ffdfa273bf0fc346f8c3c5927a/
::} doc-view-already-converted-p result: t
::{ doc-view--current-cache-dir args: nil
::} doc-view--current-cache-dir result: /tmp/docview1000/GNU Emacs Lisp Reference Manual_ For Emacs - Bil Lewis.pdf-dce847ffdfa273bf0fc346f8c3c5927a/
::{ doc-view-display args: (GNU Emacs Lisp Reference Manual_ For Emacs - Bil Lewis.pdf force)
:::{ doc-view--current-cache-dir args: nil
:::} doc-view--current-cache-dir result: /tmp/docview1000/GNU Emacs Lisp Reference Manual_ For Emacs - Bil Lewis.pdf-dce847ffdfa273bf0fc346f8c3c5927a/
:::{ image-mode-window-get args: (page t)
::::{ image-mode-winprops args: (t nil)
::::} image-mode-winprops result: (t (page . 1) (overlay . #<overlay in no buffer>))
:::} image-mode-window-get result: 1
:::{ doc-view--current-cache-dir args: nil
:::} doc-view--current-cache-dir result: /tmp/docview1000/GNU Emacs Lisp Reference Manual_ For Emacs - Bil Lewis.pdf-dce847ffdfa273bf0fc346f8c3c5927a/
:::{ doc-view-goto-page args: (1)
::::{ doc-view-last-page-number args: nil
::::} doc-view-last-page-number result: 1337
::::{ image-mode-window-put args: (page 1 nil)
:::::{ image-mode-winprops args: (nil nil)
:::::} image-mode-winprops result: (t (page . 1) (overlay . #<overlay in no buffer>))
::::} image-mode-window-put result: ((page . 1) (overlay . #<overlay in no buffer>))
::::{ image-mode-window-put args: (info Page 1 of 1337.
 nil)
:::::{ image-mode-winprops args: (nil nil)
:::::} image-mode-winprops result: (t (page . 1) (overlay . #<overlay in no buffer>))
::::} image-mode-window-put result: ((info . Page 1 of 1337.
) (page . 1) (overlay . #<overlay in no buffer>))
::::{ doc-view--current-cache-dir args: nil
::::} doc-view--current-cache-dir result: /tmp/docview1000/GNU Emacs Lisp Reference Manual_ For Emacs - Bil Lewis.pdf-dce847ffdfa273bf0fc346f8c3c5927a/
::::{ doc-view-insert-image args: (/tmp/docview1000/GNU Emacs Lisp Reference Manual_ For Emacs - Bil Lewis.pdf-dce847ffdfa273bf0fc346f8c3c5927a/page-1.png (:pointer arrow))
:::::{ image-mode-window-get args: (overlay nil)
::::::{ image-mode-winprops args: (nil nil)
::::::} image-mode-winprops result: (t (info . Page 1 of 1337.
) (page . 1) (overlay . #<overlay in no buffer>))
:::::} image-mode-window-get result: #<overlay in no buffer>
::::} doc-view-insert-image result: nil
::::{ image-mode-window-get args: (overlay nil)
:::::{ image-mode-winprops args: (nil nil)
:::::} image-mode-winprops result: (t (info . Page 1 of 1337.
) (page . 1) (overlay . #<overlay in no buffer>))
::::} image-mode-window-get result: #<overlay in no buffer>
::::{ image-mode-window-get args: (info nil)
:::::{ image-mode-winprops args: (nil nil)
:::::} image-mode-winprops result: (t (info . Page 1 of 1337.
) (page . 1) (overlay . #<overlay in no buffer>))
::::} image-mode-window-get result: Page 1 of 1337.

:::} doc-view-goto-page result: Page 1 of 1337.

::} doc-view-display result: nil
:} doc-view-initiate-display result: Type C-c C-c to toggle between editing or viewing the document.
} doc-view-mode result: nil
{ image-mode-reapply-winprops args: nil
:{ image-mode-winprops args: (nil t)
::{ edebug-anon1613 args: ((t (info . Page 1 of 1337.
) (page . 1) (overlay . #<overlay in no buffer>)))
::} edebug-anon1613 result: (t (info . Page 1 of 1337.
) (page . 1) (overlay . #<overlay in no buffer>))
::{ doc-view-new-window-function args: ((#<window 3 on GNU Emacs Lisp Reference Manual_ For Emacs - Bil Lewis.pdf> (info . Page 1 of 1337.
) (page . 1) (overlay . #<overlay in no buffer>)))
:::{ image-mode-window-get args: (overlay (#<window 3 on GNU Emacs Lisp Reference Manual_ For Emacs - Bil Lewis.pdf> (info . Page 1 of 1337.
) (page . 1) (overlay . #<overlay in no buffer>)))
:::} image-mode-window-get result: #<overlay in no buffer>
:::{ image-mode-window-put args: (overlay #<overlay from 1 to 7030463 in GNU Emacs Lisp Reference Manual_ For Emacs - Bil Lewis.pdf> (#<window 3 on GNU Emacs Lisp Reference Manual_ For Emacs - Bil Lewis.pdf> (info . Page 1 of 1337.
) (page . 1) (overlay . #<overlay in no buffer>)))
::::{ image-mode-window-put args: (overlay #<overlay from 1 to 7030463 in GNU Emacs Lisp Reference Manual_ For Emacs - Bil Lewis.pdf> t)
:::::{ image-mode-winprops args: (t nil)
:::::} image-mode-winprops result: (t (info . Page 1 of 1337.
) (page . 1) (overlay . #<overlay in no buffer>))
::::} image-mode-window-put result: ((overlay . #<overlay from 1 to 7030463 in GNU Emacs Lisp Reference Manual_ For Emacs - Bil Lewis.pdf>) (info . Page 1 of 1337.
) (page . 1))
:::} image-mode-window-put result: ((overlay . #<overlay from 1 to 7030463 in GNU Emacs Lisp Reference Manual_ For Emacs - Bil Lewis.pdf>) (info . Page 1 of 1337.
) (page . 1))
:::{ image-mode-window-get args: (page t)
::::{ image-mode-winprops args: (t nil)
::::} image-mode-winprops result: (t (overlay . #<overlay from 1 to 7030463 in GNU Emacs Lisp Reference Manual_ For Emacs - Bil Lewis.pdf>) (info . Page 1 of 1337.
) (page . 1))
:::} image-mode-window-get result: 1
:::{ doc-view-goto-page args: (1)
::::{ doc-view-last-page-number args: nil
::::} doc-view-last-page-number result: 1337
::::{ image-mode-window-put args: (page 1 nil)
:::::{ image-mode-winprops args: (nil nil)
:::::} image-mode-winprops result: (#<window 3 on GNU Emacs Lisp Reference Manual_ For Emacs - Bil Lewis.pdf> (overlay . #<overlay from 1 to 7030463 in GNU Emacs Lisp Reference Manual_ For Emacs - Bil Lewis.pdf>) (info . Page 1 of 1337.
) (page . 1))
:::::{ image-mode-window-put args: (page 1 t)
::::::{ image-mode-winprops args: (t nil)
::::::} image-mode-winprops result: (t (overlay . #<overlay from 1 to 7030463 in GNU Emacs Lisp Reference Manual_ For Emacs - Bil Lewis.pdf>) (info . Page 1 of 1337.
) (page . 1))
:::::} image-mode-window-put result: ((page . 1) (overlay . #<overlay from 1 to 7030463 in GNU Emacs Lisp Reference Manual_ For Emacs - Bil Lewis.pdf>) (info . Page 1 of 1337.
))
::::} image-mode-window-put result: ((page . 1) (overlay . #<overlay from 1 to 7030463 in GNU Emacs Lisp Reference Manual_ For Emacs - Bil Lewis.pdf>) (info . Page 1 of 1337.
))
::::{ image-mode-window-put args: (info Page 1 of 1337.
 nil)
:::::{ image-mode-winprops args: (nil nil)
:::::} image-mode-winprops result: (#<window 3 on GNU Emacs Lisp Reference Manual_ For Emacs - Bil Lewis.pdf> (page . 1) (overlay . #<overlay from 1 to 7030463 in GNU Emacs Lisp Reference Manual_ For Emacs - Bil Lewis.pdf>) (info . Page 1 of 1337.
))
:::::{ image-mode-window-put args: (info Page 1 of 1337.
 t)
::::::{ image-mode-winprops args: (t nil)
::::::} image-mode-winprops result: (t (page . 1) (overlay . #<overlay from 1 to 7030463 in GNU Emacs Lisp Reference Manual_ For Emacs - Bil Lewis.pdf>) (info . Page 1 of 1337.
))
:::::} image-mode-window-put result: ((info . Page 1 of 1337.
) (page . 1) (overlay . #<overlay from 1 to 7030463 in GNU Emacs Lisp Reference Manual_ For Emacs - Bil Lewis.pdf>))
::::} image-mode-window-put result: ((info . Page 1 of 1337.
) (page . 1) (overlay . #<overlay from 1 to 7030463 in GNU Emacs Lisp Reference Manual_ For Emacs - Bil Lewis.pdf>))
::::{ doc-view--current-cache-dir args: nil
::::} doc-view--current-cache-dir result: /tmp/docview1000/GNU Emacs Lisp Reference Manual_ For Emacs - Bil Lewis.pdf-dce847ffdfa273bf0fc346f8c3c5927a/
::::{ doc-view-insert-image args: (/tmp/docview1000/GNU Emacs Lisp Reference Manual_ For Emacs - Bil Lewis.pdf-dce847ffdfa273bf0fc346f8c3c5927a/page-1.png (:pointer arrow))
:::::{ image-mode-window-get args: (overlay nil)
::::::{ image-mode-winprops args: (nil nil)
::::::} image-mode-winprops result: (#<window 3 on GNU Emacs Lisp Reference Manual_ For Emacs - Bil Lewis.pdf> (info . Page 1 of 1337.
) (page . 1) (overlay . #<overlay from 1 to 7030463 in GNU Emacs Lisp Reference Manual_ For Emacs - Bil Lewis.pdf>))
:::::} image-mode-window-get result: #<overlay from 1 to 7030463 in GNU Emacs Lisp Reference Manual_ For Emacs - Bil Lewis.pdf>
:::::{ image-mode-window-get args: (slice nil)
::::::{ image-mode-winprops args: (nil nil)
::::::} image-mode-winprops result: (#<window 3 on GNU Emacs Lisp Reference Manual_ For Emacs - Bil Lewis.pdf> (info . Page 1 of 1337.
) (page . 1) (overlay . #<overlay from 1 to 7030463 in GNU Emacs Lisp Reference Manual_ For Emacs - Bil Lewis.pdf>))
:::::} image-mode-window-get result: nil
:::::{ image-mode-window-put args: (image (image :type png :file /tmp/docview1000/GNU Emacs Lisp Reference Manual_ For Emacs - Bil Lewis.pdf-dce847ffdfa273bf0fc346f8c3c5927a/page-1.png :scale 1 :pointer arrow :width 850 :transform-smoothing t) nil)
::::::{ image-mode-winprops args: (nil nil)
::::::} image-mode-winprops result: (#<window 3 on GNU Emacs Lisp Reference Manual_ For Emacs - Bil Lewis.pdf> (info . Page 1 of 1337.
) (page . 1) (overlay . #<overlay from 1 to 7030463 in GNU Emacs Lisp Reference Manual_ For Emacs - Bil Lewis.pdf>))
::::::{ image-mode-window-put args: (image (image :type png :file /tmp/docview1000/GNU Emacs Lisp Reference Manual_ For Emacs - Bil Lewis.pdf-dce847ffdfa273bf0fc346f8c3c5927a/page-1.png :scale 1 :pointer arrow :width 850 :transform-smoothing t) t)
:::::::{ image-mode-winprops args: (t nil)
:::::::} image-mode-winprops result: (t (info . Page 1 of 1337.
) (page . 1) (overlay . #<overlay from 1 to 7030463 in GNU Emacs Lisp Reference Manual_ For Emacs - Bil Lewis.pdf>))
::::::} image-mode-window-put result: ((image image :type png :file /tmp/docview1000/GNU Emacs Lisp Reference Manual_ For Emacs - Bil Lewis.pdf-dce847ffdfa273bf0fc346f8c3c5927a/page-1.png :scale 1 :pointer arrow :width 850 :transform-smoothing t) (info . Page 1 of 1337.
) (page . 1) (overlay . #<overlay from 1 to 7030463 in GNU Emacs Lisp Reference Manual_ For Emacs - Bil Lewis.pdf>))
:::::} image-mode-window-put result: ((image image :type png :file /tmp/docview1000/GNU Emacs Lisp Reference Manual_ For Emacs - Bil Lewis.pdf-dce847ffdfa273bf0fc346f8c3c5927a/page-1.png :scale 1 :pointer arrow :width 850 :transform-smoothing t) (info . Page 1 of 1337.
) (page . 1) (overlay . #<overlay from 1 to 7030463 in GNU Emacs Lisp Reference Manual_ For Emacs - Bil Lewis.pdf>))
:::::{ image-mode-window-get args: (hscroll #<window 3 on GNU Emacs Lisp Reference Manual_ For Emacs - Bil Lewis.pdf>)
::::::{ image-mode-winprops args: (#<window 3 on GNU Emacs Lisp Reference Manual_ For Emacs - Bil Lewis.pdf> nil)
::::::} image-mode-winprops result: (#<window 3 on GNU Emacs Lisp Reference Manual_ For Emacs - Bil Lewis.pdf> (image image :type png :file /tmp/docview1000/GNU Emacs Lisp Reference Manual_ For Emacs - Bil Lewis.pdf-dce847ffdfa273bf0fc346f8c3c5927a/page-1.png :scale 1 :pointer arrow :width 850 :transform-smoothing t) (info . Page 1 of 1337.
) (page . 1) (overlay . #<overlay from 1 to 7030463 in GNU Emacs Lisp Reference Manual_ For Emacs - Bil Lewis.pdf>))
:::::} image-mode-window-get result: nil
:::::{ image-mode-window-get args: (vscroll #<window 3 on GNU Emacs Lisp Reference Manual_ For Emacs - Bil Lewis.pdf>)
::::::{ image-mode-winprops args: (#<window 3 on GNU Emacs Lisp Reference Manual_ For Emacs - Bil Lewis.pdf> nil)
::::::} image-mode-winprops result: (#<window 3 on GNU Emacs Lisp Reference Manual_ For Emacs - Bil Lewis.pdf> (image image :type png :file /tmp/docview1000/GNU Emacs Lisp Reference Manual_ For Emacs - Bil Lewis.pdf-dce847ffdfa273bf0fc346f8c3c5927a/page-1.png :scale 1 :pointer arrow :width 850 :transform-smoothing t) (info . Page 1 of 1337.
) (page . 1) (overlay . #<overlay from 1 to 7030463 in GNU Emacs Lisp Reference Manual_ For Emacs - Bil Lewis.pdf>))
:::::} image-mode-window-get result: nil
::::} doc-view-insert-image result: nil
::::{ image-mode-window-get args: (overlay nil)
:::::{ image-mode-winprops args: (nil nil)
:::::} image-mode-winprops result: (#<window 3 on GNU Emacs Lisp Reference Manual_ For Emacs - Bil Lewis.pdf> (image image :type png :file /tmp/docview1000/GNU Emacs Lisp Reference Manual_ For Emacs - Bil Lewis.pdf-dce847ffdfa273bf0fc346f8c3c5927a/page-1.png :scale 1 :pointer arrow :width 850 :transform-smoothing t) (info . Page 1 of 1337.
) (page . 1) (overlay . #<overlay from 1 to 7030463 in GNU Emacs Lisp Reference Manual_ For Emacs - Bil Lewis.pdf>))
::::} image-mode-window-get result: #<overlay from 1 to 7030463 in GNU Emacs Lisp Reference Manual_ For Emacs - Bil Lewis.pdf>
::::{ image-mode-window-get args: (info nil)
:::::{ image-mode-winprops args: (nil nil)
:::::} image-mode-winprops result: (#<window 3 on GNU Emacs Lisp Reference Manual_ For Emacs - Bil Lewis.pdf> (image image :type png :file /tmp/docview1000/GNU Emacs Lisp Reference Manual_ For Emacs - Bil Lewis.pdf-dce847ffdfa273bf0fc346f8c3c5927a/page-1.png :scale 1 :pointer arrow :width 850 :transform-smoothing t) (info . Page 1 of 1337.
) (page . 1) (overlay . #<overlay from 1 to 7030463 in GNU Emacs Lisp Reference Manual_ For Emacs - Bil Lewis.pdf>))
::::} image-mode-window-get result: Page 1 of 1337.

:::} doc-view-goto-page result: Page 1 of 1337.

::} doc-view-new-window-function result: Page 1 of 1337.

:} image-mode-winprops result: (#<window 3 on GNU Emacs Lisp Reference Manual_ For Emacs - Bil Lewis.pdf> (image image :type png :file /tmp/docview1000/GNU Emacs Lisp Reference Manual_ For Emacs - Bil Lewis.pdf-dce847ffdfa273bf0fc346f8c3c5927a/page-1.png :scale 1 :pointer arrow :width 850 :transform-smoothing t) (info . Page 1 of 1337.
) (page . 1) (overlay . #<overlay from 1 to 7030463 in GNU Emacs Lisp Reference Manual_ For Emacs - Bil Lewis.pdf>))
:{ image-mode-window-get args: (hscroll (#<window 3 on GNU Emacs Lisp Reference Manual_ For Emacs - Bil Lewis.pdf> (image image :type png :file /tmp/docview1000/GNU Emacs Lisp Reference Manual_ For Emacs - Bil Lewis.pdf-dce847ffdfa273bf0fc346f8c3c5927a/page-1.png :scale 1 :pointer arrow :width 850 :transform-smoothing t) (info . Page 1 of 1337.
) (page . 1) (overlay . #<overlay from 1 to 7030463 in GNU Emacs Lisp Reference Manual_ For Emacs - Bil Lewis.pdf>)))
:} image-mode-window-get result: nil
:{ image-mode-window-get args: (vscroll (#<window 3 on GNU Emacs Lisp Reference Manual_ For Emacs - Bil Lewis.pdf> (image image :type png :file /tmp/docview1000/GNU Emacs Lisp Reference Manual_ For Emacs - Bil Lewis.pdf-dce847ffdfa273bf0fc346f8c3c5927a/page-1.png :scale 1 :pointer arrow :width 850 :transform-smoothing t) (info . Page 1 of 1337.
) (page . 1) (overlay . #<overlay from 1 to 7030463 in GNU Emacs Lisp Reference Manual_ For Emacs - Bil Lewis.pdf>)))
:} image-mode-window-get result: nil
:{ image-get-display-property args: nil
:} image-get-display-property result: (image :type png :file /tmp/docview1000/GNU Emacs Lisp Reference Manual_ For Emacs - Bil Lewis.pdf-dce847ffdfa273bf0fc346f8c3c5927a/page-1.png :scale 1 :pointer arrow :width 850 :transform-smoothing t)
} image-mode-reapply-winprops result: nil
{ image-mode-window-get args: (page nil)
:{ image-mode-winprops args: (nil nil)
:} image-mode-winprops result: (#<window 3 on GNU Emacs Lisp Reference Manual_ For Emacs - Bil Lewis.pdf> (image image :type png :file /tmp/docview1000/GNU Emacs Lisp Reference Manual_ For Emacs - Bil Lewis.pdf-dce847ffdfa273bf0fc346f8c3c5927a/page-1.png :scale 1 :pointer arrow :width 850 :transform-smoothing t) (info . Page 1 of 1337.
) (page . 1) (overlay . #<overlay from 1 to 7030463 in GNU Emacs Lisp Reference Manual_ For Emacs - Bil Lewis.pdf>))
} image-mode-window-get result: 1
{ doc-view-last-page-number args: nil
} doc-view-last-page-number result: 1337
{ image-mode-reapply-winprops args: nil
:{ image-mode-winprops args: (nil t)
::{ edebug-anon1613 args: ((#<window 3 on GNU Emacs Lisp Reference Manual_ For Emacs - Bil Lewis.pdf> (image image :type png :file /tmp/docview1000/GNU Emacs Lisp Reference Manual_ For Emacs - Bil Lewis.pdf-dce847ffdfa273bf0fc346f8c3c5927a/page-1.png :scale 1 :pointer arrow :width 850 :transform-smoothing t) (info . Page 1 of 1337.
) (page . 1) (overlay . #<overlay from 1 to 7030463 in GNU Emacs Lisp Reference Manual_ For Emacs - Bil Lewis.pdf>)))
::} edebug-anon1613 result: (#<window 3 on GNU Emacs Lisp Reference Manual_ For Emacs - Bil Lewis.pdf> (image image :type png :file /tmp/docview1000/GNU Emacs Lisp Reference Manual_ For Emacs - Bil Lewis.pdf-dce847ffdfa273bf0fc346f8c3c5927a/page-1.png :scale 1 :pointer arrow :width 850 :transform-smoothing t) (info . Page 1 of 1337.
) (page . 1) (overlay . #<overlay from 1 to 7030463 in GNU Emacs Lisp Reference Manual_ For Emacs - Bil Lewis.pdf>))
::{ edebug-anon1613 args: ((t (image image :type png :file /tmp/docview1000/GNU Emacs Lisp Reference Manual_ For Emacs - Bil Lewis.pdf-dce847ffdfa273bf0fc346f8c3c5927a/page-1.png :scale 1 :pointer arrow :width 850 :transform-smoothing t) (info . Page 1 of 1337.
) (page . 1) (overlay . #<overlay from 1 to 7030463 in GNU Emacs Lisp Reference Manual_ For Emacs - Bil Lewis.pdf>)))
::} edebug-anon1613 result: (t (image image :type png :file /tmp/docview1000/GNU Emacs Lisp Reference Manual_ For Emacs - Bil Lewis.pdf-dce847ffdfa273bf0fc346f8c3c5927a/page-1.png :scale 1 :pointer arrow :width 850 :transform-smoothing t) (info . Page 1 of 1337.
) (page . 1) (overlay . #<overlay from 1 to 7030463 in GNU Emacs Lisp Reference Manual_ For Emacs - Bil Lewis.pdf>))
:} image-mode-winprops result: (#<window 3 on GNU Emacs Lisp Reference Manual_ For Emacs - Bil Lewis.pdf> (image image :type png :file /tmp/docview1000/GNU Emacs Lisp Reference Manual_ For Emacs - Bil Lewis.pdf-dce847ffdfa273bf0fc346f8c3c5927a/page-1.png :scale 1 :pointer arrow :width 850 :transform-smoothing t) (info . Page 1 of 1337.
) (page . 1) (overlay . #<overlay from 1 to 7030463 in GNU Emacs Lisp Reference Manual_ For Emacs - Bil Lewis.pdf>))
:{ image-mode-window-get args: (hscroll (#<window 3 on GNU Emacs Lisp Reference Manual_ For Emacs - Bil Lewis.pdf> (image image :type png :file /tmp/docview1000/GNU Emacs Lisp Reference Manual_ For Emacs - Bil Lewis.pdf-dce847ffdfa273bf0fc346f8c3c5927a/page-1.png :scale 1 :pointer arrow :width 850 :transform-smoothing t) (info . Page 1 of 1337.
) (page . 1) (overlay . #<overlay from 1 to 7030463 in GNU Emacs Lisp Reference Manual_ For Emacs - Bil Lewis.pdf>)))
:} image-mode-window-get result: nil
:{ image-mode-window-get args: (vscroll (#<window 3 on GNU Emacs Lisp Reference Manual_ For Emacs - Bil Lewis.pdf> (image image :type png :file /tmp/docview1000/GNU Emacs Lisp Reference Manual_ For Emacs - Bil Lewis.pdf-dce847ffdfa273bf0fc346f8c3c5927a/page-1.png :scale 1 :pointer arrow :width 850 :transform-smoothing t) (info . Page 1 of 1337.
) (page . 1) (overlay . #<overlay from 1 to 7030463 in GNU Emacs Lisp Reference Manual_ For Emacs - Bil Lewis.pdf>)))
:} image-mode-window-get result: nil
:{ image-get-display-property args: nil
:} image-get-display-property result: (image :type png :file /tmp/docview1000/GNU Emacs Lisp Reference Manual_ For Emacs - Bil Lewis.pdf-dce847ffdfa273bf0fc346f8c3c5927a/page-1.png :scale 1 :pointer arrow :width 850 :transform-smoothing t)
} image-mode-reapply-winprops result: nil
{ image-mode-window-get args: (page nil)
:{ image-mode-winprops args: (nil nil)
:} image-mode-winprops result: (#<window 3 on GNU Emacs Lisp Reference Manual_ For Emacs - Bil Lewis.pdf> (image image :type png :file /tmp/docview1000/GNU Emacs Lisp Reference Manual_ For Emacs - Bil Lewis.pdf-dce847ffdfa273bf0fc346f8c3c5927a/page-1.png :scale 1 :pointer arrow :width 850 :transform-smoothing t) (info . Page 1 of 1337.
) (page . 1) (overlay . #<overlay from 1 to 7030463 in GNU Emacs Lisp Reference Manual_ For Emacs - Bil Lewis.pdf>))
} image-mode-window-get result: 1
{ doc-view-last-page-number args: nil
} doc-view-last-page-number result: 1337

When we dissect the doc-view-mode function, for most forms it seems quite straightforward to infer its functionality. The lesser straightforward forms are the ones that involve the display functionalities. Relevant for the display functionalities are:

(add-hook 'image-mode-new-window-functions
          #'doc-view-new-window-function nil t)

(image-mode-setup-winprops)

(doc-view-initiate-display)

The first form simply adds a function to the image-mode-new-window-functions which gets triggered from the image-mode-winprops function.

The second form, sets the image-mode-winprops-alist to nil and adds image-mode-reapply-winprops tot the window-configuration-change-hook. This functions simply restores the ‘vscroll and ‘hscroll after a window configuration change.

The third form triggers the displaying. The display mechanism is rather elaborate, so we will dissect it in here.

The doc-view-initiate-display function starts with calling doc-view-buffer-message. Despite the simple name (and purpose) of the function, the function has a noteworthy side-effects:

• because it calls image-mode-window-get (through doc-view-current-overlay), it calls image-mode-winprops, which first sets winprops anf image-mode-winprops-alist to (t) and ((t)) and then triggers doc-view-new-window-function (by running the hook).
• the doc-view-new-window-function creates an overlay over the entire content and adds the properties ~’doc-view t~, ~’window (car winprops)~ (which is t the first time), but then when called for the first time, it again deletes the overlay. Finally it adds it to the winprops. (When the car of winprops is not t, has a string overlay property, and the doc-view--current-converter-processes is nil, then it also jumps to the ‘current’ page.

NOTE ON COPYRIGHT YEARS

In copyright notices where the copyright holder is the Free Software Foundation, then where a range of years appears, this is an inclusive range that applies to every year in the range. For example: 2005-2008 represents the years 2005, 2006, 2007, and 2008.

This file is part of GNU Emacs.

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