image-roll.el

This package provides a virtual scroll engine for displaying books/documents in Emacs. The main purpose of the package is to provide a continuous scrolling feature when viewing documents. This is the successor of the pdf-continuous-scroll-mode package. Making it a new package (instead of an update), was necessarry because this package provides a general ‘display engine’ which can be used also by other packages, like doc-view.

This implementation of the image-roll/continuous-scroll is based on a correct usage of vscroll, instead of using the vscroll functionality incorrectly (causing Emacs crashes when viewing large documents, see this thread in the Emacs devel archives). Additionally, this implementation is quite a bit simpler and cleaner than previous implementations (e.g. the gap-overlays have been eliminated).

The package is meant to be used in combination with some other package that provides features to extract and manage the data from the document. An example of such a package is the pdf-tools package as provided in the the pdf-roll branch of my pdf-tools repo.

The package is written in a way that it supports images/pages of different sizes on the same roll (see comment above `image-roll-scroll-forward’). Also there is no minumum or maximum on the range of the sizes, and finally, it is written to support being displayed in (any number of) multiple windows.

This file provides four buffer local variables that should be set to the values of the functions that correctly ‘retrieve’ the required data from the document. See their docstrings and the `image-roll-directory’ function (or `pdf-scroll.el’) for more info.

The core functionality, i.e. the ‘scroll’ is provided by the `image-roll–new-window-function’ and `image-roll–redisplay’ functions. The function `image-roll–new-window-function’ should be added to the `image-mode-new-window-functions’ while the `image-roll–redisplay’ should be added to the `window-configuration-change-hook’ both as buffer local hook functions (i.e. by passing a non-nil LOCAL argument to `add-hook’). For the `image-mode-new-window-functions’ to have effect, the `image-mode-winprops’ should be initialized by either using `image-mode-setup-winprops’ (like in the body of `pdf-view-mode’) or by initializing the `image-mode-winprops-alist’ explicitly (by setting its value to nil, like in the `image-roll-mode’ example).

Donations

Donations are more than welcome, as I have been working many weeks/months on this feature for zero, while I can not even afford to buy new socks without holes. Thank you very much!

Known issues

dalanicolai#4

Todo

• See if we can cache page images in advance.
• Add support for ‘sliced’ images (in particular for pdf-view-set-slice-from-bounding-box)

Installation and usage

Because there is still the issue, described just above, left, I am not yet publishing this package on some package archive (or submit it to get included into Emacs core). Therefore, it is up to you how you install this package, of which the simplest way is to clone this repo or download the image-roll.el file, and load it from you init file.

This does not provide any useful functionality by itself, but instead it is meant to be used by some other package (see below).

Spacemacs users

Simply clone the private layer here, then restart Spacemacs and update your packages. Finally, from within a pdf buffer press c to activate displaying using the image-roll.

Doom users

Don’t use the pdf module, and add the following code to packages.el:

(package! pdf-tools :recipe
          (:host github
                 :repo "dalanicolai/pdf-tools"
                 :branch "pdf-roll"
                 :files ("lisp/*.el"
                         "README"
                         ("build" "Makefile")
                         ("build" "server")
                         (:exclude "lisp/tablist.el" "lisp/tablist-filter.el"))))

(package! image-roll :recipe
          (:host github
                 :repo "dalanicolai/image-roll.el"))

then manually remove the old pdf-tools directory using:

rm -rf ~/.emacs.d/.local/straight/repos/pdf-tools/

then run doom sync (should we add -u here? I am no Doom user).

Finally, from some pdf buffer do M-x pdf-view-roll-minor-mode to get continuous scrolling.

Install complementary packages (support)

pdf-tools

A pdf-tools branch that implements image-roll support is available in the pdf-roll branch of my pdf-tools fork. It is probably easiest to install it using quelpa or straight. I am a Spacemacs user, where I install the package (and also image-mode) using the following code:

(pdf-tools :location (recipe
                      :fetcher github
                      :repo "dalanicolai/pdf-tools"
                      :branch "pdf-roll"
                      :files ("lisp/*.el"
                              "README"
                              ("build" "Makefile")
                              ("build" "server")
                              (:exclude "lisp/tablist.el" "lisp/tablist-filter.el"))))
(image-roll :location (recipe
                       :fetcher github
                       :repo "dalanicolai/image-roll.el"))

From the above code example, I hope you are able to find out how to adapt it for quelpa/straight. Contributions, e.g. of installation instructions, are very welcome.

After successful installation, from a pdf buffer do M-x pdf-view-roll-minor-mode to toggle displaying using the image roll.

Because the image-roll package is not yet available from an archive, I am not creating a PR at pdf-tools yet.

doc-view

If you would like to also use the image-roll in doc-view, then simply download and load this doc-view.el file. After opening a file in doc-view, first WAIT UNTIL ALL PAGES HAVE BEEN CONVERTED (see page counter at bottom of screen). Subsequently do M-x doc-view-roll-minor-mode (for doc-view, currently only activation of the minor mode has been implemented).

New keybindings

Key binding	Description
S-next	Scroll full screen forward
S-prior	Scroll full screen backward

(next/prior = PgUp/PgDown)