Scroll on Jump

This package allows you to control the scrolling on any operation that jumps to a new location.

• Re-centers vertical scrolling.
• Optionally animate the scroll using a fixed time limit.

Since this might not always be desired, this can be applied using advice or individual key bindings, if you prefer to limit the changes to certain shortcuts.

Available via melpa.

See demo video.

Motivation

Actions that move the point may move the cursor to the edge of the screen, while having a large scroll-margin can help, this isn't always convenient as it can be useful to move the cursor to the screen edge.

Features

Animated Scrolling

You can optionally jump to the new location in multiple steps (lines/pixels) this can help to give context when moving around the document.

Responsive Animation

To avoid animation display slowing you down - any input will cancel the animation so multiple key strokes won't lag behind display updates.

Un-intrusive

This only exposes functionality you can make use of, without interfering with anything you don't want it to.

Usage

The following functions are exposed.

scroll-on-jump

Macro that behaves like progn, any code that runs in the body of this macro will perform scrolling when moving the point.

scroll-on-jump-interactive

Use this to wrap interactive function (intended to be used in key bindings).

scroll-on-jump-advice-add

Adds advice so scrolling is performed whenever the function is called.

scroll-on-jump-advice-remove

Remove the advice added to the function.

Commands that work well include:

• Jump to search result, paragraph, function ... etc.
• Undo/redo.
• Go to declaration.

Wrapping Commands That Scroll

If a command it's self sets a new scroll location, these can be wrapped using scroll-on-jump-with-scroll- prefix, so scroll-on-jump-with-scroll-interactive, scroll-on-jump-with-scroll-advice-add .. etc.

In this case the newly set scroll location will be used when displaying the animation.

Key Binding Example

Take this example of pressing Ctrl-Z for undo.

Using scroll-on-jump-interactive makes this use scrol-on-jump features.

Before:

(global-set-key (kbd "<C-z>") 'undo)

After:

(global-set-key (kbd "<C-z>") (scroll-on-jump-interactive 'undo))

Advice Example

Use this with care, since it advises all uses of the function.

(scroll-on-jump-advice-add forward-paragraph)
(scroll-on-jump-advice-add backward-paragraph)

Macro Example

When already using a lambda in a key-binding, it's simplest to wrap this in a macro.

Before:

(global-set-key (kbd "<f12>")
  (lambda () (interactive) (my-function)))

After:

(global-set-key (kbd "<f12>")
  (lambda () (interactive) (scroll-on-jump (my-function))))

Complete Example

Here is a more complete example for evil-mode users.

(with-eval-after-load 'evil
  (scroll-on-jump-advice-add evil-undo)
  (scroll-on-jump-advice-add evil-redo)
  (scroll-on-jump-advice-add evil-jump-item)
  (scroll-on-jump-advice-add evil-jump-forward)
  (scroll-on-jump-advice-add evil-jump-backward)
  (scroll-on-jump-advice-add evil-ex-search-next)
  (scroll-on-jump-advice-add evil-ex-search-previous)
  (scroll-on-jump-advice-add evil-forward-paragraph)
  (scroll-on-jump-advice-add evil-backward-paragraph)
  (scroll-on-jump-advice-add evil-goto-mark)

  ;; Actions that themselves scroll.
  (scroll-on-jump-with-scroll-advice-add evil-goto-line)
  (scroll-on-jump-with-scroll-advice-add evil-scroll-down)
  (scroll-on-jump-with-scroll-advice-add evil-scroll-up)
  (scroll-on-jump-with-scroll-advice-add evil-scroll-line-to-center)
  (scroll-on-jump-with-scroll-advice-add evil-scroll-line-to-top)
  (scroll-on-jump-with-scroll-advice-add evil-scroll-line-to-bottom))

(with-eval-after-load 'goto-chg
  (scroll-on-jump-advice-add goto-last-change)
  (scroll-on-jump-advice-add goto-last-change-reverse))

(global-set-key (kbd "<C-M-next>") (scroll-on-jump-interactive 'diff-hl-next-hunk))
(global-set-key (kbd "<C-M-prior>") (scroll-on-jump-interactive 'diff-hl-previous-hunk))

Customization

While the defaults seem to work well, these values can be customized.

scroll-on-jump-duration: 0.4

The duration (in seconds) for jumping to take, set to 0.0 to jump immediately.

scroll-on-jump-smooth: t

When not nil, use smooth scrolling (by pixels), otherwise scroll by lines.

scroll-on-jump-curve: 'smooth

Apply a curve to the scroll speed, starting and ending slow.

'smooth:	Ease in/out.
'smooth-in:	Ease in (end slow).
'smooth-out:	Ease in (start slow).
'linear:	Linear motion (no easing).

scroll-on-jump-curve-power: 3.0

The strength of the curve (when non-linear).

Values between 2 and 8 work well.

• Below 2.0 approaches a linear curve.
• Above 8.0 can make the motion overly abrupt.

scroll-on-jump-mode-line-format: nil

When non-nil, use this value for the mode-line-format while scrolling. This can be used to temporarily override the mode-line while scrolling. It can also help to avoid overly complex mode-lines from slowing down scrolling.

Installation

Until this is available on melpa, straight can be used to install this package.

(use-package scroll-on-jump
  :config
  (setq scroll-on-jump-duration 0.6))

Limitations

• Any commands that themselves scroll to a new location and modify the buffer will not work as expected (they may scroll too far for example).