A lightweight scrollbar for the Emacs mode line.
For graphical window systems:
and in terminals:
Emacs has so many great ways to navigate, I really only ever used scrollbars as a visual indication of position and file size. But recently, to save space, I added (scroll-bar-mode -1)
to my init. Immediately I missed having that information at a glance. A percentage in the mode line (like 25%
) is not very glanceable, and also gives no information about the current showing content relative to the total line length (i.e. the length of the bar). I wanted something very fast and very light weight, plus I'm not so into rainbow cats. Hence MLScroll.
- Uses specified space for drawing (only 3 variable-width spaces, actually) for lightning-fast text-based mode line scroll.
- Conveys the number of lines above/visible/below window. Computes line numbers with caching for performance.
- Works in terminals! Terminal graphics are more granular (the minimum "pixel" is a character wide). You might want to increase
mlscroll-width-chars
there. - In graphical Emacs, you can interact with the mode line scroll bar — click, click + drag, and wheel-scroll a full window height at a time.
- Clicking on an inactive window's mode line scroll bar does not activate that window.
- By default, MLScroll disables the
XX%
position mode line indication. - By default, MLScroll puts itself in the mode line variable
mode-line-end-spaces
, prepending a spacer to right align itself. Optionally, it can instead replace theXX%
indicator (or be placed anywhere in your mode line). - Use
M-x customize-group mlscroll
to change background colors, overall scroll bar width, minimum current "thumb" width, border size, and other settings. which-function-mode
by default puts[full-function-name]
on the right of the mode line. With long names this can push the scroll bar off the right side of the mode line. Setmlscroll-shortfun-min-width
to a minimum width, and MLScroll will truncate the function name to at least that many trailing characters ([…function-name]
or similar).
The MLScroll bar widths are based on the number of lines visible in the window (+ lines before and after it). The normal scroll bar is based on characters shown. Both tend to change as very long/wrapped lines come into view, but in the opposite sense: MLScroll sees fewer lines shown and shrinks the current thumb; the default scrollbar sees many characters come in view, and grows it. I find the lines approach to be more sensible, and it has the advantage that with truncate-lines
on, the thumb doesn't change size as you scroll. If you'd like to see the difference, evaluate (insert (make-string 5000 ?a) "\n")
in the *scratch*
buffer amidst other normal text, and scroll through before and after toggle-truncate-lines
. On the other hand, highly folded documents like org-mode docs will show a changing "thumb size" as you scroll through, as the current window could contain main (hidden) lines. I find that pretty convenient actually.
Get it from MELPA, and arrange to have
(mlscroll-mode 1)
called at init time (or whenever you are feeling scrolly). Toggle on or off anytime. Example for use-package
:
(use-package mlscroll
:ensure t
:config
(setq mlscroll-shortfun-min-width 11) ;truncate which-func, for default mode-line-format's
(mlscroll-mode 1))
Alternatively, if you start emacs using the command line --daemon
command (see below):
(use-package mlscroll
:ensure t
:hook (server-after-make-frame . mlscroll-mode))
Note that MLScroll is most visually compatible with "plain" mode line formats that don't use :box
bordering. It will warn you if you try to use a border with a :box
-full format enabled. It also doesn't inherit :underline
and :overline
mode line properties unless mlscroll-border
is set to 0 (these don't work with the combination of specified space and :box
).
See the suggestions for configuring moody for some config ideas.
-
How does it work? MLScroll places itself by default in
mode-line-end-spaces
, and uses a right-aligned space to align it at the end of the modeline. -
MLScroll doesn't work with my fancy mode line mode! It should work automatically for simple mode lines that end in
mode-line-end-spaces
. If you prefer, setmlscroll-right-align
tonil
andmlscroll-alter-percent-position
to'replace
to put it in place of theXX%
percentage indicator. Otherwise, e.g. if you have a highly customized or pre-packaged mode line, you'll need to find somewhere to put MLScroll. A general recipe is to:- Set
mlscroll-right-align
tonil
. - Set the mode line scroller into the relevant mode-line variable directly yourself, like so:
(setq fancy-mode-line-variable-of-some-kind '(:eval (mlscroll-mode-line))
. - Alternatively, if you didn't design your mode line yourself or find this too complicated, ask whoever did to support MLScroll.
- Set
-
MLScroll starts off very small when I start an emacs session using
--daemon
. For graphical windows, MLScroll needs to know the width of font characters in the mode line (or at least the default font) to draw a pixel-perfect bar. Since--daemon
doesn't create a frame or know anything about the font widths, loading MLScroll directly under a--daemon
session misreports the font width as 1 pixel, leading to a very small scroller bar. The solution is either to abandon--daemon
in favor of(server-start)
in your init file, or arrange for MLScroll to be initialized later, after a frame is created, ala:(use-package mlscroll :hook (server-after-make-frame . mlscroll-mode))
-
I'm getting errors about mode-line-misc-info: You probably have
mlscroll-shortfun-min-width
set to non-nil
with a non-standard mode line format. Function name shortening relies on dividing the mode line atmode-line-misc-info
and computing how much space it takes, then alteringwhich-func-format
(inside ofmode-line-misc-info
) to truncate the function name appropriately. -
How can I customize MLScroll?
M-x customize-group mlscroll [Ret]
. -
I get a message about :box disabling my MLScroll border: MLScroll uses the
:box
attribute to draw border. If your normal mode line face already has a:box
property, this will interfere and cause the left/right border to show up. If you want a border to make your MLScroll smaller, consider disabling the:box
property on faces'mode-line
and'mode-line-inactive
(M-x customized-group mode-line-faces [Ret]
). See issue.
MLScroll takes up a decent (configurable) chunk of your mode line. To save space for it even when the window is somewhat narrow, I use:
- minions to hide all minor-modes under a nice menu.
- cyphejor to shorten the names of major mode using emoji and greek characters.
(setq mlscroll-shortfun-min-width 11)
to trim down the which-function name as needed.- removal of mule-info, and a trim of all double-spaces anywhere in the mode line format to a single space:
(setq-default
mode-line-format ;less space, no MULE
(cl-nsubst-if " " (lambda (x) (and (stringp x) (string-blank-p x) (> (length x) 1)))
(remove 'mode-line-mule-info mode-line-format))))