#+SPDX-License-Identifier: GPL-3.0-or-later #+SPDX-FileCopyrightText: Copyright 2025 Free Software Foundation, Inc.
For us old neck beards, who learned to write software on punch cards and print out our code and output on wide line printers, it was helpful to have alternating bands of subtle background coloring to guide our eyes across the line on the page. Reading long rows of text across a 14 7/8” page, it was very easy to loose your place vertically while scanning the page horizontally. The subtle background shading was often done with pale bands of green alternating with the white of the paper.
Paper pre-printed with the pale green bars was often referred to as
“green bar” and the technique is also referred to as “zebra striping.”
In Emacs, in ps-print.el (PostScript print facility), the feature is
enabling with the ps-zebra-stripes setting.
To enable greenbar-mode in your comint-mode buffers, add the
following to your Emacs configuration:
(add-hook 'comint-mode-hook #'greenbar-mode)If you want to enable greenbar-mode only in a single mode derived
from comint-mode, then you need to add greenbar-mode only to the
desired derived mode hook. Adding greenbar-mode to
comint-mode-hook enables it for all comint derived modes.
The variable greenbar-color-theme is an Alist of predefined bar
background colors. Each element of the Alist consists of a symbol
that is the name of the theme; the rest of the list are color names
which are used as background colors for successive bands of lines.
The variable greenbar-color-list controls which set of color bars
are to be applied. The value is either a name from color theme
defined in greenbar-color-themes or it is a list of color names.
The variable greenbar-lines-per-bar controls how many output lines
are displayed using each band’s background color.
By default, input lines are not highlighted, but if
greenbar-highlight-input is set to a non-nil value, then input is
also highlighted with green bars as well.
Suggestions for other background color themes are always welcome.
Since this package is part of ELPA, it can be easily installed, and
then linking to comint buffers is easy.
(package-install 'greenbar)
(require 'greenbar)
(setopt greenbar-lines-per-bar 3
greenbar-background-colors 'greenbar
greenbar-highlight-input nil)
(add-hook 'comint-mode-hook #'greenbar-mode)Or, with use-package:
(use-package greenbar
:custom
(greenbar-lines-per-bar 3)
(greenbar-background-colors 'greenbar)
(greenbar-highlight-input nil)
:hook comint-mode)When you set greenbar-background-colors to greenbar
With a theme that has background-mode value of light, here’s what this
package will do to comint buffers.
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