Homepage: https://www.gnu.org/software/emacs
Author: Richard Sharman
Minor mode displaying buffer changes with special face
A minor mode: "Highlight Changes mode".
When Highlight Changes mode is enabled changes to the buffer are
recorded with a text property. Normally these ranges of text are
displayed in a distinctive face. However, sometimes it is
desirable to temporarily not see these changes. Instead of
disabling Highlight Changes mode (which would remove the text property)
use the command highlight-changes-visible-mode.
Two faces are supported: one for changed or inserted text and
another for the first character after text has been deleted.
When Highlight Changes mode is on (even if changes are not visible)
you can go to the next or previous change with
`highlight-changes-next-change' or `highlight-changes-previous-change'.
Command highlight-compare-with-file shows changes in this file
compared with another file (by default the previous version of the
file).
The command highlight-compare-buffers compares two buffers by
highlighting their differences.
You can "age" different sets of changes by using
`highlight-changes-rotate-faces'. This rotates through a series
of different faces, so you can distinguish "new" changes from "older"
changes. You can customize these "rotated" faces in two ways. You can
either explicitly define each face by customizing
`highlight-changes-face-list'. If, however, the faces differ from
`highlight-changes-face' only in the foreground color, you can simply set
`highlight-changes-colors'. If `highlight-changes-face-list' is nil when
the faces are required they will be constructed from
`highlight-changes-colors'.
You can automatically rotate faces when the buffer is saved;
see function `highlight-changes-rotate-faces' for how to do this.
The hook `highlight-changes-mode-hook' is called when
Highlight Changes mode is turned on or off.
When it called, variable `highlight-changes-mode' has been updated
to the new value.
Example usage:
(defun my-highlight-changes-mode-hook ()
(if highlight-changes-mode
(add-hook 'write-file-functions 'highlight-changes-rotate-faces nil t)
(remove-hook 'write-file-functions 'highlight-changes-rotate-faces t)))
Automatically enabling Highlight Changes mode
Normally, Highlight Changes mode is turned on explicitly in a buffer.
If you prefer to have it automatically invoked you can do it as
follows.
1. Most modes have a major-hook, typically called MODE-hook. You
can use `add-hook' to call `highlight-changes-mode'.
Example:
(add-hook 'c-mode-hook 'highlight-changes-mode)
However, this cannot be done for Fundamental mode for there is no
such hook.
2. You can use the function `global-highlight-changes-mode'
This function, which is fashioned after the way `global-font-lock' works,
toggles on or off global Highlight Changes mode. When activated, it turns
on Highlight Changes mode in all "suitable" existing buffers and will turn
it on in new "suitable" buffers to be created.
A buffer's "suitability" is determined by variable
`highlight-changes-global-modes', as follows. If it is
* nil -- then no buffers are suitable;
* a function -- this function is called and the result is used. As
an example, if the value is `buffer-file-name' then all buffers
who are visiting files are suitable, but others (like Dired
buffers) are not;
* a list -- then the buffer is suitable if and only if its mode is in the
list, except if the first element is `not', in which case the test
is reversed (i.e. it is a list of unsuitable modes).
* Otherwise, the buffer is suitable if its name does not begin with
` ' or `*' and if `buffer-file-name' returns true.
To enable it for future sessions put this in your ~/.emacs file:
(global-highlight-changes-mode t)
Possible bindings:
(global-set-key '[C-right] #'highlight-changes-next-change)
(global-set-key '[C-left] #'highlight-changes-previous-change)
Other interactive functions (that could be bound if desired):
`highlight-changes-mode'
`highlight-changes-remove-highlight'
`highlight-compare-with-file'
`highlight-compare-buffers'
`highlight-changes-rotate-faces'