Protesilaos Stavrou

Emacs: dired-preview version 0.4.0

This is a simple package to automatically preview in a window the file at point in Dired buffers. Preview windows are closed when they are no longer relevant, while preview buffers are killed if they have not been used for other purposes beside previewing. The package provides several customisation options to control its behaviour.

Below are the release notes

Version 0.4.0 on 2025-02-18

This version contains several refinements and bug fixes.

Preview buffers have a mode line indicator

Preview buffers have a prefix to their name to make them stand out. This is controlled by the user option dired-preview-buffer-name-indicator, which is a string that defaults to [P].

Control how preview buffers are cleaned up

The way dired-preview works is to display a buffer and then keep a list of preview buffers to economise on redisplaying it again. This list of buffers is relevant for as long as we are in the Dired buffer, otherwise all buffers therein are killed (buffers that were alive before being previewed are not touched).

By default we delete from oldest to newest the accumulated buffers when they exceed 10 in total. Though users can modify this behaviour by editing the value of the new user option dired-preview-kill-buffers-method (its doc string explains the technicalities).

Thanks to artelse for discussing this with me in issue 20: https://github.com/protesilaos/dired-preview/issues/20.

The dired-preview-display-action-alist has a new optional function

The dired-preview-display-action-alist is the user option which controls where the preview window is displayed. Its value can either be the symbol of a function or a display-buffer-alist entry.

By default, we have a “do-what-I-mean” function that tries to find a good placement for the window. The new dired-preview-display-action-alist-below function has a straightforward behaviour: it always shows the preview below the current window and it always makes the preview window 0.3 times the height of the Emacs frame.

Encypted files are no longer previewed

This is to ensure that potentially sensitive contents are not displayed by accident, such as during a video call.

We no longer preview the “self” directory

We should not trigger a preview when the cursor is over the implicit . directory, as that causes a recursion that breaks things. Thanks to Inkbottle007 for reporting the bug in issue 23: https://github.com/protesilaos/dired-preview/issues/23.

Miscellaneous

  • Fixed a scenario where we would try to delete the last available window on the current frame. This should never happen. Thanks to artelse for reporting a relevant bug in the discussion of issue 22: https://github.com/protesilaos/dired-preview/issues/22.

  • Fixed a case when hexl-follow-ascii could fail to find an overlay under certain conditions. This did not create any noticeable problems, though having an error there would interfere with any workflow that would rely on toggle-debug-on-error.

  • The preview window will automatically be closed if the user switches outside the given Dired buffer. We now do not consider a change to the minibuffer as being “outside” this context. This way, a quick M-x to, say, enable a minor mode does not have any effect on the window layout.

  • Suppressed the messaging facility of the underlying tracking of preview buffers. Otherwise, Dired would notify us that the directory has changed whenever we would preview a new one, which is superfluous.

  • The body of the dired-preview-trigger function, which determines whether a preview will be displayed, is encapsulated in a condition-case. This helps capture errors and thus have a more predictable behaviour.

  • The dired-preview-display-action-alist has a more accurate declaration which allows for its correct customisation inside the Custom UI interface. In particular, it will behave the same way as the display-buffer-alist, where relevant.

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