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|
;;; ui-theme.el --- UI Theme Configuration and Persistence -*- lexical-binding: t; coding: utf-8; -*-
;; author: Craig Jennings <c@cjennings.net>
;;
;;; Commentary:
;; This module provides a theme management system with persistence across
;; Emacs sessions.
;;
;; - Theme selection via interactive interface (M-L)
;; - Automatic persistence of theme preference to a configurable file
;; - Safe theme loading with fallback mechanism
;; - Support for custom themes in the "themes" subdirectory
;;
;; The persistence mechanism saves theme choices to a file that can be
;; synchronized across machines, ensuring consistent appearance across
;; multiple computers.
;;; Code:
(require 'user-constants) ;; For org-dir
;; ----------------------------------- Themes ----------------------------------
;; theme choices and settings
;; downloaded custom themes go in themes subdirectory
(setq custom-safe-themes t) ;; trust all custom themes
(add-to-list 'custom-theme-load-path
(concat user-emacs-directory "themes"))
;; ------------------------------- Switch Themes -------------------------------
;; loads themes in completing read, then persists via the functions below
(defun cj/switch-themes ()
"Function to switch themes and save chosen theme name for persistence.
Unloads any other applied themes before applying the chosen theme."
(interactive)
(let ((chosentheme ""))
(setq chosentheme
(completing-read "Load custom theme: "
(mapcar #'symbol-name
(custom-available-themes))))
(mapc #'disable-theme custom-enabled-themes)
(load-theme (intern chosentheme) t))
(cj/save-theme-to-file))
(global-set-key (kbd "M-L") 'cj/switch-themes)
;; ----------------------------- Theme Persistence -----------------------------
;; persistence utility functions used by switch themes.
(defvar theme-file (concat org-dir "emacs-theme.persist")
"The location of the file to persist the theme name.
If you want your theme change to persist across instances, put this in a
directory that is sync'd across machines with this configuration.")
(defvar fallback-theme-name "modus-vivendi"
"The name of the theme to fallback on.
This is used then there's no file, or the theme name doesn't match
any of the installed themes. This should be a built-in theme. If theme name is
'nil', there will be no theme.")
(defun cj/read-file-contents (filename)
"Read FILENAME and return its content as a string.
If FILENAME isn't readable, return nil."
(when (file-readable-p filename)
(with-temp-buffer
(insert-file-contents filename)
(string-trim (buffer-string)))))
(defun cj/write-file-contents (content filename)
"Write CONTENT to FILENAME.
If FILENAME isn't writeable, return nil. If successful, return t."
(when (file-writable-p filename)
(condition-case err
(progn
(with-temp-buffer
(insert content)
(write-file filename))
t)
(error
(message "Error writing to %s: %s" filename (error-message-string err))
nil))))
(defun cj/get-active-theme-name ()
"Return the name of the active UI theme as a string.
Returns fallback-theme-name if no theme is active."
(if custom-enabled-themes
(symbol-name (car custom-enabled-themes))
fallback-theme-name))
(defun cj/save-theme-to-file ()
"Save the string representing the current theme to the theme-file."
(if (equal (cj/write-file-contents (cj/get-active-theme-name) theme-file) nil)
(message "Cannot save theme: %s is unwriteable" theme-file)
(message "%s theme saved to %s" (cj/get-active-theme-name) theme-file)))
(defun cj/load-fallback-theme (msg)
"Display MSG and load ui-theme fallback-theme-name.
Used to handle errors with loading persisted theme."
(message "%s Loading fallback theme %s" msg fallback-theme-name)
(load-theme (intern fallback-theme-name) t))
(defun cj/load-theme-from-file ()
"Apply the theme name contained in theme-file as the active UI theme.
If the theme is nil, it disables all current themes. If an error occurs
loading the file name, the fallback-theme-name is applied and saved."
(let ((theme-name (cj/read-file-contents theme-file)))
;; if theme-name is nil, unload all themes and load fallback theme
(if (not theme-name)
(progn
(mapc #'disable-theme custom-enabled-themes)
(cj/load-fallback-theme "Theme file not found or empty."))
;; Check if theme is 'nil' string
(if (string= theme-name "nil")
(mapc #'disable-theme custom-enabled-themes)
;; apply theme name or if error, load fallback theme
(condition-case err
(load-theme (intern theme-name) t)
(error
(cj/load-fallback-theme
(format "Error loading theme %s: %s."
theme-name (error-message-string err)))))))))
(cj/load-theme-from-file)
(provide 'ui-theme)
;;; ui-theme.el ends here
|
