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edited Jun 23 at 1:13

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(defun print-buffer-as-light-theme () "A command to print the buffer by temporarily applying a minimal light theme." (interactive) (let* ((print-theme-faces `((default ((t (:background "white" :foreground "black")))) (font-lock-comment-face ((t (:foreground "gray50")))) (font-lock-keyword-face ((t (:foreground "blue")))) (font-lock-string-face ((t (:foreground "purple")))) (font-lock-function-name-face ((t (:foreground "dark green")))) (font-lock-variable-name-face ((t (:foreground "saddle brown")))) (font-lock-type-face ((t (:foreground "teal")))) (font-lock-constant-face ((t (:foreground "dark violet")))))) (current-enabled-themes custom-enabled-themes)) (unwind-protect ;; --- TRY block: The main printing logic --- (progn (message "Applying temporary print theme...") (mapc #'disable-theme current-enabled-themes) (custom-theme-set-faces 'print-theme-temporary print-theme-faces) ;; The printing pipeline itself (which works fine on its own) (let* ((html-buffer (htmlize-buffer)) (html-content (with-current-buffer html-buffer (buffer-string))) (temp-html-file (make-temp-file "emacs-print-" nil ".html")) (temp-pdf-file (make-temp-file "emacs-print-" nil ".pdf")) (chrome-path "/Applications/Google Chrome.app/Contents/MacOS/Google Chrome") (lpr-command (format "lpr -o number-up=2 '%s'" temp-pdf-file))) (kill-buffer html-buffer) (unwind-protect (progn (with-temp-file temp-html-file (insert html-content)) (shell-command (format "'%s' --headless --print-to-pdf='%s' --no-pdf-header-footer 'file://%s'" chrome-path temp-pdf-file temp-html-file)) (shell-command lpr-command)) (when (file-exists-p temp-html-file) (delete-file temp-html-file)) (when (file-exists-p temp-pdf-file) (delete-file temp-pdf-file))) (message "Print job sent."))) ;; --- FINALLY block: Restore the original theme --- (progn (message "Restoring original theme...") ;; Unload the temporary print faces (custom-theme-set-faces 'print-theme-temporary) ;; Re-enable the original themes (mapc #'enable-theme current-enabled-themes)))))

(defun print-buffer-as-light-theme () "A command to print the buffer by temporarily applying a minimal light theme." (interactive) (let* ((print-theme-faces `((default ((t (:background "white" :foreground "black")))) (font-lock-comment-face ((t (:foreground "gray50")))) (font-lock-keyword-face ((t (:foreground "blue")))) (font-lock-string-face ((t (:foreground "purple")))) (font-lock-function-name-face ((t (:foreground "dark green")))) (font-lock-variable-name-face ((t (:foreground "saddle brown")))) (font-lock-type-face ((t (:foreground "teal")))) (font-lock-constant-face ((t (:foreground "dark violet")))))) (current-enabled-themes custom-enabled-themes)) (unwind-protect ;; --- TRY block: The main printing logic --- (progn (message "Applying temporary print theme...") (mapc #'disable-theme current-enabled-themes) (custom-theme-set-faces 'print-theme-temporary print-theme-faces) ;; The printing pipeline itself (which works fine on its own) (let* ((html-buffer (htmlize-buffer)) (html-content (with-current-buffer html-buffer (buffer-string))) (temp-html-file (make-temp-file "emacs-print-" nil ".html")) (temp-pdf-file (make-temp-file "emacs-print-" nil ".pdf")) (chrome-path "/Applications/Google Chrome.app/Contents/MacOS/Google Chrome") (lpr-command (format "lpr -o number-up=2 '%s'" temp-pdf-file))) (kill-buffer html-buffer) (unwind-protect (progn (with-temp-file temp-html-file (insert html-content)) (shell-command (format "'%s' --headless --print-to-pdf='%s' --no-pdf-header-footer 'file://%s'" chrome-path temp-pdf-file temp-html-file)) (shell-command lpr-command)) (when (file-exists-p temp-html-file) (delete-file temp-html-file)) (when (file-exists-p temp-pdf-file) (delete-file temp-pdf-file))) (message "Print job sent."))) ;; --- FINALLY block: Restore the original theme --- (progn (message "Restoring original theme...") ;; Unload the temporary print faces (custom-theme-set-faces 'print-theme-temporary) ;; Re-enable the original themes (mapc #'enable-theme current-enabled-themes)))))

What is the correct Emacs Lisp idiom to achieve this "temporary theme for printing" pattern? Specifically, how can I reliably apply a temporary set of faces, execute a command, and then guarantee that the original user theme is restored, without causing an "Unknown theme" error?

Thank you for your expertise.

(defun print-buffer-as-light-theme () "A command to print the buffer by temporarily applying a minimal light theme." (interactive) (let* ((print-theme-faces `((default ((t (:background "white" :foreground "black")))) (font-lock-comment-face ((t (:foreground "gray50")))) (font-lock-keyword-face ((t (:foreground "blue")))) (font-lock-string-face ((t (:foreground "purple")))) (font-lock-function-name-face ((t (:foreground "dark green")))) (font-lock-variable-name-face ((t (:foreground "saddle brown")))) (font-lock-type-face ((t (:foreground "teal")))) (font-lock-constant-face ((t (:foreground "dark violet")))))) (current-enabled-themes custom-enabled-themes)) (unwind-protect ;; --- TRY block: The main printing logic --- (progn (message "Applying temporary print theme...") (mapc #'disable-theme current-enabled-themes) (custom-theme-set-faces 'print-theme-temporary print-theme-faces) ;; The printing pipeline itself (which works fine on its own) (let* ((html-buffer (htmlize-buffer)) (html-content (with-current-buffer html-buffer (buffer-string))) (temp-html-file (make-temp-file "emacs-print-" nil ".html")) (temp-pdf-file (make-temp-file "emacs-print-" nil ".pdf")) (chrome-path "/Applications/Google Chrome.app/Contents/MacOS/Google Chrome") (lpr-command (format "lpr -o number-up=2 '%s'" temp-pdf-file))) (kill-buffer html-buffer) (unwind-protect (progn (with-temp-file temp-html-file (insert html-content)) (shell-command (format "'%s' --headless --print-to-pdf='%s' --no-pdf-header-footer 'file://%s'" chrome-path temp-pdf-file temp-html-file)) (shell-command lpr-command)) (when (file-exists-p temp-html-file) (delete-file temp-html-file)) (when (file-exists-p temp-pdf-file) (delete-file temp-pdf-file))) (message "Print job sent."))) ;; --- FINALLY block: Restore the original theme --- (progn (message "Restoring original theme...") ;; Unload the temporary print faces (custom-theme-set-faces 'print-theme-temporary) ;; Re-enable the original themes (mapc #'enable-theme current-enabled-themes)))))

Thank you for your expertise.

(defun print-buffer-as-light-theme () "A command to print the buffer by temporarily applying a minimal light theme." (interactive) (let* ((print-theme-faces `((default ((t (:background "white" :foreground "black")))) (font-lock-comment-face ((t (:foreground "gray50")))) (font-lock-keyword-face ((t (:foreground "blue")))) (font-lock-string-face ((t (:foreground "purple")))) (font-lock-function-name-face ((t (:foreground "dark green")))) (font-lock-variable-name-face ((t (:foreground "saddle brown")))) (font-lock-type-face ((t (:foreground "teal")))) (font-lock-constant-face ((t (:foreground "dark violet")))))) (current-enabled-themes custom-enabled-themes)) (unwind-protect ;; --- TRY block: The main printing logic --- (progn (message "Applying temporary print theme...") (mapc #'disable-theme current-enabled-themes) (custom-theme-set-faces 'print-theme-temporary print-theme-faces) ;; The printing pipeline itself (which works fine on its own) (let* ((html-buffer (htmlize-buffer)) (html-content (with-current-buffer html-buffer (buffer-string))) (temp-html-file (make-temp-file "emacs-print-" nil ".html")) (temp-pdf-file (make-temp-file "emacs-print-" nil ".pdf")) (chrome-path "/Applications/Google Chrome.app/Contents/MacOS/Google Chrome") (lpr-command (format "lpr -o number-up=2 '%s'" temp-pdf-file))) (kill-buffer html-buffer) (unwind-protect (progn (with-temp-file temp-html-file (insert html-content)) (shell-command (format "'%s' --headless --print-to-pdf='%s' --no-pdf-header-footer 'file://%s'" chrome-path temp-pdf-file temp-html-file)) (shell-command lpr-command)) (when (file-exists-p temp-html-file) (delete-file temp-html-file)) (when (file-exists-p temp-pdf-file) (delete-file temp-pdf-file))) (message "Print job sent."))) ;; --- FINALLY block: Restore the original theme --- (progn (message "Restoring original theme...") ;; Unload the temporary print faces (custom-theme-set-faces 'print-theme-temporary) ;; Re-enable the original themes (mapc #'enable-theme current-enabled-themes)))))

Source Link

asked Jun 22 at 15:05

Hajime Fujita

How to temporarily apply a light theme for printing in Emacs Lisp on macOS?

I am trying to create a robust function to print the current buffer from Emacs on macOS (Sonoma+). My goal is to get a printout with:

Syntax highlighting (color).
Correct rendering for Japanese (CJK) characters.
A pure white background (even though I use a dark theme).
2-in-1 page layout.

After many attempts, I've concluded that the most reliable approach is to temporarily switch to a minimal, white-background theme just before printing, and then switch back to my original dark theme after the print job is sent.

My Attempt

I wrote the following function to achieve this. The logic is:

Define a minimal set of faces for a "print theme" with a white background.
Save the user's currently enabled themes.
Use unwind-protect to ensure the original theme is always restored.
In the try block: disable the current theme, apply the temporary print faces using custom-theme-set-faces, and then run my printing pipeline (which uses htmlize and headless Chrome to generate and print a PDF).
In the finally block: unload the temporary print faces and re-enable the user's original themes.

The Problematic Code

Here is the function I tried to implement:

(defun print-buffer-as-light-theme () "A command to print the buffer by temporarily applying a minimal light theme." (interactive) (let* ((print-theme-faces `((default ((t (:background "white" :foreground "black")))) (font-lock-comment-face ((t (:foreground "gray50")))) (font-lock-keyword-face ((t (:foreground "blue")))) (font-lock-string-face ((t (:foreground "purple")))) (font-lock-function-name-face ((t (:foreground "dark green")))) (font-lock-variable-name-face ((t (:foreground "saddle brown")))) (font-lock-type-face ((t (:foreground "teal")))) (font-lock-constant-face ((t (:foreground "dark violet")))))) (current-enabled-themes custom-enabled-themes)) (unwind-protect ;; --- TRY block: The main printing logic --- (progn (message "Applying temporary print theme...") (mapc #'disable-theme current-enabled-themes) (custom-theme-set-faces 'print-theme-temporary print-theme-faces) ;; The printing pipeline itself (which works fine on its own) (let* ((html-buffer (htmlize-buffer)) (html-content (with-current-buffer html-buffer (buffer-string))) (temp-html-file (make-temp-file "emacs-print-" nil ".html")) (temp-pdf-file (make-temp-file "emacs-print-" nil ".pdf")) (chrome-path "/Applications/Google Chrome.app/Contents/MacOS/Google Chrome") (lpr-command (format "lpr -o number-up=2 '%s'" temp-pdf-file))) (kill-buffer html-buffer) (unwind-protect (progn (with-temp-file temp-html-file (insert html-content)) (shell-command (format "'%s' --headless --print-to-pdf='%s' --no-pdf-header-footer 'file://%s'" chrome-path temp-pdf-file temp-html-file)) (shell-command lpr-command)) (when (file-exists-p temp-html-file) (delete-file temp-html-file)) (when (file-exists-p temp-pdf-file) (delete-file temp-pdf-file))) (message "Print job sent."))) ;; --- FINALLY block: Restore the original theme --- (progn (message "Restoring original theme...") ;; Unload the temporary print faces (custom-theme-set-faces 'print-theme-temporary) ;; Re-enable the original themes (mapc #'enable-theme current-enabled-themes)))))

The Error

When I run this function (M-x print-buffer-as-light-theme), it fails with the following error in the minibuffer:

Unknown theme 'print-theme-temporary'

This error seems to be triggered by the (custom-theme-set-faces 'print-theme-temporary) call in the cleanup (finally) block. It appears that applying faces with custom-theme-set-faces does not register a "theme" that can be unloaded by calling the same function with only the theme name.

My Question

Thank you for your expertise.

osx faces