Enable different header scaling in markdown-mode and markdown-view-mode

[mattiasb]

Expected Behavior

I would like to have header scaling enabled in markdown-view-mode but
not in markdown-mode.

I have a local hack in my personal config that looks like this:

;;;###autoload
(define-minor-mode +markdown-scale-headers-mode
  "Scale `markdown-mode' headers."
  :lighter "M↑"
  (+markdown-update-header-faces +markdown-scale-headers-mode))

(defun +markdown-update-header-faces (&optional scaling scaling-values)
  "Update header faces, depending on if header SCALING is desired.
If so, use given list of SCALING-VALUES relative to the baseline
size of `markdown-header-face'.
Like `markdown-update-header-faces' but buffer local."
  (dotimes (num 6)
    (let* ((face-name (intern (format "markdown-header-face-%s" (1+ num))))
           (scale (cond ((not scaling) 1.0)
                        (scaling-values (float (nth num scaling-values)))
                        (t (float (nth num markdown-header-scaling-values))))))
      (unless (get face-name 'saved-face) ; Don't update customized faces
        (face-remap-add-relative face-name :height scale)))))

The important points in the code snippet above are:

1. I add a buffer local minor mode for enabling or disabling header scaling
2. I change markdown-update-header-faces like this:

   - (set-face-attribute face-name nil :height scale)
   + (face-remap-add-relative face-name :height scale)

Posting this hack in the issue itself is mostly to show that it can be done
but I realize there are several ways to do this and there might be downsides
I haven't considered.

Actual Behavior

Enabling markdown-header-scaling will toggle header scaling in all modes.

Steps to Reproduce

1. Enable header scaling

Software Versions

• Markdown Mode: 6f59f72 + these patches:
  • Mark markdown-css-paths safe as a file local var #856
  • Support relative paths in stylesheets #857
• Emacs: 29.4
• OS: Fedora Workstation 41