markdown-update-header-faces needed explicit call on startup

User saves customization of `markdown-header-scaling` and restarts
emacs only to find headers do not resize because the `:set` attribute
of `defcustom markdown-header-scaling` is not explicitly called.

Rationalize the defcustom stuff and test.

Author: dickmao

markdown-mode.el

@@ -2039,7 +2039,7 @@ headers of levels one through six respectively."
   :initialize 'custom-initialize-default
   :set (lambda (symbol value)
          (set-default symbol value)
-         (markdown-update-header-faces value))
+         (markdown-update-header-faces))
   :group 'markdown-faces
   :package-version '(markdown-mode . "2.2"))
 
@@ -2051,44 +2051,38 @@ Used when `markdown-header-scaling' is non-nil."
   :initialize 'custom-initialize-default
   :set (lambda (symbol value)
          (set-default symbol value)
-         (markdown-update-header-faces markdown-header-scaling value))
+         (markdown-update-header-faces))
   :group 'markdown-faces)
 
 (defun markdown-make-header-faces ()
   "Build the faces used for Markdown headers."
-  (let ((inherit-faces '(font-lock-function-name-face)))
-    (when markdown-header-scaling
-      (setq inherit-faces (cons 'variable-pitch inherit-faces)))
+  (unless (facep 'markdown-header-face)
     (defface markdown-header-face
-      `((t (:inherit ,inherit-faces :weight bold)))
+      '((t (:inherit (font-lock-function-name-face) :weight bold)))
       "Base face for headers."
-      :group 'markdown-faces))
-  (dotimes (num 6)
-    (let* ((num1 (1+ num))
-           (face-name (intern (format "markdown-header-face-%s" num1)))
-           (scale (if markdown-header-scaling
-                      (float (nth num markdown-header-scaling-values))
-                    1.0)))
-      (eval
-       `(defface ,face-name
-          '((t (:inherit markdown-header-face :height ,scale)))
-          (format "Face for level %s headers.
+      :group 'markdown-faces)
+    (dotimes (num 6)
+      (let* ((num1 (1+ num))
+             (face-name (intern (format "markdown-header-face-%s" num1)))
+             (scale (float (nth num markdown-header-scaling-values))))
+        (eval
+         `(defface ,face-name
+            '((t (:inherit (variable-pitch markdown-header-face) :height ,scale)))
+            (format "Face for level %s headers.
 You probably don't want to customize this face directly. Instead
 you can customize the base face `markdown-header-face' or the
 variable-height variable `markdown-header-scaling'." ,num1)
-          :group 'markdown-faces)))))
+            :group 'markdown-faces))))))
 
-(markdown-make-header-faces)
-
-(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'."
+(defun markdown-update-header-faces (&optional _scaling _scaling-values)
+  "Update header faces using current values of markdown-header-scaling and
+markdown-header-scaling-values.  Arguments are ignored but retained to avoid breakage."
+  (markdown-make-header-faces)
   (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))))))
+           (scale (if markdown-header-scaling
+                      (float (nth num markdown-header-scaling-values))
+                    1.0)))
       (unless (get face-name 'saved-face) ; Don't update customized faces
         (set-face-attribute face-name nil :height scale)))))
 
@@ -9686,6 +9680,7 @@ rows and columns and the column alignment."
     (markdown-live-preview-remove)))
 
 
+(markdown-update-header-faces)
 (provide 'markdown-mode)
 
 ;; Local Variables:

tests/markdown-test.el

@@ -119,6 +119,12 @@ This file is not saved."
   (dolist (loc (number-sequence begin end))
     (message "%d: %s" loc (get-char-property loc prop))))
 
+(defun markdown-test-range-has-face-attribute (begin end plst)
+  "Verify that range BEGIN to END has face containing PROP=VALUE."
+  (dolist (loc (number-sequence begin end))
+    (cl-loop for (k v) on plst by #'cddr
+             do (should (equal (face-attribute (get-char-property loc 'face) k) v)))))
+
 (defun markdown-test-range-has-property (begin end prop value)
   "Verify that range BEGIN to END has PROP equal to or containing VALUE."
   (let (vals fail-loc)
@@ -3083,6 +3089,25 @@ takes precedence)."
     (should (markdown-on-heading-p))
     (should-not (markdown-range-property-any 453 484 'face '(markdown-hr-face)))))
 
+(ert-deftest test-markdown-font-lock/heading-height ()
+  "User customizes scaling, and restarts emacs.  Scaling needs to render."
+  (let ((restore-scaling markdown-header-scaling)
+        (restore-scaling-values markdown-header-scaling-values))
+    (markdown-test-string
+        "# h1
+"
+      (custom-set-variables '(markdown-header-scaling t t))
+      (markdown-test-range-has-face-attribute 3 4
+                            `(:height ,(car markdown-header-scaling-values)))
+      (custom-set-variables '(markdown-header-scaling nil t))
+      (markdown-test-range-has-face-attribute 3 4 '(:height 1.0))
+      (custom-set-variables '(markdown-header-scaling t t)
+                            '(markdown-header-scaling-values
+                              `(3.0 ,(cdr markdown-header-scaling-values))))
+      (markdown-test-range-has-face-attribute 3 4 '(:height 3.0))
+      (custom-set-variables '(markdown-header-scaling restore-scaling t)
+                            '(markdown-header-scaling-values restore-scaling-values t)))))
+
 (ert-deftest test-markdown-font-lock/heading-code-block-no-whitespace ()
   "Headings immediately before code blocks should be identified correctly.
 See GH-234."