Fix org-mu4e-compose font locking

elisp/org-mu4e-compose.el

@@ -80,6 +80,22 @@ about this change."
           (setq end (match-beginning 0)))
         (cons (1+ start) end)))))
 
+(defun org-mu4e--make-face-font-lock-face (start end)
+  "Copy the value of all `face' text properties to `font-lock-face'.
+The affected area is START to END in the current buffer."
+  (with-restriction start end
+    (cl-do ((pos (point-min) (next-property-change pos))
+            (begin (point-min))
+            (face (or (get-text-property (point) 'face)
+                      'default)))
+        ((not pos) (put-text-property begin (point-max) 'font-lock-face face))
+      (let ((new-face (or (get-text-property pos 'face)
+                          'default)))
+        (unless (equal face new-face)
+          (put-text-property begin pos 'font-lock-face face)
+          (setq face new-face
+                begin pos))))))
+
 (defun org-mu4e--pretty-print-fontify-html-part ()
   "Pretty print and fontify the HTML part of the current buffer."
   (when-let* ((bounds (org-mu4e--bounds-of-mime-part "text/html"))
@@ -97,6 +113,7 @@ about this change."
                  (indent-region (point-min) (point-max)))
                (put-text-property (point-min) (point-max) 'fontified nil)
                (font-lock-ensure)
+               (org-mu4e--make-face-font-lock-face (point-min) (point-max))
                (buffer-string))))
         (delete-region (car bounds) (cdr bounds))
         (goto-char (car bounds))
@@ -113,7 +130,7 @@ about this change."
                                           after-change-functions)))
         (delete-region (point-min) (point-max))
         (insert ascii-content)
-        (set-text-properties (point-min) (point-max) '(:fontified t))))))
+        (put-text-property (point-min) (point-max) 'font-lock-face 'default)))))
 
 (defun org-mu4e--htmlize-and-cleanup ()
   "HTMLize and cleanup the visible portion of the buffer.