function to change font size

settings/theme-settings.el

@@ -57,6 +57,19 @@
  ((find-font (font-spec :family "DejaVu Sans Mono"))
   (set-frame-font (font-spec :family "DejaVu Sans Mono"))) )
 
+(defun my-font-set-size (size &optional face)
+  "Change font SIZE of (default) FACE.
+Example:
+- (my-font-set-size 16)
+- (my-font-set-size 14 'default)"
+  (interactive `(,(read-number "Font size: ")))
+  (let ((f (if face face 'default)))
+    (message "%s" f)
+    (set-face-font
+     f
+     (font-spec :family (plist-get (font-face-attributes (face-font f)) :family)
+                :size size)) ))
+
 ;; (Set-fontset-font FONTSET CHARACTERS FONT-SPEC &optional FRAME ADD)
 ;; CHARACTERS see `script-representative-chars' and
 ;; ‘list-character-sets’ and ‘list-charset-chars’ for the list of