Make string-pixel-width slightly speedier

* lisp/emacs-lisp/subr-x.el (string-pixel-width): Speed up
string-pixel-width in the zero-length string case.

diff --git a/lisp/emacs-lisp/subr-x.el b/lisp/emacs-lisp/subr-x.el
index 1f69850958c6dc4aaa40533f6a9cc8306786bde2..647397e7f7b37b32dec97b5a9ee8d041cb038d3a 100644 (file)
--- a/lisp/emacs-lisp/subr-x.el
+++ b/lisp/emacs-lisp/subr-x.el
@@ -444,9 +444,11 @@ is inserted before adjusting the number of empty lines."
 ;;;###autoload
 (defun string-pixel-width (string)
   "Return the width of STRING in pixels."
-  (with-temp-buffer
-    (insert string)
-    (car (buffer-text-pixel-size nil nil t))))
+  (if (zerop (length string))
+      0
+    (with-temp-buffer
+      (insert string)
+      (car (buffer-text-pixel-size nil nil t)))))
 
 ;;;###autoload
 (defun string-glyph-split (string)