* lisp/frame.el (display-planes): Use logb over truncate + log

Suggested by Basil L. Contovounesios:
https://lists.gnu.org/archive/html/bug-gnu-emacs/2019-03/msg01052.html

diff --git a/lisp/frame.el b/lisp/frame.el
index aa14e87d7b8cb51b53dbb247392707c991d695e4..b39891cd14269847cb1819c1cbae4d2771340947 100644 (file)
--- a/lisp/frame.el
+++ b/lisp/frame.el
@@ -2093,7 +2093,7 @@ If DISPLAY is omitted or nil, it defaults to the selected frame's display."
      ((eq frame-type 'pc)
       4)
      (t
-      (truncate (log (length (tty-color-alist)) 2))))))
+      (logb (length (tty-color-alist)))))))
 
 (declare-function x-display-color-cells "xfns.c" (&optional terminal))