avoid redraw when there's no change

while i was timing the performance issue, i noticed that there was lots
of random redrawing going on.

turns out there were coming from here; if someone presses CTRL/ALT etc
without pressing anything else, nothing will be inserted, so nothing
will change. but the code will `break`, go down and do a needless redraw.

this patch changes it to simply return if the keypress iscntrl()

also avoid potential UB by casting *buf into an unsigned char.

1 files changed, 3 insertions, 2 deletions

diff --git a/dmenu.c b/dmenu.c
index 085dc29..19f6385 100644
--- a/dmenu.c
+++ b/dmenu.c
@@ -415,8 +415,9 @@ keypress(XKeyEvent *ev)
         switch(ksym) {
         default:
 insert:
-                if (!iscntrl(*buf))
-                        insert(buf, len);
+                if (iscntrl((unsigned char)*buf))
+                        return;
+                insert(buf, len);
                 break;
         case XK_Delete:
         case XK_KP_Delete: