inputw: improve correctness and startup performance, by NRK

Always use ~30% of the monitor width for the input in horizontal mode.

Patch adapted from NRK patches.
This also does not calculate inputw when using vertical mode anymore (because
the code is removed).

dmenu.c

@@ -610,13 +610,12 @@ static void
 setup(void)
 {
 	int x, y, i, j;
-	unsigned int du, tmp;
+	unsigned int du;
 	XSetWindowAttributes swa;
 	XIM xim;
 	Window w, dw, *dws;
 	XWindowAttributes wa;
 	XClassHint ch = {"dmenu", "dmenu"};
-	struct item *item;
 #ifdef XINERAMA
 	XineramaScreenInfo *info;
 	Window pw;
@@ -674,12 +673,7 @@ setup(void)
 		mw = wa.width;
 	}
 	promptw = (prompt && *prompt) ? TEXTW(prompt) - lrpad / 4 : 0;
-	for (item = items; item && item->text; ++item) {
-		if ((tmp = textw_clamp(item->text, mw/3)) > inputw) {
-			if ((inputw = tmp) == mw/3)
-				break;
-		}
-	}
+	inputw = mw / 3; /* input width: ~30% of monitor width */
 	match();
 
 	/* create menu window */