Improve speed of drw_text when provided with large strings

Calculates len & ew in drw_font_getexts loop by incrementing instead of
decrementing; as such avoids proportional increase in time spent in loop
based on provided strings size.

drw.c

@@ -310,8 +310,11 @@ drw_text(Drw *drw, int x, int y, unsigned int w, unsigned int h, unsigned int lp
 		if (utf8strlen) {
 			drw_font_getexts(usedfont, utf8str, utf8strlen, &ew, NULL);
 			/* shorten text if necessary */
-			for (len = MIN(utf8strlen, sizeof(buf) - 1); len && ew > w; len--)
-				drw_font_getexts(usedfont, utf8str, len, &ew, NULL);
+			if (ew > w)
+				for (ew = 0, len = 0; ew < w - lpad * 2 && len < MIN(utf8strlen, sizeof(buf) - 1); len++)
+					drw_font_getexts(usedfont, utf8str, len, &ew, NULL);
+			else
+				len = MIN(utf8strlen, sizeof(buf) - 1);
 
 			if (len) {
 				memcpy(buf, utf8str, len);