Title: Improved Modifier Handling
Author: Eric Pruitt (https://www.codevat.com/, https://github.com/ericpruitt/)

With this patch, modifier keys only cause the screen to display the failure
color when they are released without pressing a complementary key.

This patch depends on "slock-00-pam-authentication.diff".

--- a/slock.c
+++ b/slock.c
@@ -226,6 +226,7 @@ readpw(struct xrandr *rr, int nscreens, const char *hash)
 	unsigned int len, color;
 	KeySym ksym;
 	XEvent ev;
+	int seenkeypress = 0;
 
 	len = 0;
 	running = 1;
@@ -233,9 +234,14 @@ readpw(struct xrandr *rr, int nscreens, const char *hash)
 	 * utility. This way the user can easily set a customized DPMS
 	 * timeout. */
 	while (running && !XNextEvent(dpy, &ev)) {
-		if (ev.type == KeyPress) {
+		if (ev.type == KeyPress || ev.type == KeyRelease) {
 			explicit_bzero(&buf, sizeof(buf));
 			num = XLookupString(&ev.xkey, buf, sizeof(buf), &ksym, 0);
+			seenkeypress |= ev.type == KeyPress;
+			if ((ev.type == KeyRelease && (num || !seenkeypress)) ||
+				(ev.type == KeyPress && !num)) {
+				continue;
+			}
 			if (IsKeypadKey(ksym)) {
 				if (ksym == XK_KP_Enter)
 					ksym = XK_Return;