fix: signal a lock screen only once it handles the signal

src/agent/lockers.h

@@ -0,0 +1,22 @@
+// SPDX-License-Identifier: GPL-3.0-or-later
+//
+// The lock screens that are programs of their own and take signals from
+// outside: hyprlock and swaylock open on SIGUSR1.
+
+#pragma once
+
+#include <QByteArray>
+#include <QList>
+
+#include <sys/types.h>
+
+namespace Lockers
+{
+// The ones of this user on this display, or only those called name.
+QList<pid_t> find(const QByteArray &name = {});
+// Sends sig to each that is ready for it, and says how many were not. A
+// lock screen only handles its signals once the screen is locked: before
+// that, the signal kills it, and the compositor keeps the screen locked with
+// nobody to open it.
+int signal(int sig, const QByteArray &name = {});
+}