[idd] elect the fastest frame timing client

idd/LGIdd/CFrameScheduler.h

@@ -0,0 +1,71 @@
+/**
+ * Looking Glass
+ * Copyright © 2017-2026 The Looking Glass Authors
+ * https://looking-glass.io
+ *
+ * This program is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License as published by the Free
+ * Software Foundation; either version 2 of the License, or (at your option)
+ * any later version.
+ *
+ * This program is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for
+ * more details.
+ *
+ * You should have received a copy of the GNU General Public License along
+ * with this program; if not, write to the Free Software Foundation, Inc., 59
+ * Temple Place, Suite 330, Boston, MA 02111-1307 USA
+ */
+
+#pragma once
+
+#include <Windows.h>
+#include <stdint.h>
+
+extern "C" {
+  #include <lgmp/lgmp.h>
+}
+
+#include "common/KVMFR.h"
+
+class CFrameScheduler
+{
+public:
+  struct Schedule
+  {
+    uint32_t clientID;
+    uint32_t generation;
+    uint64_t period;
+    uint64_t targetSlack;
+  };
+
+private:
+  struct Client
+  {
+    uint32_t clientID;
+    uint32_t generation;
+    uint64_t period;
+    uint64_t targetSlack;
+    uint64_t expiry;
+    bool     subscribed;
+    bool     active;
+  };
+
+  mutable SRWLOCK m_lock = SRWLOCK_INIT;
+  Client          m_clients[LGMP_MAX_CLIENTS] = {};
+  Schedule        m_schedule                  = {};
+  bool            m_scheduling                = false;
+
+  Client * FindClient(uint32_t clientID);
+  void ElectOwner(uint64_t now);
+
+public:
+  static uint64_t Nanotime();
+
+  void Reset();
+  void UpdateSubscribers(const uint32_t * clientIDs, unsigned count,
+    uint64_t now);
+  bool UpdateSchedule(const KVMFRFrameSchedule& schedule, uint64_t now);
+  bool GetSchedule(Schedule& schedule) const;
+};