From 681bd5096ee416b50dd7338de30af7b3db385a36 Mon Sep 17 00:00:00 2001
From: Nicolas James <nj3ahxac@gmail.com>
Date: Sun, 29 Mar 2026 20:44:23 +1100
Subject: Implement Reflex - break AntiLag in the process. Remove AntiLag1. WIP

---
 src/swapchain_monitor.hh | 69 ++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 69 insertions(+)
 create mode 100644 src/swapchain_monitor.hh

(limited to 'src/swapchain_monitor.hh')

diff --git a/src/swapchain_monitor.hh b/src/swapchain_monitor.hh
new file mode 100644
index 0000000..5678630
--- /dev/null
+++ b/src/swapchain_monitor.hh
@@ -0,0 +1,69 @@
+#ifndef SWAPCHAIN_MONITOR_HH_
+#define SWAPCHAIN_MONITOR_HH_
+
+// The purpose of this file is to provide a SwapchainMonitor class definition.
+
+#include <vulkan/vulkan_core.h>
+
+#include <chrono>
+#include <condition_variable>
+#include <deque>
+#include <mutex>
+#include <thread>
+
+#include "queue_context.hh"
+
+namespace low_latency {
+
+class DeviceContext;
+
+// A swapchain monitor's job is to provide asynchronous wakeups for threads
+// which request low_latency once the previous presentation has completed.
+// It does this by signalling a semaphore a la VK_NV_low_latency2.
+class SwapchainMonitor {
+  private:
+    const DeviceContext& device;
+
+    // Configurarable params for this swapchain.
+    std::chrono::milliseconds present_delay = std::chrono::milliseconds{0};
+    bool was_low_latency_requested = false;
+
+    struct WakeupSemaphore {
+        VkSemaphore timeline_semaphore;
+        std::uint64_t value;
+
+      public:
+        void signal(const DeviceContext& device) const;
+    };
+    std::deque<WakeupSemaphore> wakeup_semaphores;
+    std::deque<QueueContext::submissions_t> in_flight_submissions;
+
+    std::mutex mutex;
+    std::condition_variable_any cv;
+    std::jthread swapchain_worker;
+
+  private:
+    void do_swapchain_monitor(const std::stop_token stoken);
+
+  public:
+    SwapchainMonitor(const DeviceContext& device,
+                     const bool was_low_latency_requested);
+    SwapchainMonitor(const SwapchainMonitor&);
+    SwapchainMonitor(SwapchainMonitor&&);
+    SwapchainMonitor operator=(const SwapchainMonitor&);
+    SwapchainMonitor operator=(SwapchainMonitor&&);
+    ~SwapchainMonitor();
+
+  public:
+    void update_params(const bool was_low_latency_requested,
+                       const std::chrono::milliseconds present_delay);
+
+    void notify_semaphore(const VkSemaphore& timeline_semaphore,
+                          const std::uint64_t& value);
+
+    void notify_present(const QueueContext::submissions_t& submissions);
+};
+
+} // namespace low_latency
+
+#endif
\ No newline at end of file
-- 
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