Add targetFrameTime option for Vulkan backend

lib/graphicsdev/Common.cpp

@@ -1,5 +1,8 @@
 #include "Common.hpp"
+
 #include <cmath>
+#include <numeric>
+#include <thread>
 
 namespace boo {
 
@@ -12,4 +15,25 @@ void UpdateGammaLUT(ITextureD* tex, float gamma) {
   tex->unmap();
 }
 
+void Limiter::Sleep(nanotime_t targetFrameTime) {
+  if (targetFrameTime == 0) {
+    return;
+  }
+
+  auto start = delta_clock::now();
+  nanotime_t sleepTime = targetFrameTime - TimeSince(m_oldTime);
+  m_overhead = std::accumulate(m_overheadTimes.begin(), m_overheadTimes.end(), nanotime_t{}) /
+               static_cast<nanotime_t>(m_overheadTimes.size());
+  if (sleepTime > m_overhead) {
+    nanotime_t adjustedSleepTime = sleepTime - m_overhead;
+    std::this_thread::sleep_for(std::chrono::nanoseconds(adjustedSleepTime));
+    nanotime_t overslept = TimeSince(start) - adjustedSleepTime;
+    if (overslept < targetFrameTime) {
+      m_overheadTimes[m_overheadTimeIdx] = overslept;
+      m_overheadTimeIdx = (m_overheadTimeIdx + 1) % m_overheadTimes.size();
+    }
+  }
+  m_oldTime = delta_clock::now();
+}
+
 } // namespace boo

lib/graphicsdev/Common.hpp

@@ -7,6 +7,7 @@
 #include <atomic>
 #include <cassert>
 #include <condition_variable>
+#include <chrono>
 #include <mutex>
 #include <queue>
 #include <thread>
@@ -283,4 +284,22 @@ public:
 #define SCOPED_GRAPHICS_DEBUG_GROUP(...)
 #endif
 
+class Limiter {
+  using delta_clock = std::chrono::steady_clock;
+  using nanotime_t = std::chrono::nanoseconds::rep;
+
+public:
+  void Sleep(nanotime_t targetFrameTimeNs);
+
+private:
+  delta_clock::time_point m_oldTime;
+  std::array<nanotime_t, 4> m_overheadTimes{};
+  size_t m_overheadTimeIdx = 0;
+  nanotime_t m_overhead = 0;
+
+  nanotime_t TimeSince(delta_clock::time_point start) {
+    return std::chrono::duration_cast<std::chrono::nanoseconds>(delta_clock::now() - start).count();
+  }
+};
+
 } // namespace boo

lib/graphicsdev/Vulkan.cpp

@@ -2871,6 +2871,8 @@ struct VulkanCommandQueue final : IGraphicsCommandQueue {
 
   std::vector<boo::ObjToken<boo::IObj>> m_drawResTokens[2];
 
+  Limiter m_frameLimiter;
+
   void resetCommandBuffer() {
     ThrowIfFailed(vk::ResetCommandBuffer(m_cmdBufs[m_fillBuf], 0));
     VkCommandBufferBeginInfo cmdBufBeginInfo = {};
@@ -4076,6 +4078,7 @@ void VulkanCommandQueue::execute() {
     present.pResults = nullptr;
 
     ThrowIfFailed(vk::QueuePresentKHR(m_ctx->m_queue, &present));
+    m_frameLimiter.Sleep(m_ctx->m_targetFrameTime);
   }
 
   resetCommandBuffer();