HostInterface: Implement non-vsync based speed throttler

Needed for PAL games.

src/core/host_interface.cpp

@@ -1,6 +1,7 @@
 #include "host_interface.h"
 #include "YBaseLib/ByteStream.h"
 #include "YBaseLib/Log.h"
+#include "YBaseLib/Timer.h"
 #include "bios.h"
 #include "common/audio_stream.h"
 #include "host_display.h"
@@ -8,9 +9,16 @@
 #include <filesystem>
 Log_SetChannel(HostInterface);
 
+#ifdef _WIN32
+#include "YBaseLib/Windows/WindowsHeaders.h"
+#else
+#include <time.h>
+#endif
+
 HostInterface::HostInterface()
 {
   m_settings.SetDefaults();
+  m_last_throttle_time = Y_TimerGetValue();
 }
 
 HostInterface::~HostInterface() = default;
@@ -22,7 +30,7 @@ bool HostInterface::CreateSystem()
   // Pull in any invalid settings which have been reset.
   m_settings = m_system->GetSettings();
   m_paused = true;
-  UpdateAudioVisualSync();
+  UpdateSpeedLimiterState();
   return true;
 }
 
@@ -33,7 +41,7 @@ bool HostInterface::BootSystem(const char* filename, const char* state_filename)
 
   m_paused = m_settings.start_paused;
   ConnectControllers();
-  UpdateAudioVisualSync();
+  UpdateSpeedLimiterState();
   return true;
 }
 
@@ -41,7 +49,7 @@ void HostInterface::DestroySystem()
 {
   m_system.reset();
   m_paused = false;
-  UpdateAudioVisualSync();
+  UpdateSpeedLimiterState();
 }
 
 void HostInterface::ReportError(const char* message)
@@ -110,6 +118,44 @@ std::optional<std::vector<u8>> HostInterface::GetBIOSImage(ConsoleRegion region)
 
 void HostInterface::ConnectControllers() {}
 
+void HostInterface::Throttle()
+{
+  // Allow variance of up to 40ms either way.
+  constexpr s64 MAX_VARIANCE_TIME = INT64_C(40000000);
+
+  // Don't sleep for <1ms or >=period.
+  constexpr s64 MINIMUM_SLEEP_TIME = INT64_C(1000000);
+
+  // Use unsigned for defined overflow/wrap-around.
+  const u64 time = static_cast<u64>(m_throttle_timer.GetTimeNanoseconds());
+  const s64 sleep_time = static_cast<s64>(m_last_throttle_time - time);
+  if (std::abs(sleep_time) >= MAX_VARIANCE_TIME)
+  {
+#ifdef Y_BUILD_CONFIG_RELEASE
+    // Don't display the slow messages in debug, it'll always be slow...
+    // Limit how often the messages are displayed.
+    if (m_speed_lost_time_timestamp.GetTimeSeconds() >= 1.0f)
+    {
+      Log_WarningPrintf("System too %s, lost %.2f ms", sleep_time < 0 ? "slow" : "fast",
+                        static_cast<double>(std::abs(sleep_time) - MAX_VARIANCE_TIME) / 1000000.0);
+      m_speed_lost_time_timestamp.Reset();
+    }
+#endif
+    m_last_throttle_time = time - MAX_VARIANCE_TIME;
+  }
+  else if (sleep_time >= MINIMUM_SLEEP_TIME && sleep_time <= m_throttle_period)
+  {
+#ifdef WIN32
+    Sleep(static_cast<u32>(sleep_time / 1000000));
+#else
+    const struct timespec ts = {0, static_cast<long>(sleep_time)};
+    nanosleep(&ts, nullptr);
+#endif
+  }
+
+  m_last_throttle_time += m_throttle_period;
+}
+
 bool HostInterface::LoadState(const char* filename)
 {
   ByteStream* stream;
@@ -156,13 +202,14 @@ bool HostInterface::SaveState(const char* filename)
   return result;
 }
 
-void HostInterface::UpdateAudioVisualSync()
+void HostInterface::UpdateSpeedLimiterState()
 {
-  const bool speed_limiter_enabled = m_settings.speed_limiter_enabled && !m_speed_limiter_temp_disabled;
-  const bool audio_sync_enabled = speed_limiter_enabled;
-  const bool vsync_enabled = !m_system || m_paused || (speed_limiter_enabled && m_settings.gpu_vsync);
+  m_speed_limiter_enabled = m_settings.speed_limiter_enabled && !m_speed_limiter_temp_disabled;
+
+  const bool audio_sync_enabled = m_speed_limiter_enabled;
+  const bool vsync_enabled = !m_system || m_paused || (m_speed_limiter_enabled && m_settings.gpu_vsync);
   Log_InfoPrintf("Syncing to %s%s", audio_sync_enabled ? "audio" : "",
-                 (speed_limiter_enabled && vsync_enabled) ? " and video" : "");
+                 (m_speed_limiter_enabled && vsync_enabled) ? " and video" : "");
 
   m_audio_stream->SetSync(false);
   m_display->SetVSync(vsync_enabled);

src/core/host_interface.h

@@ -1,6 +1,8 @@
 #pragma once
-#include "types.h"
+#include "YBaseLib/Timer.h"
 #include "settings.h"
+#include "types.h"
+#include <chrono>
 #include <memory>
 #include <optional>
 #include <vector>
@@ -25,6 +27,9 @@ public:
   /// Returns a settings object which can be modified.
   Settings& GetSettings() { return m_settings; }
 
+  /// Adjusts the throttle frequency, i.e. how many times we should sleep per second.
+  void SetThrottleFrequency(double frequency) { m_throttle_period = static_cast<s64>(1000000000.0 / frequency); }
+
   bool CreateSystem();
   bool BootSystem(const char* filename, const char* state_filename);
   void DestroySystem();
@@ -42,16 +47,27 @@ public:
   bool SaveState(const char* filename);
 
 protected:
+  using ThrottleClock = std::chrono::steady_clock;
+
   /// Connects controllers. TODO: Clean this up later...
   virtual void ConnectControllers();
 
-  void UpdateAudioVisualSync();
+  /// Throttles the system, i.e. sleeps until it's time to execute the next frame.
+  void Throttle();
+
+  void UpdateSpeedLimiterState();
 
   std::unique_ptr<HostDisplay> m_display;
   std::unique_ptr<AudioStream> m_audio_stream;
   std::unique_ptr<System> m_system;
   Settings m_settings;
 
+  u64 m_last_throttle_time = 0;
+  s64 m_throttle_period = INT64_C(1000000000) / 60;
+  Timer m_throttle_timer;
+  Timer m_speed_lost_time_timestamp;
+
   bool m_paused = false;
   bool m_speed_limiter_temp_disabled = false;
+  bool m_speed_limiter_enabled = false;
 };

src/duckstation/sdl_host_interface.cpp

@@ -197,6 +197,7 @@ std::unique_ptr<SDLHostInterface> SDLHostInterface::Create(const char* filename
 
   ImGui::NewFrame();
 
+  intf->UpdateSpeedLimiterState();
   intf->OpenGameControllers();
 
   const bool boot = (filename != nullptr || exp1_filename != nullptr || save_state_filename != nullptr);
@@ -209,8 +210,6 @@ std::unique_ptr<SDLHostInterface> SDLHostInterface::Create(const char* filename
       intf->LoadState(save_state_filename);
   }
 
-  intf->UpdateAudioVisualSync();
-
   intf->UpdateFullscreen();
 
   return intf;
@@ -497,7 +496,7 @@ void SDLHostInterface::HandleSDLKeyEvent(const SDL_Event* event)
       if (!repeat)
       {
         m_speed_limiter_temp_disabled = pressed;
-        UpdateAudioVisualSync();
+        UpdateSpeedLimiterState();
       }
     }
     break;
@@ -521,7 +520,7 @@ void SDLHostInterface::HandleSDLKeyEvent(const SDL_Event* event)
       if (pressed && !repeat && m_system)
       {
         m_settings.speed_limiter_enabled = !m_settings.speed_limiter_enabled;
-        UpdateAudioVisualSync();
+        UpdateSpeedLimiterState();
         AddOSDMessage(m_system->GetSettings().speed_limiter_enabled ? "Speed limiter enabled." :
                                                                       "Speed limiter disabled.");
       }
@@ -720,7 +719,7 @@ void SDLHostInterface::DrawQuickSettingsMenu()
   if (ImGui::MenuItem("Enable Speed Limiter", nullptr, &m_settings.speed_limiter_enabled))
   {
     settings_changed = true;
-    UpdateAudioVisualSync();
+    UpdateSpeedLimiterState();
   }
 
   ImGui::Separator();
@@ -749,7 +748,7 @@ void SDLHostInterface::DrawQuickSettingsMenu()
   if (ImGui::MenuItem("VSync", nullptr, &m_settings.gpu_vsync))
   {
     settings_changed = true;
-    UpdateAudioVisualSync();
+    UpdateSpeedLimiterState();
   }
 
   ImGui::Separator();
@@ -1008,7 +1007,7 @@ void SDLHostInterface::DrawSettingsWindow()
 
         if (ImGui::Checkbox("VSync", &m_settings.gpu_vsync))
         {
-          UpdateAudioVisualSync();
+          UpdateSpeedLimiterState();
           settings_changed = true;
         }
         if (ImGui::Checkbox("Linear Filtering", &m_settings.display_linear_filtering))
@@ -1398,7 +1397,12 @@ void SDLHostInterface::Run()
       ImGui::NewFrame();
 
       if (m_system)
+      {
         m_system->GetGPU()->RestoreGraphicsAPIState();
+
+        if (m_speed_limiter_enabled)
+          Throttle();
+      }
     }
 
     if (m_system)
@@ -1426,10 +1430,7 @@ void SDLHostInterface::Run()
   if (m_system)
   {
     if (!SaveState(RESUME_SAVESTATE_FILENAME))
-    {
-      SDL_ShowSimpleMessageBox(SDL_MESSAGEBOX_WARNING, "Save state failed",
-                               "Saving state failed, you will not be able to resume this session.", m_window);
-    }
+      ReportError("Saving state failed, you will not be able to resume this session.");
 
     DestroySystem();
   }