FullscreenUI: Fix incorrect vsync state on unpause

src/core/system.cpp

@@ -2192,11 +2192,10 @@ void System::UpdateSpeedLimiterState()
     }
   }
 
-  const bool is_non_standard_speed = (std::abs(target_speed - 1.0f) > 0.05f);
+  const bool is_non_standard_speed = IsRunningAtNonStandardSpeed();
   const bool audio_sync_enabled =
     !IsRunning() || (m_throttler_enabled && g_settings.audio_sync_enabled && !is_non_standard_speed);
-  const bool video_sync_enabled =
-    !IsRunning() || (m_throttler_enabled && g_settings.video_sync_enabled && !is_non_standard_speed);
+  const bool video_sync_enabled = ShouldUseVSync();
   const float max_display_fps = (!IsRunning() || m_throttler_enabled) ? 0.0f : g_settings.display_max_fps;
   Log_InfoPrintf("Target speed: %f%%", target_speed * 100.0f);
   Log_InfoPrintf("Syncing to %s%s", audio_sync_enabled ? "audio" : "",
@@ -2241,6 +2240,11 @@ void System::UpdateSpeedLimiterState()
   }
 }
 
+bool System::ShouldUseVSync()
+{
+  return (!IsRunning() || (m_throttler_enabled && g_settings.video_sync_enabled && !IsRunningAtNonStandardSpeed()));
+}
+
 bool System::IsFastForwardEnabled()
 {
   return m_fast_forward_enabled;

src/core/system.h

@@ -400,6 +400,9 @@ void ToggleWidescreen();
 /// Returns true if fast forwarding or slow motion is currently active.
 bool IsRunningAtNonStandardSpeed();
 
+/// Returns true if vsync should be used.
+bool ShouldUseVSync();
+
 /// Quick switch between software and hardware rendering.
 void ToggleSoftwareRendering();
 

src/duckstation-qt/qthost.cpp

@@ -870,12 +870,18 @@ bool EmuThread::acquireHostDisplay(HostDisplay::RenderAPI api)
 
   m_is_exclusive_fullscreen = g_host_display->IsFullscreen();
 
-  if (m_run_fullscreen_ui && !FullscreenUI::Initialize())
+  if (m_run_fullscreen_ui)
   {
-    Log_ErrorPrint("Failed to initialize fullscreen UI");
-    releaseHostDisplay();
-    m_run_fullscreen_ui = false;
-    return false;
+    if (!FullscreenUI::Initialize())
+    {
+      Log_ErrorPrint("Failed to initialize fullscreen UI");
+      releaseHostDisplay();
+      m_run_fullscreen_ui = false;
+      return false;
+    }
+
+    // start with vsync on
+    g_host_display->SetVSync(true);
   }
 
   return true;

src/frontend-common/fullscreen_ui.cpp

@@ -166,7 +166,6 @@ static std::string TimeToPrintableString(time_t t);
 //////////////////////////////////////////////////////////////////////////
 // Main
 //////////////////////////////////////////////////////////////////////////
-static void UpdateForcedVsync(bool should_force);
 static void PauseForMenuOpen();
 static void ClosePauseMenu();
 static void OpenPauseSubMenu(PauseSubMenu submenu);
@@ -440,10 +439,6 @@ bool FullscreenUI::Initialize()
   if (!System::IsValid())
     SwitchToLanding();
 
-  // force vsync on so we don't run at thousands of fps
-  // Initialize is called on the GS thread, so we can access the display directly.
-  UpdateForcedVsync(System::GetState() != System::State::Running);
-
   return true;
 }
 
@@ -458,13 +453,6 @@ bool FullscreenUI::HasActiveWindow()
                            ImGuiFullscreen::IsChoiceDialogOpen() || ImGuiFullscreen::IsFileSelectorOpen());
 }
 
-void FullscreenUI::UpdateForcedVsync(bool should_force)
-{
-  // force vsync on so we don't run at thousands of fps
-  // toss it through regardless of the mode, because options can change it
-  g_host_display->SetVSync((should_force && !g_settings.video_sync_enabled) ? true : false);
-}
-
 void FullscreenUI::OnSystemStarted()
 {
   if (!IsInitialized())
@@ -479,7 +467,7 @@ void FullscreenUI::OnSystemPaused()
   if (!IsInitialized())
     return;
 
-  UpdateForcedVsync(true);
+  g_host_display->SetVSync(true);
 }
 
 void FullscreenUI::OnSystemResumed()
@@ -487,7 +475,7 @@ void FullscreenUI::OnSystemResumed()
   if (!IsInitialized())
     return;
 
-  UpdateForcedVsync(false);
+  g_host_display->SetVSync(System::ShouldUseVSync());
 }
 
 void FullscreenUI::OnSystemDestroyed()
@@ -495,9 +483,9 @@ void FullscreenUI::OnSystemDestroyed()
   if (!IsInitialized())
     return;
 
+  g_host_display->SetVSync(true);
   s_pause_menu_was_open = false;
   SwitchToLanding();
-  UpdateForcedVsync(true);
 }
 
 void FullscreenUI::OnRunningGameChanged()