refactor(core): implement high-precision FPS limiter

Replace scattered frame rate limiting logic with centralized `FPSLimiter` class.

**Key improvements:**
- High-precision timing using `RDTSC`, `QueryPerformanceFrequency`, and waitable timers
- Unified FPS limit handling from server, client scripts, user settings, and VSync
- Dynamic CEF browser frame rate synchronization
- Consistent frame pacing through `CModManager` pulse integration

**Changes:**
- Add `FPSLimiter` class with centralized frame limiting logic
- Integrate limiter into `CCore`, replacing old methods and variables
- Refactor `CCommands` to handle `fps_limit` and `vsync` cvars
- Update all APIs, Lua functions, and network packets to use `FPSLimiterInterface`

Author: PerikiyoXD

Client/cefweb/CWebCore.cpp

@@ -479,6 +479,14 @@ void CWebCore::OnPostScreenshot()
     }
 }
 
+void CWebCore::OnFPSLimitChange(int iFPS)
+{
+    for (auto& pWebView : m_WebViews)
+    {
+        pWebView->GetCefBrowser()->GetHost()->SetWindowlessFrameRate(iFPS);
+    }
+}
+
 void CWebCore::ProcessInputMessage(UINT uMsg, WPARAM wParam, LPARAM lParam)
 {
     if (!m_pFocusedWebView ||

Client/cefweb/CWebCore.h

@@ -96,6 +96,8 @@ class CWebCore : public CWebCoreInterface
     void OnPreScreenshot();
     void OnPostScreenshot();
 
+    void OnFPSLimitChange(int newFPS);
+
     bool SetGlobalAudioVolume(float fVolume);
 
     bool        UpdateListsFromMaster();

Client/cefweb/CWebView.cpp

@@ -54,7 +54,7 @@ void CWebView::Initialise()
 {
     // Initialise the web session (which holds the actual settings) in in-memory mode
     CefBrowserSettings browserSettings;
-    browserSettings.windowless_frame_rate = g_pCore->GetFrameRateLimit();
+    browserSettings.windowless_frame_rate = g_pCore->GetFPSLimiter()->GetFPSTarget();
     browserSettings.javascript_access_clipboard = cef_state_t::STATE_DISABLED;
     browserSettings.javascript_dom_paste = cef_state_t::STATE_DISABLED;
     browserSettings.webgl = cef_state_t::STATE_ENABLED;

Client/core/CClientVariables.cpp

@@ -10,6 +10,7 @@
  *****************************************************************************/
 
 #include "StdInc.h"
+// #include "FPSLimiter.h"
 
 template <>
 CClientVariables* CSingleton<CClientVariables>::m_pSingleton = NULL;
@@ -234,7 +235,20 @@ void CClientVariables::ValidateValues()
 
     ClampValue("console_pos", CVector2D(0, 0), CVector2D(uiViewportWidth - 32, uiViewportHeight - 32));
     ClampValue("console_size", CVector2D(50, 50), CVector2D(uiViewportWidth - 32, uiViewportHeight - 32));
-    ClampValue("fps_limit", 0, std::numeric_limits<short>::max());
+
+    // fps_limit is either 0 (no limit) or valid clamp range FPS_LIMIT_MIN, FPS_LIMIT_MAX so this won't work:
+    // ClampValue("fps_limit", 0, std::numeric_limits<short>::max());
+    // So do it with our specialized FPS validation function
+    {
+        // Re-validate fps_limit cvar to ensure it's within valid range
+        // This is to catch users manually editing the config file with invalid values
+        // We don't clamp it here as we want to allow 0 (unlimited)
+        uint uiTemp;
+        CVARS_GET("fps_limit", uiTemp);
+        uiTemp = FPSLimiter::ValidateFPS(uiTemp);
+        CVARS_SET("fps_limit", uiTemp);
+    }
+
     ClampValue("chat_font", 0, 3);
     ClampValue("chat_lines", 3, 62);
     ClampValue("chat_color", CColor(0, 0, 0, 0), CColor(255, 255, 255, 255));
@@ -261,9 +275,10 @@ void CClientVariables::ValidateValues()
 
 void CClientVariables::LoadDefaults()
 {
-    #define DEFAULT(__x,__y)    if(!Exists(__x)) \
-                                Set(__x,__y)
-    #define _S(__x)             std::string(__x)
+#define DEFAULT(__x, __y) \
+    if (!Exists(__x)) \
+    Set(__x, __y)
+#define _S(__x) std::string(__x)
 
     if (!Exists("nick"))
     {
@@ -279,6 +294,7 @@ void CClientVariables::LoadDefaults()
     DEFAULT("console_size", CVector2D(200, 200));                        // console size
     DEFAULT("serverbrowser_size", CVector2D(720.0f, 495.0f));            // serverbrowser size
     DEFAULT("fps_limit", 100);                                           // frame limiter
+    DEFAULT("vsync", true);                                              // vsync
     DEFAULT("chat_font", 2);                                             // chatbox font type
     DEFAULT("chat_lines", 10);                                           // chatbox lines
     DEFAULT("chat_color", CColor(0, 0, 0, 0));                           // chatbox background color
@@ -379,4 +395,11 @@ void CClientVariables::LoadDefaults()
 #if 0
     DEFAULT ( "streaming_memory",           50 );                           // Streaming memory
 #endif
+
+#undef DEFAULT
+#undef _S
+
+    ValidateValues();            // Paranoid validation of all cvar values
+
+    m_bLoaded = true;            // We have loaded at least the defaults
 }

Client/core/CClientVariables.h

@@ -28,8 +28,9 @@
 class CClientVariables : public CCVarsInterface, public CSingleton<CClientVariables>
 {
     // Sanity macros   << Who ever did this is idiot
-    #define SAN     if(!m_pStorage) return
-    #define SANGET  if(!Node(strVariable)) return false
+    // TODO: (pxd) Remove these macros and ODR violations
+    #define SAN     if(!m_pStorage) { OutputDebugLine("CClientVariables::Get: m_pStorage is NULL"); return; }
+    #define SANGET  if(!Node(strVariable)) { OutputDebugLine(SString("CClientVariables::Get: Node for cvar %s is NULL"), strVariable.c_str()); return false; }
 
 public:
     CClientVariables();
@@ -119,15 +120,15 @@ class CClientVariables : public CCVarsInterface, public CSingleton<CClientVariab
     bool Exists(const std::string& strVariable);
 
     bool Load();
-    bool IsLoaded() { return m_bLoaded; }
+    bool IsLoaded() { return m_bLoaded; }            // TODO: (pxd) Remove if unused? Seems unused
     int  GetRevision() { return m_iRevision; }
     void ValidateValues();
 
 private:
     CXMLNode* Node(const std::string& strVariable);
     void      LoadDefaults();
 
-    bool      m_bLoaded;
+    bool      m_bLoaded;            // TODO: (pxd) Remove if unused? Seems unused
     CXMLNode* m_pStorage;
     int       m_iRevision;
 };