Fix OnStartRecording and OnStopRecording forwards on linux

CHLTVServer::StartRecording is called directly in tv_record on linux,
ignoring the vtable.
Add a detour on linux for these two functions, so we always notice when
recording starts.
Windows actually always uses the vtable to get the function address, so
we don't need to detour anything on windows.

forwards.cpp

@@ -35,12 +35,15 @@
 
 CForwardManager g_pSTVForwards;
 
+// Only windows always uses the vtable for these. Linux does direct calls, so we use detours there.
+#ifdef WIN32
 SH_DECL_HOOK2_void(IDemoRecorder, StartRecording, SH_NOATTRIB, 0, const char *, bool)
 #if SOURCE_ENGINE == SE_CSGO
 SH_DECL_HOOK1_void(IDemoRecorder, StopRecording, SH_NOATTRIB, 0, CGameInfo const *)
 #else
 SH_DECL_HOOK0_void(IDemoRecorder, StopRecording, SH_NOATTRIB, 0)
-#endif
+#endif // SOURCE_ENGINE == SE_CSGO
+#endif // !WIN32
 
 #if SOURCE_ENGINE == SE_CSGO
 SH_DECL_MANUALHOOK13(CHLTVServer_ConnectClient, 0, 0, 0, IClient *, const netadr_t &, int, int, int, const char *, const char *, const char *, int, CUtlVector<NetMsg_SplitPlayerConnect *> &, bool, CrossPlayPlatform_t, const unsigned char *, int);
@@ -126,14 +129,18 @@ void CForwardManager::Shutdown()
 
 void CForwardManager::HookRecorder(IDemoRecorder *recorder)
 {
+#ifdef WIN32
 	SH_ADD_HOOK(IDemoRecorder, StartRecording, recorder, SH_MEMBER(this, &CForwardManager::OnStartRecording_Post), true);
 	SH_ADD_HOOK(IDemoRecorder, StopRecording, recorder, SH_MEMBER(this, &CForwardManager::OnStopRecording_Post), true);
+#endif
 }
 
 void CForwardManager::UnhookRecorder(IDemoRecorder *recorder)
 {
+#ifdef WIN32
 	SH_REMOVE_HOOK(IDemoRecorder, StartRecording, recorder, SH_MEMBER(this, &CForwardManager::OnStartRecording_Post), true);
 	SH_REMOVE_HOOK(IDemoRecorder, StopRecording, recorder, SH_MEMBER(this, &CForwardManager::OnStopRecording_Post), true);
+#endif
 }
 
 void CForwardManager::HookServer(HLTVServerWrapper *wrapper)
@@ -367,21 +374,12 @@ void CForwardManager::OnSpectatorPutInServer()
 	RETURN_META(MRES_IGNORED);
 }
 
+
+// These two hooks are actually only hooked on windows.
 void CForwardManager::OnStartRecording_Post(const char *filename, bool bContinuously)
 {
-	if (m_StartRecordingFwd->GetFunctionCount() == 0)
-		RETURN_META(MRES_IGNORED);
-
 	IDemoRecorder *recorder = META_IFACEPTR(IDemoRecorder);
-	HLTVServerWrapper *wrapper = g_HLTVServers.GetWrapper(recorder);
-	int instance = -1;
-	if (wrapper)
-		instance = wrapper->GetInstanceNumber();
-
-	m_StartRecordingFwd->PushCell(instance);
-	m_StartRecordingFwd->PushString(filename);
-	m_StartRecordingFwd->Execute();
-
+	CallOnStartRecording(recorder, filename, bContinuously);
 	RETURN_META(MRES_IGNORED);
 }
 
@@ -391,12 +389,33 @@ void CForwardManager::OnStopRecording_Post(CGameInfo const *info)
 void CForwardManager::OnStopRecording_Post()
 #endif
 {
-	if (m_StopRecordingFwd->GetFunctionCount() == 0)
-		RETURN_META(MRES_IGNORED);
-
 	IDemoRecorder *recorder = META_IFACEPTR(IDemoRecorder);
+	CallOnStopRecording(recorder);
+	RETURN_META(MRES_IGNORED);
+}
+
+void CForwardManager::CallOnStartRecording(IDemoRecorder *recorder, const char *filename, bool bContinuously)
+{
+	if (m_StartRecordingFwd->GetFunctionCount() == 0)
+		return;
+
+	HLTVServerWrapper *wrapper = g_HLTVServers.GetWrapper(recorder);
+	int instance = -1;
+	if (wrapper)
+		instance = wrapper->GetInstanceNumber();
+
+	m_StartRecordingFwd->PushCell(instance);
+	m_StartRecordingFwd->PushString(filename);
+	m_StartRecordingFwd->Execute();
+}
+
+void CForwardManager::CallOnStopRecording(IDemoRecorder *recorder)
+{
+	if (m_StopRecordingFwd->GetFunctionCount() == 0)
+		return;
+
 	if (!recorder->IsRecording())
-		RETURN_META(MRES_IGNORED);
+		return;
 
 	char *pDemoFile = (char *)recorder->GetDemoFile();
 	
@@ -409,6 +428,87 @@ void CForwardManager::OnStopRecording_Post()
 	m_StopRecordingFwd->PushString(pDemoFile);
 	m_StopRecordingFwd->PushCell(recorder->GetRecordingTick());
 	m_StopRecordingFwd->Execute();
+}
 
-	RETURN_META(MRES_IGNORED);
-}
+// Only need to detour these on Linux. Windows always uses the vtable.
+#ifndef WIN32
+DETOUR_DECL_MEMBER2(DetourHLTVStartRecording, void, const char *, filename, bool, bContinuously)
+{
+	// Call the original first.
+	DETOUR_MEMBER_CALL(DetourHLTVStartRecording)(filename, bContinuously);
+	
+	IDemoRecorder *recorder = (IDemoRecorder *)this;
+	g_pSTVForwards.CallOnStartRecording(recorder, filename, bContinuously);
+}
+
+#if SOURCE_ENGINE == SE_CSGO
+DETOUR_DECL_MEMBER1(DetourHLTVStopRecording, void, CGameInfo const *, info)
+#else
+DETOUR_DECL_MEMBER0(DetourHLTVStopRecording, void)
+#endif
+{
+	// Call the original first.
+#if SOURCE_ENGINE == SE_CSGO
+	DETOUR_MEMBER_CALL(DetourHLTVStopRecording)(info);
+#else
+	DETOUR_MEMBER_CALL(DetourHLTVStopRecording)();
+#endif
+
+	IDemoRecorder *recorder = (IDemoRecorder *)this;
+	g_pSTVForwards.CallOnStopRecording(recorder);
+}
+
+bool CForwardManager::CreateStartRecordingDetour()
+{
+	if (m_bStartRecordingDetoured)
+		return true;
+
+	m_DStartRecording = DETOUR_CREATE_MEMBER(DetourHLTVStartRecording, "CHLTVDemoRecorder::StartRecording");
+
+	if (m_DStartRecording != nullptr)
+	{
+		m_DStartRecording->EnableDetour();
+		m_bStartRecordingDetoured = true;
+		return true;
+	}
+	smutils->LogError(myself, "CHLTVDemoRecorder::StartRecording detour could not be initialized.");
+	return false;
+}
+
+void CForwardManager::RemoveStartRecordingDetour()
+{
+	if (m_DStartRecording != nullptr)
+	{
+		m_DStartRecording->Destroy();
+		m_DStartRecording = nullptr;
+	}
+	m_bStartRecordingDetoured = false;
+}
+
+bool CForwardManager::CreateStopRecordingDetour()
+{
+	if (m_bStopRecordingDetoured)
+		return true;
+
+	m_DStopRecording = DETOUR_CREATE_MEMBER(DetourHLTVStopRecording, "CHLTVDemoRecorder::StopRecording");
+
+	if (m_DStopRecording != nullptr)
+	{
+		m_DStopRecording->EnableDetour();
+		m_bStopRecordingDetoured = true;
+		return true;
+	}
+	smutils->LogError(myself, "CHLTVDemoRecorder::StartRecording detour could not be initialized.");
+	return false;
+}
+
+void CForwardManager::RemoveStopRecordingDetour()
+{
+	if (m_DStopRecording != nullptr)
+	{
+		m_DStopRecording->Destroy();
+		m_DStopRecording = nullptr;
+	}
+	m_bStopRecordingDetoured = false;
+}
+#endif