Implement demo jump jitter fix

CMakeLists.txt

@@ -110,6 +110,7 @@ set(SPT_SOURCES
 	spt/features/game_fixes/snapshot_overflow.cpp
 	spt/features/game_fixes/vag_crash.cpp
 	spt/features/game_fixes/visual_fixes.cpp
+	spt/features/game_fixes/demo_jump_jitter.cpp
 	spt/features/visualizations/draw_ent_collides.cpp
 	spt/features/visualizations/draw_line.cpp
 	spt/features/visualizations/draw_seams.cpp

spt/features/game_fixes/demo_jump_jitter.cpp

@@ -0,0 +1,146 @@
+#include "stdafx.hpp"
+#include "..\generic.hpp"
+#include "..\sptlib-wrapper.hpp"
+#include "..\cvars.hpp"
+#include "signals.hpp"
+#include "dbg.h"
+#include "interfaces.hpp"
+#include <sstream>
+#include "thirdparty/x86.h"
+
+static void DemoJumpJitterFixCvarCallback(CON_COMMAND_CALLBACK_ARGS);
+
+ConVar spt_demo_jump_jitter_fix("spt_demo_jump_jitter_fix",
+								  "0",
+								  0,
+								  "Disables all extra movement on flashlight.",
+								  DemoJumpJitterFixCvarCallback);
+
+namespace patterns
+{
+	PATTERNS(
+		m_iv_vecViewOffset__TargetString,
+		"1",
+		"43 5F 42 61 73 65 50 6C 61 79 65 72 3A 3A 6D 5F 69 76 5F 76 65 63 56 69 65 77 4F 66 66 73 65 74");
+	PATTERNS(
+		Client__StringReferences, 
+		"1", 
+		"68", 
+		"2",
+		"C7"
+	);
+} // namespace patterns
+
+
+class DemoJumpJitterFixFeature : public FeatureWrapper<DemoJumpJitterFixFeature>
+{
+public:
+	void Toggle(bool enabled);
+
+protected:
+	virtual bool ShouldLoadFeature() override;
+	virtual void LoadFeature() override;
+	virtual void InitHooks() override;
+	virtual void UnloadFeature() override;
+
+private:
+	uintptr_t ORIG_m_iv_vecViewOffset__TargetString = 0;
+	std::vector<patterns::MatchedPattern> MATCHES_Client__StringReferences;
+
+	DECL_BYTE_REPLACE(InterpTypePush, 1, 0x12);
+};
+static DemoJumpJitterFixFeature spt_demojumpjitterfix;
+
+bool DemoJumpJitterFixFeature::ShouldLoadFeature()
+{
+	return interfaces::engine_client != nullptr;
+}
+
+void DemoJumpJitterFixFeature::InitHooks()
+{
+	FIND_PATTERN(client, m_iv_vecViewOffset__TargetString);
+	FIND_PATTERN_ALL(client, Client__StringReferences);
+}
+
+void DemoJumpJitterFixFeature::LoadFeature()
+{
+	if (!ORIG_m_iv_vecViewOffset__TargetString || MATCHES_Client__StringReferences.empty())
+		return;
+
+	GET_MODULE(client);
+
+	/*
+	* we're looking the following call:
+	* AddVar( &m_vecViewOffset, &m_iv_vecViewOffset, LATCH_SIMULATION_VAR );
+	* and changing LATCH_SIMULATION_VAR to LATCH_SIMULATION_VAR | INTERPOLATE_LINEAR_ONLY ((1 << 1) | (1 << 4))
+	* 
+	* m_iv_vecViewOffset is an IInterpolatedVar which requires a debug name on most versions
+	* so we'll hinge our search for that call from its string reference.
+	*/
+	for (auto match : MATCHES_Client__StringReferences)
+	{
+		auto strRefPtr = match.ptr;
+		uintptr_t refLocation = *(uintptr_t*)(strRefPtr + ((*(uint8_t*)strRefPtr == 0x68) ? 1 : 3));
+		if (refLocation != (uintptr_t)ORIG_m_iv_vecViewOffset__TargetString)
+			continue;
+
+		uint8_t* addr = (uint8_t*)strRefPtr;
+		for (int lenLeft = 0x200; lenLeft > 0;)
+		{
+			int len = x86_len(addr);
+			addr += len;
+			lenLeft -= len;
+
+			// outside of function now
+			if (addr[0] == X86_INT || addr[0] == X86_NOP)
+				goto end;
+
+			int offset = 1;
+			bool found =
+				// search for push 02 (6A 02)
+				(addr[0] == X86_PUSHI8 && addr[1] == 2)
+				// search for mov [reg + off],02 (c7 ?? ?? ?? 02 00 00 00)
+			    || (addr[0] == X86_MOVMIW && (offset = 4, (*(uint32_t*)(addr + 4)) == 2));
+			if (found)
+			{
+				DevMsg("Found C_BasePlayer::m_iv_vecViewOffset AddVar() type argument push at %p\n", addr);
+				INIT_BYTE_REPLACE(InterpTypePush, (uintptr_t)(addr + offset));
+				InitConcommandBase(spt_demo_jump_jitter_fix);
+				return;
+			}
+		}
+	}
+
+end:;
+	DevWarning("Couldn't find C_BasePlayer::m_iv_vecViewOffset AddVar() type argument push!\n");
+}
+
+void DemoJumpJitterFixFeature::Toggle(bool enabled)
+{
+	if (!PTR_InterpTypePush)
+	{
+		Warning("The demo jitter jump fix isn't functional at the moment.\n");
+	}
+
+	Msg("Please restart the current map or reload a save or replay the demo for the change to take effect.\n");
+
+	if (enabled)
+	{
+		DO_BYTE_REPLACE(InterpTypePush);
+		Warning("REMEMBER TO TURN THIS OFF FOR NORMAL GAMEPLAY!\n");
+	}
+	else
+	{
+		UNDO_BYTE_REPLACE(InterpTypePush);
+	}
+}
+
+void DemoJumpJitterFixCvarCallback(CON_COMMAND_CALLBACK_ARGS)
+{
+	spt_demojumpjitterfix.Toggle(((ConVar*)var)->GetBool());
+}
+
+void DemoJumpJitterFixFeature::UnloadFeature() 
+{
+	DESTROY_BYTE_REPLACE(InterpTypePush);
+}