Add replace_traintrack_file manifest statement and 90% of patch to ut…

…ilize it; patch just needs the pattern of the native that loads traintracks.xml

code/components/citizen-resources-gta/src/ResourcesTest.cpp

@@ -57,6 +57,7 @@ namespace streaming
 	void RemoveDataFileFromLoadList(const std::string& type, const std::string& path);
 
 	void SetNextLevelPath(const std::string& path);
+	void SetTrainTrackFilePath(const std::string& path);
 }
 #endif
 
@@ -188,6 +189,11 @@ static InitFunction initFunction([] ()
 				streaming::SetNextLevelPath(resourceRoot + meta.second);
 			}
 
+			for (auto& meta : metaData->GetEntries("replace_traintrack_file"))
+			{
+				streaming::SetTrainTrackFilePath(resourceRoot + meta.second);
+			}
+
 			if (!RangeLengthMatches(metaData->GetEntries("data_file"), metaData->GetEntries("data_file_extra")))
 			{
 				GlobalError("data_file entry count mismatch in resource %s", resource->GetName());

code/components/gta-core-rdr3/src/PatchTrainTrackFileOverride.cpp

@@ -0,0 +1,50 @@
+#include <StdInc.h>
+#include <Hooking.h>
+
+#include "Hooking.Stubs.h"
+#include "Hooking.Patterns.h"
+
+static std::string g_overrideTrainTrackFile = "";
+
+//
+// The nodes that define the various railroads that trains can follow are defined by *.dat files stored at common:/data/levels/rdr3/.
+// These *.dat files are in turn referenced by filename by traintracks.xml, which is also at common:/data/levels/rdr3/.
+// The mounter for traintracks.xml, CTrainConfigFileMounter, does not clear the array of track data on subsequent calls; it simply
+// adds the tracks to the end of the array. This is an issue, because in order for custom tracks to interface properly with the base-game tracks,
+// both of them must be modified to reference each other; and as it stands, there is no way to straight-up replace base-game track data short
+// of replacing the level meta... but there are blocking issues on getting that to work with RDR3, so that is not currently an option.
+// 
+// So here we introduce an fxmanifest statement, "replace_traintrack_file", which takes the path to a custom traintracks.xml and stores
+// it to a global variable. CTrainConfigFileMounter is then patched to check if this global is empty, and if so, the track loading function
+// is passed the path to the base-game traintracks.xml. Otherwise, the function is given the path to the custom XML file in the resource
+// it is located in.
+//
+
+namespace streaming
+{
+	void DLL_EXPORT SetTrainTrackFilePath(const std::string& path)
+	{
+		g_overrideTrainTrackFile = path;
+	}
+}
+
+static void (*g_origLoadTrainTracks)(void*);
+static void LoadTrainTracks(void* a1)
+{
+    if (g_overrideTrainTrackFile.empty())
+    {
+        g_origLoadTrainTracks(a1);
+    }
+	else
+	{
+		g_origLoadTrainTracks(g_overrideTrainTrackFile.data());
+	}
+}
+
+static HookFunction hookFunction([]()
+{
+	{
+        auto location = hook::get_pattern("");
+        g_origLoadTrainTracks = hook::trampoline(location, LoadTrainTracks);
+	}
+});