Implement ModLoader module with engine integration

Add ModLoader module that provides Virtools engine integration and hooking capabilities. This replaces the previous BMLPlus.dll functionality by separating engine concerns from mod compatibility.

The ModLoader module includes:
- HookBlock behavior for intercepting building block execution
- CK Manager for engine lifecycle event handling
- Dynamic BML Core API loading to avoid static linking
- MinHook integration for engine function hooking
- IMC event publishing for mod lifecycle coordination

This change establishes the foundation for mod loading by providing the necessary engine integration layer while maintaining separation of concerns between the engine integration and the core mod management functionality.

Author: doyaGu

src/CMakeLists.txt

@@ -2,6 +2,7 @@ configure_file(Version.h.in "${BML_INCLUDE_DIR}/BML/Version.h" @ONLY)
 
 add_subdirectory(Utils)
 add_subdirectory(Core)
+add_subdirectory(ModLoader)
 
 set(BML_PUBLIC_HEADERS
         ${BML_INCLUDE_DIR}/BML/Version.h

src/ModLoader/Behaviors/HookBlock.cpp

@@ -0,0 +1,97 @@
+/**
+ * @file HookBlock.cpp
+ * @brief Building block hooking behavior for Virtools
+ * 
+ * This behavior allows intercepting and extending building block execution
+ * through callback registration. Used by ModLoader to provide mod callbacks
+ * at specific points in the game's behavior graph execution.
+ */
+
+#include "CKAll.h"
+
+typedef int (*CKBehaviorCallback)(const CKBehaviorContext *behcontext, void *arg);
+
+// Forward declarations
+CKObjectDeclaration *FillBehaviorHookBlockDecl();
+CKERROR CreateHookBlockProto(CKBehaviorPrototype **pproto);
+int HookBlock(const CKBehaviorContext &behcontext);
+
+/**
+ * @brief Creates the HookBlock object declaration
+ * 
+ * Registers the HookBlock building block with the Virtools engine.
+ * This block is used to intercept behavior graph execution.
+ */
+CKObjectDeclaration *FillBehaviorHookBlockDecl() {
+    CKObjectDeclaration *od = CreateCKObjectDeclaration("HookBlock");
+    od->SetDescription("Hook building blocks");
+    od->SetCategory("Hook");
+    od->SetType(CKDLL_BEHAVIORPROTOTYPE);
+    od->SetGuid(CKGUID(0x19038c0, 0x663902da));
+    od->SetAuthorGuid(CKGUID(0x3a086b4d, 0x2f4a4f01));
+    od->SetAuthorName("Kakuty");
+    od->SetVersion(0x00010000);
+    od->SetCreationFunction(CreateHookBlockProto);
+    od->SetCompatibleClassId(CKCID_BEOBJECT);
+    return od;
+}
+
+/**
+ * @brief Creates the HookBlock behavior prototype
+ * 
+ * Defines the behavior's parameters and settings:
+ * - Local parameter 0: Callback function pointer
+ * - Local parameter 1: User argument pointer
+ * - Variable inputs/outputs for flexible hooking
+ */
+CKERROR CreateHookBlockProto(CKBehaviorPrototype **pproto) {
+    CKBehaviorPrototype *proto = CreateCKBehaviorPrototype("HookBlock");
+    if (!proto) return CKERR_OUTOFMEMORY;
+
+    proto->DeclareLocalParameter("Callback", CKPGUID_POINTER);
+    proto->DeclareLocalParameter("Argument", CKPGUID_POINTER);
+
+    proto->SetBehaviorFlags((CK_BEHAVIOR_FLAGS)(CKBEHAVIOR_VARIABLEINPUTS | CKBEHAVIOR_VARIABLEOUTPUTS));
+    proto->SetFlags(CK_BEHAVIORPROTOTYPE_NORMAL);
+    proto->SetFunction(HookBlock);
+
+    *pproto = proto;
+    return CK_OK;
+}
+
+/**
+ * @brief HookBlock behavior execution function
+ * 
+ * Deactivates all inputs, invokes the registered callback (if any),
+ * then activates all outputs. The callback can control the return value.
+ * 
+ * @param behcontext The behavior context containing execution state
+ * @return CKBR_OK on success, or callback-defined return value
+ */
+int HookBlock(const CKBehaviorContext &behcontext) {
+    CKBehavior *beh = behcontext.Behavior;
+
+    // Deactivate all inputs
+    int i, count = beh->GetInputCount();
+    for (i = 0; i < count; ++i) {
+        beh->ActivateInput(i, FALSE);
+    }
+
+    // Invoke registered callback
+    int ret = CKBR_OK;
+    CKBehaviorCallback cb = nullptr;
+    beh->GetLocalParameterValue(0, &cb);
+    if (cb) {
+        void *arg = nullptr;
+        beh->GetLocalParameterValue(1, &arg);
+        ret = cb(&behcontext, arg);
+    }
+
+    // Activate all outputs
+    count = beh->GetOutputCount();
+    for (i = 0; i < count; ++i) {
+        beh->ActivateOutput(i);
+    }
+
+    return ret;
+}

src/ModLoader/Behaviors/HookBlock.h

@@ -0,0 +1,27 @@
+/**
+ * @file HookBlock.h
+ * @brief Header for HookBlock behavior
+ */
+
+#ifndef BML_MODLOADER_HOOKBLOCK_H
+#define BML_MODLOADER_HOOKBLOCK_H
+
+#include "CKAll.h"
+
+namespace ModLoader {
+
+/// Callback function type for HookBlock
+typedef int (*CKBehaviorCallback)(const CKBehaviorContext *behcontext, void *arg);
+
+/// Register HookBlock behavior with the engine
+CKObjectDeclaration *FillBehaviorHookBlockDecl();
+
+/// Create HookBlock prototype
+CKERROR CreateHookBlockProto(CKBehaviorPrototype **pproto);
+
+/// HookBlock execution function
+int HookBlock(const CKBehaviorContext &behcontext);
+
+} // namespace ModLoader
+
+#endif // BML_MODLOADER_HOOKBLOCK_H

src/ModLoader/CMakeLists.txt

@@ -0,0 +1,52 @@
+# ModLoader - Game Engine Integration Layer
+# Provides CK2 Manager, core hooks, and Virtools plugin entry points
+
+set(MODLOADER_SOURCES
+    Entry.cpp
+    ModManager.cpp
+    Behaviors/HookBlock.cpp
+)
+
+set(MODLOADER_HEADERS
+    ModManager.h
+    Behaviors/HookBlock.h
+)
+
+add_library(ModLoader SHARED
+    ${MODLOADER_SOURCES}
+    ${MODLOADER_HEADERS}
+)
+
+target_include_directories(ModLoader
+    PUBLIC
+    $<BUILD_INTERFACE:${BML_INCLUDE_DIR}>
+    $<INSTALL_INTERFACE:${CMAKE_INSTALL_INCLUDEDIR}>
+    PRIVATE
+    ${CMAKE_CURRENT_SOURCE_DIR}
+)
+
+target_link_libraries(ModLoader
+    PUBLIC
+    CK2 VxMath
+    PRIVATE
+    minhook
+)
+
+target_compile_definitions(ModLoader PRIVATE
+    MODLOADER_EXPORTS
+)
+
+set_target_properties(ModLoader PROPERTIES
+    OUTPUT_NAME "ModLoader"
+    RUNTIME_OUTPUT_DIRECTORY "${CMAKE_BINARY_DIR}/bin"
+    ARCHIVE_OUTPUT_DIRECTORY "${CMAKE_BINARY_DIR}/lib"
+    LIBRARY_OUTPUT_DIRECTORY "${CMAKE_BINARY_DIR}/lib"
+)
+
+# Install targets
+install(TARGETS ModLoader
+    EXPORT ModLoaderTargets
+    ARCHIVE DESTINATION "${CMAKE_INSTALL_LIBDIR}"
+    LIBRARY DESTINATION "${CMAKE_INSTALL_LIBDIR}"
+    RUNTIME DESTINATION "${CMAKE_INSTALL_BINDIR}"
+)