Add a pass-through renderer plugin

t5deRenderEngine.dll implements IMVU Classic's renderer plugin interface by wrapping IMVU's own OpenGL renderer, and logs what each frame calls, to prove our declarations of the interface. Built with CMake presets for 32-bit MSVC; docs/interface.md has the findings.

Co-Authored-By: Claude Opus 5.5 <[email protected]>

CMakeLists.txt

@@ -0,0 +1,47 @@
+cmake_minimum_required(VERSION 3.28)
+
+project(t5de-renderer
+    VERSION 0.1.0
+    DESCRIPTION "A new 3D renderer for the IMVU Classic client"
+    LANGUAGES CXX)
+
+# The plugin is loaded into IMVU Classic, a 32-bit program built with Visual C++: it must use the same ABI.
+if(NOT MSVC) # cl or clang-cl
+    message(FATAL_ERROR "Build with MSVC or clang-cl: the plugin must match IMVU Classic's Visual C++ ABI.")
+endif()
+if(NOT CMAKE_SIZEOF_VOID_P EQUAL 4)
+    message(FATAL_ERROR "Build for 32-bit x86 (IMVU Classic is 32-bit): use a CMakePresets.json preset.")
+endif()
+
+# The C runtime is linked statically, so the plugin needs nothing installed beside it.
+set(CMAKE_MSVC_RUNTIME_LIBRARY "MultiThreaded$<$<CONFIG:Debug>:Debug>")
+
+# Warnings and conformance for our own targets.
+add_library(t5de_options INTERFACE)
+add_library(t5de::options ALIAS t5de_options)
+target_compile_features(t5de_options INTERFACE cxx_std_20)
+target_compile_options(t5de_options INTERFACE /W4 /permissive- /utf-8 /Zc:__cplusplus)
+target_compile_definitions(t5de_options INTERFACE WIN32_LEAN_AND_MEAN NOMINMAX UNICODE _UNICODE)
+
+# Our declarations of IMVU's interfaces.
+add_library(t5de_imvu INTERFACE)
+add_library(t5de::imvu ALIAS t5de_imvu)
+target_include_directories(t5de_imvu INTERFACE
+    $<BUILD_INTERFACE:${CMAKE_CURRENT_SOURCE_DIR}/include>)
+target_compile_features(t5de_imvu INTERFACE cxx_std_20)
+
+# The renderer plugin, t5deRenderEngine.dll.
+add_library(t5de_render_engine SHARED
+    src/log.cpp
+    src/passthrough_engine.cpp
+    src/plugin.cpp
+    src/plugin.def)
+set_target_properties(t5de_render_engine PROPERTIES OUTPUT_NAME t5deRenderEngine)
+target_link_libraries(t5de_render_engine PRIVATE t5de::imvu t5de::options)
+
+install(TARGETS t5de_render_engine RUNTIME DESTINATION .)
+
+include(CTest)
+if(BUILD_TESTING)
+    add_subdirectory(tests)
+endif()