Add more details to modules documentation, adjustments to CMake

CMakeLists.txt

@@ -1,5 +1,7 @@
 cmake_minimum_required(VERSION 4.0)
 
+project(DraconicEngine LANGUAGES C CXX)
+
 find_package(Git QUIET)
 
 if(GIT_FOUND AND EXISTS "${CMAKE_SOURCE_DIR}/.git")
@@ -15,10 +17,10 @@ if(GIT_FOUND AND EXISTS "${CMAKE_SOURCE_DIR}/.git")
     endif()
 endif()
 
-project(DraconicEngine LANGUAGES C CXX)
-
 list(APPEND CMAKE_MODULE_PATH "${PROJECT_SOURCE_DIR}/cmake")
 
 include(CTest)
+include(Compiler)
+include(Modules)
 
 add_subdirectory(engine/native)

docs/cxxmodules.md

@@ -97,4 +97,51 @@ void private_foobar()
 // foobar() is implemented in here
 void foobar()
 { /* */ }
-```
+```
+
+### How to add modules code in CMake
+
+Our `CMake` project contains scripts that make it easy to add modules to the source tree.
+
+Simply add your library containing the modules to a subdirectory
+and use the `add_modules_library` function.
+
+In this example, the library is called `my_modules`.
+It exports `module_1` and `module_2`, which in turn use `subcomponent_1`
+and `subcomponent_2` modules as well.
+Most of these modules have an internal implementation unit as discussed above.
+We also provide two unit test programs for the `my_modules` library.
+Files that end in `.test.cpp` are automatically added to CTest.
+
+```text
+my_modules/
+├── subcomponent_1/
+|   ├── subcomponent_1.cppm
+|   └── subcomponent_1.cpp
+├── subcomponent_2/
+|   ├── subcomponent_2.cppm
+|   └── subcomponent_2.cpp
+├── module_1.cppm
+├── module_1.test.cpp
+├── module_2.cppm
+├── module_2.cpp
+├── module_2.test.cpp
+└── CMakeLists.txt
+```
+
+The CMakeLists.txt in `my_modules` needs to refer to the modules libraries
+in its subdirectories.
+
+```cmake
+add_modules_library(subcomponent_1)
+add_modules_library(subcomponent_2)
+```
+
+From the parent directory of `my_modules`, simply do
+
+```cmake
+add_modules_library(my_modules)
+target_link_libraries(my_modules PUBLIC subcomponent_1 subcomponent_2)
+```
+
+This will add all the exported modules and unit test programs to the build.

engine/native/CMakeLists.txt

@@ -1,6 +1,3 @@
-include(Compiler)
-include(Modules)
-
 add_subdirectory(thirdparty SYSTEM)
 
 add_modules_library(core SHARED)