CMakeLists for large project with multiple directories?

Question

I am writing a Game Engine, which is going very well. But I am running into a problem where my CMakeLists.txt is just too messy, and I don't know enough about CMake. My project uses multiple (CMake) libraries, which are added using add_subdirectory and then target_link_libraries. My project consists of the Engine(executable), the Editor(library), and some tests/examples. Here is my file structure:

C:.
|   CMakeLists.txt
|   tree.txt
|   
+---Editor
|   |   README.md
|   |   
|   \---src
|           main.cpp
|           
+---Engine
|   |   README.md
|   |   
|   +---src
|   |   |   main.cpp
|   |   |   
|   |   +---API
|   |   |       Core.h
|   |   |       
|   |   +---App
|   |   |       Application.cpp
|   |   |       
|   |   +---ExtApp
|   |   |   |   AppInterface.cpp
|   |   |   |   
|   |   |   +---Engine
|   |   |   |       ExtAppLoader.cpp
|   |   |   |       
|   |   |   \---Game
|   |   |           InfoExport.cpp
|   |   |           
|   |   +---Framework
|   |   |       Asset.cpp
|   |   |       
|   |   +---Managing
|   |   |       AssetLoader.cpp
|   |   |       
|   |   +---Rendering
|   |   |   |   Renderer.cpp
|   |   |   |   
|   |   |   \---Renderables
|   |   |           Canvas2DRenderable.cpp
|   |   |           
|   |   \---Types
|   |           Vector3f.cpp
|   |           
|   \---TestResources
|       \---Shaders
|               Canvas2DTexturedTriangle.f
|               Canvas2DTexturedTriangle.v
|               Canvas2DUntexturedTriangle.f
|               Canvas2DUntexturedTriangle.v
|               ImTest.f
|               ImTest.v
|               
+---Libraries
|   +---glfw
|   |       CMakeLists.txt
|   |       
|   \---glm
|           CMakeLists.txt
|           
\---Tests
    \---TestGame
        \---src
                main.cpp

As you can see I have one CMakeLists at the begin, which loads all the projects. Then I have libraries, which have a CMakeLists too. Every directory has only one file to make the tree less big, but there are multiple fies in a directory. Also, here is my current, messy, almost-useless CMakeLists file:

    cmake_minimum_required(VERSION 3.6)

#project(3DEngine)



add_subdirectory(Libraries/glfw) #Add glfw to the project

# Make sure we're running C++17 so all features(like std::filesystem) are present.
set(CMAKE_CXX_STANDARD 17)
set(CMAKE_CXX_STANDARD_REQUIRED ON)
set(CMAKE_CXX_EXTENSIONS OFF)

option(BUILD_ENGINE_FOR_EDITOR "Build the engine as DLL/SO for the editor and add editor specific things. Otherwise build engine as game exec" OFF)
option(BUILD_ENGINE_FOR_DLL_APPS "Have the Engine load the game(and plugins) from dll's." ON)
project (Engine)#project engine
include_directories(Libraries/whereami/src)
include_directories(Engine/src/)
include_directories(Libraries/glfw/include)
include_directories(Libraries/glm)
include_directories(Libraries/glad/include)
include_directories(Libraries/stb)
file(GLOB EngineRootSOURCES  "Engine/src/*.cpp" "Engine/src/*.h")
file(GLOB EngineRenderingSOURCES  "Engine/src/Rendering/*.cpp" "Engine/src/Rendering/*.h")
file(GLOB EngineAppSOURCES  "Engine/src/App/*.cpp" "Engine/src/App/*.h")
file(GLOB EngineRenderingRenderablesSOURCES  "Engine/src/Rendering/Renderables/*.cpp" "Engine/src/Rendering/Renderables/*.h")
file(GLOB EngineManagingSOURCES  "Engine/src/Managing/*.cpp" "Engine/src/Managing/*.h")
file(GLOB EngineTypesSOURCES  "Engine/src/Types/*.cpp" "Engine/src/Types/*.h")
file(GLOB EngineGameEssentialsSOURCES  "Engine/src/GameEssentials/*.cpp" "Engine/src/GameEssentials/*.h")
file(GLOB EngineLibsSOURCES  "Libraries/whereami/src/whereami.c" "Libraries/glad/src/glad.c")
file(GLOB EngineFrameworkSOURCES  "Engine/src/Framework/*.h" "Engine/src/Framework/*.cpp")
file(GLOB APISOURCES  "Engine/src/API/*.cpp" "Engine/src/API/*.h")

file(GLOB EngineExtAppSOURCES "Engine/src/ExtApp/*.cpp" "Engine/src/ExtApp/*.h"
 "Engine/src/ExtApp/Interface/*.cpp" "Engine/src/ExtApp/Interface/*.h")

 file(GLOB EngineExtAppGameSOURCES "Engine/src/ExtApp/Game/*.cpp" "Engine/src/ExtApp/Game/*.h")
 source_group("ExtApp"  FILES ${EngineExtAppGameSOURCES})

 file(GLOB EngineExtAppEngineSOURCES "Engine/src/ExtApp/Engine/*.cpp" "Engine/src/ExtApp/Engine/*.h")
 source_group("ExtApp"  FILES ${EngineExtAppEngineSOURCES})

if(BUILD_ENGINE_FOR_EDITOR)
file(GLOB EngineEditorSOURCES "Engine/src/ExtApp/*.cpp" "Engine/src/ExtApp/*.h"
 "Engine/src/ExtApp/Interface/*.cpp" "Engine/src/ExtApp/Interface/*.h")


 if(BUILD_ENGINE_FOR_DLL_APPS)

 add_library(Engine SHARED ${EngineRootSOURCES} ${EngineRenderingSOURCES} ${EngineTypesSOURCES} ${EngineRenderingRenderablesSOURCES} ${EngineManagingSOURCES} ${EngineGameEssentialsSOURCES} ${EngineLibsSOURCES} ${EngineEditorSOURCES} ${EngineExtAppSOURCES} ${EngineAppSOURCES} ${APISOURCES} ${EngineExtAppEngineSOURCES} ${EngineFrameworkSOURCES})
 source_group("ExtApp"  FILES ${EngineExtAppSOURCES})
elseif(NOT BUILD_ENGINE_FOR_DLL_APPS)
add_library(Engine SHARED ${EngineRootSOURCES} ${EngineRenderingSOURCES} ${EngineTypesSOURCES} ${EngineRenderingRenderablesSOURCES} ${EngineManagingSOURCES} ${EngineGameEssentialsSOURCES} ${EngineLibsSOURCES} ${EngineEditorSOURCES} ${EngineExtAppSOURCES} ${EngineAppSOURCES} ${APISOURCES} ${EngineExtAppEngineSOURCES} ${EngineFrameworkSOURCES})
endif()



target_link_libraries(Engine glfw)
source_group("Rendering"  FILES ${EngineRenderingSOURCES})
source_group("Rendering/Renderables"  FILES ${EngineRenderingRenderablesSOURCES})
source_group("Managing"  FILES ${EngineManagingSOURCES})
source_group("App"  FILES ${EngineAppSOURCES})
source_group("Types"  FILES ${EngineTypesSOURCES})
source_group("GameEssentials"  FILES ${EngineGameEssentialsSOURCES})
source_group("Libs"  FILES ${EngineLibsSOURCES})
source_group("ExtApp"  FILES ${EngineEditorSOURCES})
source_group("API"  FILES ${APISOURCES})
source_group("Framework"  FILES ${EngineFrameworkSOURCES})
elseif(NOT BUILD_ENGINE_FOR_EDITOR)


if(BUILD_ENGINE_FOR_DLL_APPS)
file(GLOB EngineExtAppSOURCES "Engine/src/ExtApp/*.cpp" "Engine/src/ExtApp/*.h"
 "Engine/src/ExtApp/Interface/*.cpp" "Engine/src/ExtApp/Interface/*.h")
 add_executable(Engine ${EngineRootSOURCES} ${EngineRenderingSOURCES} ${EngineTypesSOURCES} ${EngineRenderingRenderablesSOURCES} ${EngineManagingSOURCES} ${EngineGameEssentialsSOURCES} ${EngineLibsSOURCES} ${EngineExtAppSOURCES} ${EngineAppSOURCES} ${APISOURCES} ${EngineExtAppEngineSOURCES} ${EngineFrameworkSOURCES})
 source_group("ExtApp"  FILES ${EngineExtAppSOURCES})
elseif(NOT BUILD_ENGINE_FOR_DLL_APPS)
add_executable(Engine ${EngineRootSOURCES} ${EngineRenderingSOURCES} ${EngineTypesSOURCES} ${EngineRenderingRenderablesSOURCES} ${EngineManagingSOURCES} ${EngineGameEssentialsSOURCES} ${EngineLibsSOURCES} ${EngineExtAppSOURCES} ${EngineAppSOURCES} ${APISOURCES} ${EngineExtAppEngineSOURCES} ${EngineFrameworkSOURCES})
endif()



target_link_libraries(Engine glfw)
source_group("Rendering"  FILES ${EngineRenderingSOURCES})
source_group("Rendering/Renderables"  FILES ${EngineRenderingRenderablesSOURCES})
source_group("Managing"  FILES ${EngineManagingSOURCES})
source_group("App"  FILES ${EngineAppSOURCES})
source_group("Types"  FILES ${EngineTypesSOURCES})
source_group("GameEssentials"  FILES ${EngineGameEssentialsSOURCES})
source_group("Libs"  FILES ${EngineLibsSOURCES})
source_group("API"  FILES ${APISOURCES})
source_group("Framework"  FILES ${EngineFrameworkSOURCES})
endif()

#add_library(Engine SHARED ${EngineSOURCES})
## END project engine

project (Module_OpenGL_Renderer_Input)#project module_renderer_opengl3
include_directories(Libraries/glfw/include)
include_directories(Libraries/glm)
include_directories(Libraries/glad/include)
include_directories(Libraries/stb)
file(GLOB Module_OpenGL_Renderer_InputSOURCES "Modules/Module_OpenGL_Renderer_Input/src/*.cpp" "Modules/Module_OpenGL_Renderer_Input/src/*.h" "Libraries/glad/src/glad.c")
add_library(Module_OpenGL_Renderer_Input SHARED ${Module_OpenGL_Renderer_InputSOURCES})
target_link_libraries(glfw)
##END project module_renderer_opengl3

project (Test1)#project test  |  This project is used to test the engine functionality.
include_directories(Libraries/imgui)
file(GLOB Test1SOURCES "Tests/Test1/src/*.cpp" "Tests/Test1/src/*.h" "Libraries/imgui/imgui*.cpp"  ${APISOURCES})
add_executable(Test1 ${Test1SOURCES})
target_link_libraries(Test1 ${CMAKE_DL_LIBS})

project (TestGame)#project test  |  This project is used to test the engine functionality.
include_directories(Libraries/imgui)
file(GLOB TestGameSOURCES "Tests/TestGame/src/*.cpp" "Tests/TestGame/src/*.h" "Libraries/imgui/imgui*.cpp" ${EngineRenderingSOURCES} ${EngineTypesSOURCES} ${EngineRenderingRenderablesSOURCES} ${EngineManagingSOURCES} ${EngineGameEssentialsSOURCES} ${EngineLibsSOURCES} ${EngineAppSOURCES}  ${APISOURCES} ${EngineExtAppSOURCES} ${EngineExtAppGameSOURCES}  ${EngineFrameworkSOURCES})
add_library(TestGame SHARED ${TestGameSOURCES})
target_link_libraries(TestGame glfw)

project (Editor)#project editor  |  This is used to make projects and build projects(using the engine)
include_directories(Libraries/imgui)
file(GLOB EditorSOURCES "Editor/src/*.cpp" "Editor/src/*.h" "Libraries/imgui/imgui*.cpp"  ${APISOURCES})
add_executable(Editor ${EditorSOURCES})

I contains lot's of things that are completely useless, or not needed anymore. So here are my questions:

1. Does every directory NEED a CMakeLists file, like I see in a lot of projects?
2. Do I need to provide every directory containing source files, or can I have it search automatically for source and header files in directories?
3. I also see that a lot of other CMake projects provide each source/header file seperately, why? Isn't that a lot of work every time you add a file?
4. Does anyone have examples of large CMake projects that I can use as a guide?
5. Is there ANYTHING else I can improve?

Thanks!

Answer 1

1. Does every directory NEED a CMakeLists file

No, that is not necessary.

It's probably a good idea to have a CMakeLists.txt for each submodule and library - and one in the root for the project itself.

2. Do I need to provide every directory containing source files, or can I have it search automatically for source and header files in directories?

Firstly, see the answer to your question 3.

Secondly, I don't see why you'd want to search for header files. Simply specify the include directories.

Finally, if you want to use globbing, it is possible to put all your source files under a single directory, and use a single glob.

3. I also see that a lot of other CMake projects provide each source ... file seperately, why?

This is what the docs say:

Note

We do not recommend using GLOB to collect a list of source files from your source tree. If no CMakeLists.txt file changes when a source is added or removed then the generated build system cannot know when to ask CMake to regenerate. The CONFIGURE_DEPENDS flag may not work reliably on all generators, or if a new generator is added in the future that cannot support it, projects using it will be stuck. Even if CONFIGURE_DEPENDS works reliably, there is still a cost to perform the check on every rebuild.

---

3. ... each header file separately, why?

I've never seen this.

5. Is there ANYTHING else I can improve?

Use target_include_directories instead of include_directories. In general, always use target_X directives.