CMake Compatibility with FetchContent

[mprat]

To allow for projects using CMake's FetchContent framework, instances of CMAKE_SOURCE_DIR should be replaced with PROJECT_SOURCE_DIR. FetchContent uses add_subdirectory() under the cmake hood, and using CMAKE_SOURCE_DIR cannot be set manually; it is set as the parent project source directory. For correct add_subdirectory() cmake builds using librealsense as a dependency, these should be changed to PROJECT_SOURCE_DIR.

[maloel]

Hi @mprat
Thanks for the PR!

Question, just based on a really quick look:

PROJECT_SOURCE_DIR is the source directory of the most recent project() command.

So, for example, in a file like src/gl/CMakeLists.txt, we have:

project(realsense2-gl)
...
include(${CMAKE_SOURCE_DIR}/CMake/opengl_config.cmake)

This evaluated to the CMake directory in the root librealsense structure.
But now, if we replace by PROJECT_SOURCE_DIR, it will evaluate to src/gl/CMake/opengl_config.cmake?

[mprat]

Hi @mprat Thanks for the PR!

Question, just based on a really quick look:

PROJECT_SOURCE_DIR is the source directory of the most recent project() command.

So, for example, in a file like src/gl/CMakeLists.txt, we have:

project(realsense2-gl)
...
include(${CMAKE_SOURCE_DIR}/CMake/opengl_config.cmake)

This evaluated to the CMake directory in the root librealsense structure. But now, if we replace by PROJECT_SOURCE_DIR, it will evaluate to src/gl/CMake/opengl_config.cmake?

Not quite - the CMakeLists.txt file in src/gl/ is called by the call from add_subdirectory(src/gl) in the CMakeLists.txt in librealsense/CMakeLists.txt. According to the CMake documentation, PROJECT_SOURCE_DIR is not affected by calls to add_subdirectory() (https://cmake.org/cmake/help/latest/variable/PROJECT_SOURCE_DIR.html). This means that the previous call to project() (which appears in the top-level librealsense/CMakeLists.txt sets the PROJECT_SOURCE_DIR to librealsense/. The line in src/gl/CMakeLists.txt then will evaluate to librealsense/CMake/opengl_config.cmake, as it expected.

If you want to get rid of this ambiguity, the opengl_config.cmake can be moved into src/gl/CMake and the use of CMAKE_SOURCE_DIR/PROJECT_SOURCE_DIR can be removed completely.

[Copilot]

Pull Request Overview

This PR updates CMake configuration to improve compatibility with FetchContent by replacing CMAKE_SOURCE_DIR with PROJECT_SOURCE_DIR. This change ensures that when librealsense is used as a dependency via CMake's FetchContent framework, the build system correctly references the project's source directory rather than the parent project's directory.

• Replace CMAKE_SOURCE_DIR with PROJECT_SOURCE_DIR across multiple CMakeLists.txt files
• Update include directory paths for Python wrappers, PCL wrappers, C# bindings, and examples
• Modify CMake include statements for OpenGL configuration

Reviewed Changes

Copilot reviewed 7 out of 7 changed files in this pull request and generated 1 comment.

Show a summary per file

File	Description
wrappers/python/CMakeLists.txt	Updates include directories for pybackend2 target to use PROJECT_SOURCE_DIR
wrappers/pcl/pcl/CMakeLists.txt	Updates GLFW include directory path for rs-pcl target
wrappers/pcl/pcl-color/CMakeLists.txt	Updates GLFW include directory path for rs-pcl-color target
wrappers/csharp/Intel.RealSense/CMakeLists.txt	Updates Unity bindings directory reference
tools/CMakeLists.txt	Updates OpenGL configuration include path
src/gl/CMakeLists.txt	Updates OpenGL configuration include path
examples/CMakeLists.txt	Updates OpenGL configuration include path

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[sysrsbuild]

Can one of the admins verify this patch?

[mprat]

I've fixed the conflicts with the latest base; I am starting a new project with librealsense and would like to use this patch if possible. Can admins please verify?

[Nir-Az]

@mprat I will try to help you with that.
Can you please see the CI failures in GitHub actions after your changes?

[Nir-Az]

@mprat since we see no reggresion in our CI I will help and merge it.
Thanks for the PR,