Re-add LSL_BUILD_EXAMPLES option

Add an opt-in LSL_BUILD_EXAMPLES option (default OFF) to build the
examples alongside liblsl.

Examples can also still be configured as a standalone project to test
the installed CMake package. In standalone mode, the examples use
find_package(LSL) and install their targets; when included in the
liblsl build, they link directly to the existing LSL::lsl target.

The option was added in 70cc090 and
removed in 5758c64 because the
examples relied on in-tree artifacts, which could mask installation
issues.

Author: myd7349

CMakeLists.txt

@@ -32,6 +32,10 @@ if(LSL_UNITTESTS AND NOT IOS)
 	add_subdirectory(testing)
 endif()
 
+if(LSL_BUILD_EXAMPLES)
+    add_subdirectory(examples)
+endif()
+
 # Config for packaging
 include(cmake/LSLCMake.cmake)
 LSL_get_target_arch()

cmake/ProjectOptions.cmake

@@ -11,6 +11,7 @@ option(LSL_LEGACY_CPP_ABI "Build legacy C++ ABI into lsl-static" OFF)
 option(LSL_OPTIMIZATIONS "Enable some more compiler optimizations" ON)
 option(LSL_BUNDLED_BOOST "Use the bundled Boost by default" ON)
 option(LSL_FETCH_PUGIXML "Fetch pugixml via FetchContent instead of using system package" ON)
+option(LSL_BUILD_EXAMPLES "Build example programs in examples/" OFF)
 cmake_dependent_option(LSL_TOOLS "Build some experimental tools for in-depth tests" OFF "CMAKE_SOURCE_DIR STREQUAL PROJECT_SOURCE_DIR" OFF)
 cmake_dependent_option(LSL_UNITTESTS "Build LSL library unit tests" OFF "CMAKE_SOURCE_DIR STREQUAL PROJECT_SOURCE_DIR" OFF)
 cmake_dependent_option(LSL_INSTALL "Generate install targets" ON "CMAKE_SOURCE_DIR STREQUAL PROJECT_SOURCE_DIR" OFF)

examples/CMakeLists.txt

@@ -3,38 +3,40 @@ project(lslexamples
 	LANGUAGES C CXX
 	VERSION 0.2.0)
 
-include(GNUInstallDirs)
+if(PROJECT_IS_TOP_LEVEL)
+    include(GNUInstallDirs)
 
-set(LSL_SEARCH_PATHS
-    ${LSL_INSTALL_ROOT}
-    "${CMAKE_CURRENT_LIST_DIR}/../install"  # GHA scripts default install directory
-    "${CMAKE_CURRENT_LIST_DIR}/../cmake-build-release/install"  # CLion default if using -DCMAKE_INSTALL_PREFIX=install
-)
-if(APPLE)
-    # Also search in a Frameworks subdirectory for each path
-    foreach(p IN LISTS LSL_SEARCH_PATHS)
-        if(p)
-            list(APPEND LSL_SEARCH_PATHS "${p}/Frameworks")
-        endif()
-    endforeach()
-else()
-    # Add MSVC-specific paths if not on Apple
-    list(APPEND LSL_SEARCH_PATHS
-        "${CMAKE_CURRENT_LIST_DIR}/../cmake-build-release-visual-studio/install"  # CLion default if using VS compiler
-        "${CMAKE_CURRENT_LIST_DIR}/../out/build/x64-Release/install"  # MSVC default if using -DCMAKE_INSTALL_PREFIX=install
+    set(LSL_SEARCH_PATHS
+        ${LSL_INSTALL_ROOT}
+        "${CMAKE_CURRENT_LIST_DIR}/../install"  # GHA scripts default install directory
+        "${CMAKE_CURRENT_LIST_DIR}/../cmake-build-release/install"  # CLion default if using -DCMAKE_INSTALL_PREFIX=install
     )
-endif()
+    if(APPLE)
+        # Also search in a Frameworks subdirectory for each path
+        foreach(p IN LISTS LSL_SEARCH_PATHS)
+            if(p)
+                list(APPEND LSL_SEARCH_PATHS "${p}/Frameworks")
+            endif()
+        endforeach()
+    else()
+        # Add MSVC-specific paths if not on Apple
+        list(APPEND LSL_SEARCH_PATHS
+            "${CMAKE_CURRENT_LIST_DIR}/../cmake-build-release-visual-studio/install"  # CLion default if using VS compiler
+            "${CMAKE_CURRENT_LIST_DIR}/../out/build/x64-Release/install"  # MSVC default if using -DCMAKE_INSTALL_PREFIX=install
+        )
+    endif()
 
-find_package(LSL REQUIRED
-	HINTS ${LSL_SEARCH_PATHS}
-	PATH_SUFFIXES share/LSL
-)
-get_filename_component(LSL_PATH ${LSL_CONFIG} DIRECTORY)
-message(STATUS "Found LSL lib in ${LSL_PATH}")
+    find_package(LSL REQUIRED
+	    HINTS ${LSL_SEARCH_PATHS}
+	    PATH_SUFFIXES share/LSL
+    )
+    get_filename_component(LSL_PATH ${LSL_CONFIG} DIRECTORY)
+    message(STATUS "Found LSL lib in ${LSL_PATH}")
 
-# Include the LSLCMake.cmake file, just for testing.
-# This doesn't do much for us now that we don't use installLSLApp() anymore.
-include("${LSL_PATH}/LSLCMake.cmake")
+    # Include the LSLCMake.cmake file, just for testing.
+    # This doesn't do much for us now that we don't use installLSLApp() anymore.
+    include("${LSL_PATH}/LSLCMake.cmake")
+endif()
 
 # convenience function to add an example file
 # this creates a target, links the necessary libraries and
@@ -65,10 +67,12 @@ function(addlslexample name extension)
 #        )
 #    endif()
 
-    install(TARGETS ${name}
-        COMPONENT ${PROJECT_NAME}
-        RUNTIME DESTINATION ${CMAKE_INSTALL_BINDIR}
-    )
+    if(PROJECT_IS_TOP_LEVEL)
+        install(TARGETS ${name}
+            COMPONENT ${PROJECT_NAME}
+            RUNTIME DESTINATION ${CMAKE_INSTALL_BINDIR}
+        )
+    endif()
 endfunction()
 
 find_package(Threads)
@@ -107,9 +111,12 @@ if(WIN32)
         $<TARGET_FILE_DIR:HandleMetaData>
         COMMENT "Copying lsl.dll to examples build directory"
     )
-	# Install the lsl.dll to the same directory as the executable.
-	install(
-        CODE "file(INSTALL DESTINATION \"${CMAKE_INSTALL_PREFIX}/${CMAKE_INSTALL_BINDIR}\" TYPE SHARED_LIBRARY FILES \"$<TARGET_FILE:LSL::lsl>\")"
-        COMPONENT ${PROJECT_NAME}
-    )
+
+    if(PROJECT_IS_TOP_LEVEL)
+	    # Install the lsl.dll to the same directory as the executable.
+	    install(
+            CODE "file(INSTALL DESTINATION \"${CMAKE_INSTALL_PREFIX}/${CMAKE_INSTALL_BINDIR}\" TYPE SHARED_LIBRARY FILES \"$<TARGET_FILE:LSL::lsl>\")"
+            COMPONENT ${PROJECT_NAME}
+        )
+    endif()
 endif()