Add macros for generating pybind11 bindings

cmake/GzPython.cmake

@@ -24,3 +24,101 @@ find_package(Python3 ${GZ_PYTHON_VERSION} QUIET)
 if(Python3_EXECUTABLE AND NOT PYTHON_EXECUTABLE)
   set(PYTHON_EXECUTABLE ${Python3_EXECUTABLE})
 endif()
+
+# Macro Definitions #
+
+#################################################
+# Insert options required to control the include of pybind11
+#
+# Usage:
+#
+#     gz_add_pybind_project_settings()
+#
+# Variables defined by this macro:
+#
+#  SKIP_PYBIND11                                Skip generating of Python bindings if OFF
+#  USE_SYSTEM_PATHS_FOR_PYTHON_INSTALLATION     Install modules in default system path if ON
+#  USE_DIST_PACKAGES_FOR_PYTHON                 Use dist-package over site-package for module installation if ON
+#
+macro(gz_add_pybind_project_settings)
+  set(skip_pybind11_default_value OFF)
+  if (MSVC)
+    # We're disabling pybind11 by default on Windows because they
+    # don't have active CI on them for now.
+    set(skip_pybind11_default_value ON)
+  endif()
+
+  option(SKIP_PYBIND11
+        "Skip generating Python bindings via pybind11"
+        ${skip_pybind11_default_value})
+
+  include(CMakeDependentOption)
+
+  cmake_dependent_option(USE_SYSTEM_PATHS_FOR_PYTHON_INSTALLATION
+        "Install Python modules in standard system paths in the system"
+        OFF "NOT SKIP_PYBIND11" OFF)
+
+  cmake_dependent_option(USE_DIST_PACKAGES_FOR_PYTHON
+        "Use dist-packages instead of site-package to install Python modules"
+        OFF "NOT SKIP_PYBIND11" OFF)
+endmacro()
+
+
+#################################################
+# Search for pybind11 and its dependencies if SKIP_PYBIND11 is not set
+#
+# Usage:
+#
+#     gz_add_pybind_project_settings() <- required!
+#     gz_search_for_pybind()
+#
+# Variables defined by this macro:
+#
+#  Python3_*            Python result variables from FindPython3 module
+#  pybind11_*           pybind11 result variables from pybind11 module
+#
+macro(gz_search_for_pybind)
+  if (SKIP_PYBIND11)
+    message(STATUS "SKIP_PYBIND11 set - disabling python bindings")
+  else()
+    find_package(Python3 ${GZ_PYTHON_VERSION} QUIET COMPONENTS Interpreter Development)
+
+    if (NOT Python3_FOUND)
+      GZ_BUILD_WARNING ("Python is missing: Python interfaces are disabled.")
+      message (STATUS "Searching for Python - not found.")
+    else()
+      message (STATUS "Searching for Python - found version ${Python3_VERSION}.")
+
+      set(PYBIND11_PYTHON_VERSION 3)
+      find_package(pybind11 CONFIG QUIET)
+
+      if (${pybind11_FOUND})
+        message (STATUS "Searching for pybind11 - found version ${pybind11_VERSION}.")
+      else()
+        GZ_BUILD_WARNING ("pybind11 is missing: Python interfaces are disabled.")
+        message (STATUS "Searching for pybind11 - not found.")
+      endif()
+    endif()
+  endif()
+endmacro()
+
+
+#################################################
+# Add the given directory to the CMake project and thus process the inner CMakeLists.txt
+# which should contain the pybind module (e.g. pybind11_add_module) instructions.
+#
+# Usage:
+#
+#     gz_add_pybind_project_settings() <- required!
+#     gz_search_for_pybind() <- required!
+#     gz_add_pybind_directory(my_bindings)
+#
+# Argument required by this macro:
+#   DIRECTORY       Path to the folder with pybind module(s)
+#
+macro(gz_add_pybind_directory DIRECTORY)
+  if (pybind11_FOUND AND NOT SKIP_PYBIND11)
+    # Bindings subdirectory
+    add_subdirectory(${DIRECTORY})
+  endif()
+endmacro()