add findlibxml2 script for outdated versions of cmake

cmake/FindLibXml2.cmake

@@ -0,0 +1,131 @@
+# Distributed under the OSI-approved BSD 3-Clause License.  See accompanying
+# file Copyright.txt or https://cmake.org/licensing for details.
+
+#[=======================================================================[.rst:
+FindLibXml2
+-----------
+
+Find the XML processing library (libxml2).
+
+Imported Targets
+^^^^^^^^^^^^^^^^
+
+.. versionadded:: 3.12
+
+The following :prop_tgt:`IMPORTED` targets may be defined:
+
+``LibXml2::LibXml2``
+  libxml2 library.
+``LibXml2::xmllint``
+  .. versionadded:: 3.17
+
+  xmllint command-line executable.
+
+Result variables
+^^^^^^^^^^^^^^^^
+
+This module will set the following variables in your project:
+
+``LibXml2_FOUND``
+  true if libxml2 headers and libraries were found
+``LIBXML2_INCLUDE_DIR``
+  the directory containing LibXml2 headers
+``LIBXML2_INCLUDE_DIRS``
+  list of the include directories needed to use LibXml2
+``LIBXML2_LIBRARIES``
+  LibXml2 libraries to be linked
+``LIBXML2_DEFINITIONS``
+  the compiler switches required for using LibXml2
+``LIBXML2_XMLLINT_EXECUTABLE``
+  path to the XML checking tool xmllint coming with LibXml2
+``LIBXML2_VERSION_STRING``
+  the version of LibXml2 found (since CMake 2.8.8)
+
+Cache variables
+^^^^^^^^^^^^^^^
+
+The following cache variables may also be set:
+
+``LIBXML2_INCLUDE_DIR``
+  the directory containing LibXml2 headers
+``LIBXML2_LIBRARY``
+  path to the LibXml2 library
+#]=======================================================================]
+
+cmake_policy(PUSH)
+cmake_policy(SET CMP0159 NEW) # file(STRINGS) with REGEX updates CMAKE_MATCH_<n>
+
+# use pkg-config to get the directories and then use these values
+# in the find_path() and find_library() calls
+find_package(PkgConfig QUIET)
+if(PKG_CONFIG_FOUND)
+  pkg_check_modules(PC_LIBXML QUIET libxml-2.0)
+endif()
+
+find_path(LIBXML2_INCLUDE_DIR NAMES libxml/xpath.h
+   HINTS
+   ${PC_LIBXML_INCLUDEDIR}
+   ${PC_LIBXML_INCLUDE_DIRS}
+   PATH_SUFFIXES libxml2
+   )
+
+# CMake 3.9 and below used 'LIBXML2_LIBRARIES' as the name of
+# the cache entry storing the find_library result.  Use the
+# value if it was set by the project or user.
+if(DEFINED LIBXML2_LIBRARIES AND NOT DEFINED LIBXML2_LIBRARY)
+  set(LIBXML2_LIBRARY ${LIBXML2_LIBRARIES})
+endif()
+
+find_library(LIBXML2_LIBRARY NAMES xml2 libxml2 libxml2_a
+   HINTS
+   ${PC_LIBXML_LIBDIR}
+   ${PC_LIBXML_LIBRARY_DIRS}
+   )
+
+find_program(LIBXML2_XMLLINT_EXECUTABLE xmllint)
+# for backwards compat. with KDE 4.0.x:
+set(XMLLINT_EXECUTABLE "${LIBXML2_XMLLINT_EXECUTABLE}")
+
+if(LIBXML2_INCLUDE_DIR AND EXISTS "${LIBXML2_INCLUDE_DIR}/libxml/xmlversion.h")
+    file(STRINGS "${LIBXML2_INCLUDE_DIR}/libxml/xmlversion.h" libxml2_version_str
+         REGEX "^#define[\t ]+LIBXML_DOTTED_VERSION[\t ]+\".*\"")
+
+    string(REGEX REPLACE "^#define[\t ]+LIBXML_DOTTED_VERSION[\t ]+\"([^\"]*)\".*" "\\1"
+           LIBXML2_VERSION_STRING "${libxml2_version_str}")
+    unset(libxml2_version_str)
+endif()
+
+set(LIBXML2_INCLUDE_DIRS ${LIBXML2_INCLUDE_DIR})
+set(LIBXML2_LIBRARIES ${LIBXML2_LIBRARY})
+
+# Did we find the same installation as pkg-config?
+# If so, use additional information from it.
+unset(LIBXML2_DEFINITIONS)
+foreach(libxml2_pc_lib_dir IN LISTS PC_LIBXML_LIBDIR PC_LIBXML_LIBRARY_DIRS)
+  if (LIBXML2_LIBRARY MATCHES "^${libxml2_pc_lib_dir}")
+    list(APPEND LIBXML2_INCLUDE_DIRS ${PC_LIBXML_INCLUDE_DIRS})
+    set(LIBXML2_DEFINITIONS ${PC_LIBXML_CFLAGS_OTHER})
+    break()
+  endif()
+endforeach()
+
+include(FindPackageHandleStandardArgs)
+find_package_handle_standard_args(LibXml2
+                                  REQUIRED_VARS LIBXML2_LIBRARY LIBXML2_INCLUDE_DIR
+                                  VERSION_VAR LIBXML2_VERSION_STRING)
+
+mark_as_advanced(LIBXML2_INCLUDE_DIR LIBXML2_LIBRARY LIBXML2_XMLLINT_EXECUTABLE)
+
+if(LibXml2_FOUND AND NOT TARGET LibXml2::LibXml2)
+  add_library(LibXml2::LibXml2 UNKNOWN IMPORTED)
+  set_target_properties(LibXml2::LibXml2 PROPERTIES INTERFACE_INCLUDE_DIRECTORIES "${LIBXML2_INCLUDE_DIRS}")
+  set_target_properties(LibXml2::LibXml2 PROPERTIES INTERFACE_COMPILE_OPTIONS "${LIBXML2_DEFINITIONS}")
+  set_property(TARGET LibXml2::LibXml2 APPEND PROPERTY IMPORTED_LOCATION "${LIBXML2_LIBRARY}")
+endif()
+
+if(LIBXML2_XMLLINT_EXECUTABLE AND NOT TARGET LibXml2::xmllint)
+  add_executable(LibXml2::xmllint IMPORTED)
+  set_target_properties(LibXml2::xmllint PROPERTIES IMPORTED_LOCATION "${LIBXML2_XMLLINT_EXECUTABLE}")
+endif()
+
+cmake_policy(POP)

rpi/CMakeLists.txt

@@ -240,7 +240,7 @@ endif()
 
 # Find libxml2 (used for storing/parsing user config)
 if (NOT VANILLA_BUILD_VENDORED)
-    find_package(libxml2 REQUIRED)
+    find_package(LibXml2 REQUIRED)
 endif()
 
 target_link_libraries(vanilla-pi PRIVATE LibXml2::LibXml2)