cmake: added Eigen3::Eigen imported target

CMakeLists.txt

@@ -510,7 +510,50 @@ set ( EIGEN_INCLUDE_DIR "${CMAKE_INSTALL_PREFIX}/${INCLUDE_INSTALL_DIR}" )
 set ( EIGEN_INCLUDE_DIRS ${EIGEN_INCLUDE_DIR} )
 set ( EIGEN_ROOT_DIR ${CMAKE_INSTALL_PREFIX} )
 
-configure_file ( ${CMAKE_CURRENT_SOURCE_DIR}/cmake/Eigen3Config.cmake.in
+# Interface libraries require at least CMake 3.0
+if (NOT CMAKE_VERSION VERSION_LESS 3.0)
+  include (CMakePackageConfigHelpers)
+
+  # Imported target support
+  add_library (eigen INTERFACE)
+
+  target_compile_definitions (eigen INTERFACE ${EIGEN_DEFINITIONS})
+  target_include_directories (eigen INTERFACE
+    $<BUILD_INTERFACE:${CMAKE_CURRENT_SOURCE_DIR}>
+    $<INSTALL_INTERFACE:${INCLUDE_INSTALL_DIR}>
+  )
+
+  # Export as title case Eigen
+  set_target_properties (eigen PROPERTIES EXPORT_NAME Eigen)
+
+  install (TARGETS eigen EXPORT Eigen3Targets)
+
+  configure_package_config_file (
+    ${CMAKE_CURRENT_SOURCE_DIR}/cmake/Eigen3Config.cmake.in
+    ${CMAKE_CURRENT_BINARY_DIR}/Eigen3Config.cmake
+    INSTALL_DESTINATION ${CMAKEPACKAGE_INSTALL_DIR}
+    NO_CHECK_REQUIRED_COMPONENTS_MACRO # Eigen does not provide components
+  )
+  write_basic_package_version_file (Eigen3ConfigVersion.cmake
+    VERSION ${EIGEN_VERSION_NUMBER} COMPATIBILITY SameMajorVersion)
+
+  # The Eigen target will be located in the Eigen3 namespace. Other CMake
+  # targets can refer to it using Eigen3::Eigen.
+  export (TARGETS eigen NAMESPACE Eigen3:: FILE Eigen3Targets.cmake)
+  # Export Eigen3 package to CMake registry such that it can be easily found by
+  # CMake even if it has not been installed to a standard directory.
+  export (PACKAGE Eigen3)
+
+  install (EXPORT Eigen3Targets NAMESPACE Eigen3:: DESTINATION
+    ${CMAKEPACKAGE_INSTALL_DIR})
+  install (FILES
+    ${CMAKE_CURRENT_BINARY_DIR}/Eigen3Config.cmake
+    ${CMAKE_CURRENT_BINARY_DIR}/Eigen3ConfigVersion.cmake
+    ${CMAKE_CURRENT_SOURCE_DIR}/cmake/UseEigen3.cmake
+    DESTINATION ${CMAKEPACKAGE_INSTALL_DIR})
+else (NOT CMAKE_VERSION VERSION_LESS 3.0)
+  # Fallback to legacy Eigen3Config.cmake without the imported target
+  configure_file ( ${CMAKE_CURRENT_SOURCE_DIR}/cmake/Eigen3ConfigLegacy.cmake.in
                    ${CMAKE_CURRENT_BINARY_DIR}/Eigen3Config.cmake
                    @ONLY ESCAPE_QUOTES
                  )
@@ -519,6 +562,7 @@ install ( FILES ${CMAKE_CURRENT_SOURCE_DIR}/cmake/UseEigen3.cmake
                   ${CMAKE_CURRENT_BINARY_DIR}/Eigen3Config.cmake
             DESTINATION ${CMAKEPACKAGE_INSTALL_DIR}
           )
+endif (NOT CMAKE_VERSION VERSION_LESS 3.0)
 
 # Add uninstall target
 add_custom_target ( uninstall

cmake/Eigen3Config.cmake.in

@@ -1,18 +1,11 @@
-#                                               -*- cmake -*-
-#
-#  Eigen3Config.cmake(.in)
+# This file exports the Eigen3::Eigen CMake target which should be passed to the
+# target_link_libraries command.
 
-# Use the following variables to compile and link against Eigen:
-#  EIGEN3_FOUND              - True if Eigen was found on your system
-#  EIGEN3_USE_FILE           - The file making Eigen usable
-#  EIGEN3_DEFINITIONS        - Definitions needed to build with Eigen
-#  EIGEN3_INCLUDE_DIR        - Directory where signature_of_eigen3_matrix_library can be found
-#  EIGEN3_INCLUDE_DIRS       - List of directories of Eigen and it's dependencies
-#  EIGEN3_ROOT_DIR           - The base directory of Eigen
-#  EIGEN3_VERSION_STRING     - A human-readable string containing the version
-#  EIGEN3_VERSION_MAJOR      - The major version of Eigen
-#  EIGEN3_VERSION_MINOR      - The minor version of Eigen
-#  EIGEN3_VERSION_PATCH      - The patch version of Eigen
+@PACKAGE_INIT@
+
+include ("${CMAKE_CURRENT_LIST_DIR}/Eigen3Targets.cmake")
+
+# Legacy variables, do *not* use. May be removed in the future.
 
 set (EIGEN3_FOUND 1)
 set (EIGEN3_USE_FILE    "${CMAKE_CURRENT_LIST_DIR}/UseEigen3.cmake")

cmake/Eigen3ConfigLegacy.cmake.in

@@ -0,0 +1,28 @@
+#                                               -*- cmake -*-
+#
+#  Eigen3Config.cmake(.in)
+
+# Use the following variables to compile and link against Eigen:
+#  EIGEN3_FOUND              - True if Eigen was found on your system
+#  EIGEN3_USE_FILE           - The file making Eigen usable
+#  EIGEN3_DEFINITIONS        - Definitions needed to build with Eigen
+#  EIGEN3_INCLUDE_DIR        - Directory where signature_of_eigen3_matrix_library can be found
+#  EIGEN3_INCLUDE_DIRS       - List of directories of Eigen and it's dependencies
+#  EIGEN3_ROOT_DIR           - The base directory of Eigen
+#  EIGEN3_VERSION_STRING     - A human-readable string containing the version
+#  EIGEN3_VERSION_MAJOR      - The major version of Eigen
+#  EIGEN3_VERSION_MINOR      - The minor version of Eigen
+#  EIGEN3_VERSION_PATCH      - The patch version of Eigen
+
+set ( EIGEN3_FOUND 1 )
+set ( EIGEN3_USE_FILE     "${CMAKE_CURRENT_LIST_DIR}/UseEigen3.cmake" )
+
+set ( EIGEN3_DEFINITIONS  "@EIGEN_DEFINITIONS@" )
+set ( EIGEN3_INCLUDE_DIR  "@EIGEN_INCLUDE_DIR@" )
+set ( EIGEN3_INCLUDE_DIRS "@EIGEN_INCLUDE_DIRS@" )
+set ( EIGEN3_ROOT_DIR     "@EIGEN_ROOT_DIR@" )
+
+set ( EIGEN3_VERSION_STRING "@EIGEN_VERSION_STRING@" )
+set ( EIGEN3_VERSION_MAJOR  "@EIGEN_VERSION_MAJOR@" )
+set ( EIGEN3_VERSION_MINOR  "@EIGEN_VERSION_MINOR@" )
+set ( EIGEN3_VERSION_PATCH  "@EIGEN_VERSION_PATCH@" )

doc/Manual.dox

@@ -26,6 +26,7 @@ namespace Eigen {
   - \subpage TopicPitfalls
   - \subpage TopicTemplateKeyword
   - \subpage UserManual_UnderstandingEigen
+  - \subpage TopicCMakeGuide
 */
 
 /** \page UserManual_UnderstandingEigen Understanding Eigen

doc/TopicCMakeGuide.dox

@@ -0,0 +1,40 @@
+namespace Eigen {
+
+/**
+
+\page TopicCMakeGuide Using %Eigen in CMake Projects
+
+%Eigen provides native CMake support which allows the library to be easily
+used in CMake projects.
+
+\note %CMake 3.0 (or later) is required to enable this functionality.
+
+%Eigen exports a CMake target called `Eigen3::Eigen` which can be imported
+using the `find_package` CMake command and used by calling
+`target_link_libraries` as in the following example:
+\code{.cmake}
+cmake_minimum_required (VERSION 3.0)
+project (myproject)
+
+find_package (Eigen3 3.3 REQUIRED)
+
+add_executable (example example.cpp)
+target_link_libraries (example Eigen3::Eigen)
+\endcode
+
+The above code snippet must be placed in a file called `CMakeLists.txt` alongside
+`example.cpp`. After running
+\code{.sh}
+$ cmake path-to-example-directory
+\endcode
+CMake will produce project files that generate an executable called `example`
+which requires at least version 3.3 of %Eigen. Here, `path-to-example-directory`
+is the path to the directory that contains both `CMakeLists.txt` and
+`example.cpp`.
+
+
+*/
+
+}
+
+// vim: set ft=cpp.doxygen