Make PROJ the CMake project name

Allow both find_package(PROJ) and find_package(PROJ4).  More details
are in cmake/CMakeLists.txt.

1 files changed, 108 insertions, 24 deletions

diff --git a/cmake/CMakeLists.txt b/cmake/CMakeLists.txt
index 23be1f23..c790fa4a 100644
--- a/cmake/CMakeLists.txt
+++ b/cmake/CMakeLists.txt
@@ -1,9 +1,78 @@
-# proj-config.cmake for the install tree.  It's installed in
-# ${INSTALL_CMAKE_DIR} and @PROJECT_ROOT_DIR@ is the relative
-# path to the root from there.  (Note that the whole install tree can
-# be relocated.)
-file(RELATIVE_PATH PROJECT_ROOT_DIR
-  ${CMAKE_INSTALL_PREFIX}/${CMAKECONFIGDIR} ${CMAKE_INSTALL_PREFIX})
+# The old CMake PROJECT-NAME was PROJ4.
+set (PROJECT_LEGACY_NAME PROJ4)
+string (TOLOWER "${PROJECT_NAME}" PROJECT_NAME_LOWER)
+string (TOLOWER "${PROJECT_LEGACY_NAME}" PROJECT_LEGACY_LOWER)
+
+# Starting with version 7.0, we install config-style find package
+# files so that PROJ can be found with both
+#
+#   find_package(PROJ)
+#   find_package(PROJ4)
+#
+# Here are the details...  The command
+#
+#   find_package(PROJ)
+#
+# if successful, will define variables
+#
+#   PROJ_FOUND
+#   PROJ_VERSION
+#   PROJ_LIBRARIES = PROJ::proj
+#   PROJ_INCLUDE_DIRS
+#   etc
+#
+# and will define targets
+#
+#   PROJ::proj
+#   PROJ4::proj
+#
+# Similarly
+#
+#   find_package(PROJ4)
+#
+# if successful, will define variables
+#
+#   PROJ4_FOUND
+#   PROJ4_VERSION
+#   PROJ4_LIBRARIES = PROJ4::proj
+#   PROJ4_INCLUDE_DIRS
+#   etc
+#
+# and will define targets
+#
+#   PROJ::proj
+#   PROJ4::proj
+#
+# Note that targets PROJ::proj and PROJ4::proj are provided in both
+# cases.  However, no attempt is made to define both sets of variables
+# with the two find_package options.  Doing so would just lead to user
+# confusion.
+#
+# Because pre-7.0 versions of PROJ do not support find_package (PROJ)
+# and do not define a target PROJ::proj
+#
+#   find_package(PROJ4)
+#
+# (instead of PROJ) should be used in any development scenarios which
+# might involve (even indirectly) pre-7.0 versions of PROJ.
+#
+# At some future dates, find_package (PROJ4) will
+#
+#   define PROJ4_LIBRARIES = PROJ::proj
+#   give WARNING message suggesting migration to find_package(PROJ)
+#   be disallowed via the version checking code
+#
+# At some more distant date, the PROJ4::proj target will be retired.
+#
+# To support this change, the CACHE variables PROJ_CMAKE_SUBDIR (and
+# CMAKECONFIGDIR) is now the "Parent of directory to install cmake
+# config files into".
+#
+# All this messiness is confined to
+#
+#   cmake/CMakeLists.txt (this file)
+#   cmake/project-config.cmake.in
+#   cmake/project-config-version.cmake.in
 
 # Variables needed by ${PROJECT_NAME_LOWER}-config-version.cmake
 if (MSVC)
@@ -24,21 +93,36 @@ else ()
   set (CMAKE_CROSSCOMPILING_STR "OFF")
 endif ()
 
-string(TOLOWER "${PROJECT_NAME}" PROJECT_NAME_LOWER)
-configure_file(project-config.cmake.in project-config.cmake @ONLY)
-configure_file(project-config-version.cmake.in
-  project-config-version.cmake @ONLY)
-install(FILES
-  "${CMAKE_CURRENT_BINARY_DIR}/project-config.cmake"
-  DESTINATION "${CMAKECONFIGDIR}"
-  RENAME "${PROJECT_NAME_LOWER}-config.cmake")
-install(FILES
-  "${CMAKE_CURRENT_BINARY_DIR}/project-config-version.cmake"
-  DESTINATION "${CMAKECONFIGDIR}"
-  RENAME "${PROJECT_NAME_LOWER}-config-version.cmake")
-# Make information about the cmake targets (the library and the tools)
-# available.
-install(EXPORT targets
-  NAMESPACE ${PROJECT_NAME}::
-  FILE ${PROJECT_NAME_LOWER}-targets.cmake
-  DESTINATION "${CMAKECONFIGDIR}")
+foreach (PROJECT_VARIANT_NAME ${PROJECT_NAME} ${PROJECT_LEGACY_NAME})
+  string (TOLOWER "${PROJECT_VARIANT_NAME}" PROJECT_VARIANT_LOWER)
+  set (CMAKECONFIGSUBDIR "${CMAKECONFIGDIR}/${PROJECT_VARIANT_LOWER}")
+  # proj-config.cmake for the install tree.  It's installed in
+  # ${CMAKECONFIGSUBDIR} and @PROJECT_ROOT_DIR@ is the relative
+  # path to the root from there.  (Note that the whole install tree can
+  # be relocated.)
+  file (RELATIVE_PATH PROJECT_ROOT_DIR
+    ${CMAKE_INSTALL_PREFIX}/${CMAKECONFIGSUBDIR} ${CMAKE_INSTALL_PREFIX})
+  configure_file (project-config.cmake.in
+    project-${PROJECT_VARIANT_LOWER}-config.cmake @ONLY)
+  configure_file (project-config-version.cmake.in
+    project-${PROJECT_VARIANT_LOWER}-version.cmake @ONLY)
+  install(FILES
+    "${CMAKE_CURRENT_BINARY_DIR}/project-${PROJECT_VARIANT_LOWER}-config.cmake"
+    DESTINATION "${CMAKECONFIGSUBDIR}"
+    RENAME "${PROJECT_VARIANT_LOWER}-config.cmake")
+  install(FILES
+    "${CMAKE_CURRENT_BINARY_DIR}/project-${PROJECT_VARIANT_LOWER}-version.cmake"
+    DESTINATION "${CMAKECONFIGSUBDIR}"
+    RENAME "${PROJECT_VARIANT_LOWER}-config-version.cmake")
+  # Make information about the cmake targets (the library and the tools)
+  # available.
+  install(EXPORT targets
+    NAMESPACE ${PROJECT_NAME}::
+    FILE ${PROJECT_NAME_LOWER}-targets.cmake
+    DESTINATION "${CMAKECONFIGSUBDIR}")
+  install(EXPORT targets
+    NAMESPACE ${PROJECT_LEGACY_NAME}::
+    FILE ${PROJECT_LEGACY_LOWER}-targets.cmake
+    DESTINATION "${CMAKECONFIGSUBDIR}")
+endforeach ()
+