FindGLEW: Update implementation

Replicate behaviour of upstream GLEW.

* define the imported target GLEW::glew for the shared library GLEW

* if GLEW_USE_STATIC_LIBS is defined and set to TRUE, this module instead
  defines the imported target GLEW::glew_s for the static library GLEW

* an imported target GLEW::GLEW is created as a copy of either GLEW::glew
  or GLEW::glew_s

* by setting GLEW_VERBOSE you print out the log of the module.

Fixes: #17638, #17864, #18989

Help/release/dev/FindGLEW-updates.rst

@@ -0,0 +1,5 @@
+FindGLEW-updates
+----------------
+
+* The :module:`FindGLEW` module now provides an interface more consistent
+  with what upstream GLEW provides in its own CMake package files.

Modules/FindGLEW.cmake

@@ -7,64 +7,300 @@ FindGLEW
 
 Find the OpenGL Extension Wrangler Library (GLEW)
 
-IMPORTED Targets
+Input Variables
+^^^^^^^^^^^^^^^
+
+The following variables may be set to influence this module’s behavior:
+
+``GLEW_USE_STATIC_LIBS``
+  to find and create :prop_tgt:`IMPORTED` target for static linkage.
+
+``GLEW_VERBOSE``
+  to output a detailed log of this module.
+
+Imported Targets
 ^^^^^^^^^^^^^^^^
 
-This module defines the :prop_tgt:`IMPORTED` target ``GLEW::GLEW``,
-if GLEW has been found.
+This module defines the following :ref:`Imported Targets <Imported Targets>`:
+
+
+``GLEW::glew``
+  The GLEW shared library.
+``GLEW::glew_s``
+  The GLEW static library, if ``GLEW_USE_STATIC_LIBS`` is set to ``TRUE``.
+``GLEW::GLEW``
+  Duplicates either ``GLEW::glew`` or ``GLEW::glew_s`` based on availability.
 
 Result Variables
 ^^^^^^^^^^^^^^^^
 
 This module defines the following variables:
 
-::
+``GLEW_INCLUDE_DIRS``
+  include directories for GLEW
+``GLEW_LIBRARIES``
+  libraries to link against GLEW
+``GLEW_SHARED_LIBRARIES``
+  libraries to link against shared GLEW
+``GLEW_STATIC_LIBRARIES``
+  libraries to link against static GLEW
+``GLEW_FOUND``
+  true if GLEW has been found and can be used
+``GLEW_VERSION``
+  GLEW version
+``GLEW_VERSION_MAJOR``
+  GLEW major version
+``GLEW_VERSION_MINOR``
+  GLEW minor version
+``GLEW_VERSION_MICRO``
+  GLEW micro version
 
-  GLEW_INCLUDE_DIRS - include directories for GLEW
-  GLEW_LIBRARIES - libraries to link against GLEW
-  GLEW_FOUND - true if GLEW has been found and can be used
 #]=======================================================================]
 
+include(${CMAKE_CURRENT_LIST_DIR}/FindPackageHandleStandardArgs.cmake)
+
+find_package(GLEW CONFIG QUIET)
+
+if(GLEW_FOUND)
+  find_package_handle_standard_args(GLEW DEFAULT_MSG GLEW_CONFIG)
+  return()
+endif()
+
+if(GLEW_VERBOSE)
+  message(STATUS "FindGLEW: did not find GLEW CMake config file. Searching for libraries.")
+endif()
+
+
+function(__glew_set_find_library_suffix shared_or_static)
+  if(UNIX AND "${shared_or_static}" MATCHES "SHARED")
+    set(CMAKE_FIND_LIBRARY_SUFFIXES ".so" PARENT_SCOPE)
+  elseif(UNIX AND "${shared_or_static}" MATCHES "STATIC")
+    set(CMAKE_FIND_LIBRARY_SUFFIXES ".a" PARENT_SCOPE)
+  elseif(APPLE AND "${shared_or_static}" MATCHES "SHARED")
+    set(CMAKE_FIND_LIBRARY_SUFFIXES ".dylib;.so" PARENT_SCOPE)
+  elseif(APPLE AND "${shared_or_static}" MATCHES "STATIC")
+    set(CMAKE_FIND_LIBRARY_SUFFIXES ".a" PARENT_SCOPE)
+  elseif(WIN32 AND "${shared_or_static}" MATCHES "SHARED")
+    set(CMAKE_FIND_LIBRARY_SUFFIXES ".lib" PARENT_SCOPE)
+  elseif(WIN32 AND "${shared_or_static}" MATCHES "STATIC")
+    set(CMAKE_FIND_LIBRARY_SUFFIXES ".lib;.dll.a" PARENT_SCOPE)
+  endif()
+
+  if(GLEW_VERBOSE)
+    message(STATUS "FindGLEW: CMAKE_FIND_LIBRARY_SUFFIXES for ${shared_or_static}: ${CMAKE_FIND_LIBRARY_SUFFIXES}")
+  endif()
+endfunction()
+
+
+if(GLEW_VERBOSE)
+  if(DEFINED GLEW_USE_STATIC_LIBS)
+    message(STATUS "FindGLEW: GLEW_USE_STATIC_LIBS: ${GLEW_USE_STATIC_LIBS}.")
+  else()
+    message(STATUS "FindGLEW: GLEW_USE_STATIC_LIBS is undefined. Treated as FALSE.")
+  endif()
+endif()
+
 find_path(GLEW_INCLUDE_DIR GL/glew.h)
+mark_as_advanced(GLEW_INCLUDE_DIR)
 
-if(NOT GLEW_LIBRARY)
-  find_library(GLEW_LIBRARY_RELEASE NAMES GLEW glew32 glew glew32s PATH_SUFFIXES lib64 libx32)
-  find_library(GLEW_LIBRARY_DEBUG NAMES GLEWd glew32d glewd PATH_SUFFIXES lib64)
+set(GLEW_INCLUDE_DIRS ${GLEW_INCLUDE_DIR})
 
-  include(${CMAKE_CURRENT_LIST_DIR}/SelectLibraryConfigurations.cmake)
-  select_library_configurations(GLEW)
-endif ()
+if(GLEW_VERBOSE)
+  message(STATUS "FindGLEW: GLEW_INCLUDE_DIR: ${GLEW_INCLUDE_DIR}")
+  message(STATUS "FindGLEW: GLEW_INCLUDE_DIRS: ${GLEW_INCLUDE_DIRS}")
+endif()
+
+if("${CMAKE_GENERATOR_PLATFORM}" MATCHES "x64" OR "${CMAKE_GENERATOR}" MATCHES "Win64")
+  set(_arch "x64")
+else()
+  set(_arch "Win32")
+endif()
+
+
+__glew_set_find_library_suffix(SHARED)
+
+find_library(GLEW_SHARED_LIBRARY_RELEASE
+             NAMES GLEW glew glew32
+             PATH_SUFFIXES lib lib64 libx32 lib/Release/${_arch}
+             PATHS ENV GLEW_ROOT)
+
+find_library(GLEW_SHARED_LIBRARY_DEBUG
+             NAMES GLEWd glewd glew32d
+             PATH_SUFFIXES lib lib64
+             PATHS ENV GLEW_ROOT)
+
+
+__glew_set_find_library_suffix(STATIC)
+
+find_library(GLEW_STATIC_LIBRARY_RELEASE
+             NAMES GLEW glew glew32s
+             PATH_SUFFIXES lib lib64 libx32 lib/Release/${_arch}
+             PATHS ENV GLEW_ROOT)
+
+find_library(GLEW_STATIC_LIBRARY_DEBUG
+             NAMES GLEWds glewds glew32ds
+             PATH_SUFFIXES lib lib64
+             PATHS ENV GLEW_ROOT)
+
+include(${CMAKE_CURRENT_LIST_DIR}/SelectLibraryConfigurations.cmake)
+
+select_library_configurations(GLEW_SHARED)
+select_library_configurations(GLEW_STATIC)
+
+if(NOT GLEW_USE_STATIC_LIBS)
+  set(GLEW_LIBRARIES ${GLEW_SHARED_LIBRARY})
+else()
+  set(GLEW_LIBRARIES ${GLEW_STATIC_LIBRARY})
+endif()
+
+
+if(GLEW_VERBOSE)
+  message(STATUS "FindGLEW: GLEW_SHARED_LIBRARY_RELEASE: ${GLEW_SHARED_LIBRARY_RELEASE}")
+  message(STATUS "FindGLEW: GLEW_STATIC_LIBRARY_RELEASE: ${GLEW_STATIC_LIBRARY_RELEASE}")
+  message(STATUS "FindGLEW: GLEW_SHARED_LIBRARY_DEBUG: ${GLEW_SHARED_LIBRARY_DEBUG}")
+  message(STATUS "FindGLEW: GLEW_STATIC_LIBRARY_DEBUG: ${GLEW_STATIC_LIBRARY_DEBUG}")
+  message(STATUS "FindGLEW: GLEW_SHARED_LIBRARY: ${GLEW_SHARED_LIBRARY}")
+  message(STATUS "FindGLEW: GLEW_STATIC_LIBRARY: ${GLEW_STATIC_LIBRARY}")
+  message(STATUS "FindGLEW: GLEW_LIBRARIES: ${GLEW_LIBRARIES}")
+endif()
+
+
+# Read version from GL/glew.h file
+if(EXISTS "${GLEW_INCLUDE_DIR}/GL/glew.h")
+  file(STRINGS "${GLEW_INCLUDE_DIR}/GL/glew.h" _contents REGEX "^VERSION_.+ [0-9]+")
+  if(_contents)
+    string(REGEX REPLACE ".*VERSION_MAJOR[ \t]+([0-9]+).*" "\\1" GLEW_VERSION_MAJOR "${_contents}")
+    string(REGEX REPLACE ".*VERSION_MINOR[ \t]+([0-9]+).*" "\\1" GLEW_VERSION_MINOR "${_contents}")
+    string(REGEX REPLACE ".*VERSION_MICRO[ \t]+([0-9]+).*" "\\1" GLEW_VERSION_MICRO "${_contents}")
+    set(GLEW_VERSION "${GLEW_VERSION_MAJOR}.${GLEW_VERSION_MINOR}.${GLEW_VERSION_MICRO}")
+  endif()
+endif()
+
+if(GLEW_VERBOSE)
+  message(STATUS "FindGLEW: GLEW_VERSION_MAJOR: ${GLEW_VERSION_MAJOR}")
+  message(STATUS "FindGLEW: GLEW_VERSION_MINOR: ${GLEW_VERSION_MINOR}")
+  message(STATUS "FindGLEW: GLEW_VERSION_MICRO: ${GLEW_VERSION_MICRO}")
+  message(STATUS "FindGLEW: GLEW_VERSION: ${GLEW_VERSION}")
+endif()
 
-include(${CMAKE_CURRENT_LIST_DIR}/FindPackageHandleStandardArgs.cmake)
 find_package_handle_standard_args(GLEW
-                                  REQUIRED_VARS GLEW_INCLUDE_DIR GLEW_LIBRARY)
+                                  REQUIRED_VARS GLEW_INCLUDE_DIRS GLEW_LIBRARIES
+                                  VERSION_VAR GLEW_VERSION)
 
-if(GLEW_FOUND)
-  set(GLEW_INCLUDE_DIRS ${GLEW_INCLUDE_DIR})
+if(NOT GLEW_FOUND)
+  if(GLEW_VERBOSE)
+    message(STATUS "FindGLEW: could not found GLEW library.")
+  endif()
+  return()
+endif()
+
+
+if(NOT TARGET GLEW::glew AND NOT GLEW_USE_STATIC_LIBS)
+  if(GLEW_VERBOSE)
+    message(STATUS "FindGLEW: Creating GLEW::glew imported target.")
+  endif()
+
+  add_library(GLEW::glew UNKNOWN IMPORTED)
+
+  set_target_properties(GLEW::glew
+                        PROPERTIES INTERFACE_INCLUDE_DIRECTORIES "${GLEW_INCLUDE_DIRS}")
+
+  if(GLEW_SHARED_LIBRARY_RELEASE)
+    set_property(TARGET GLEW::glew
+                 APPEND
+                 PROPERTY IMPORTED_CONFIGURATIONS RELEASE)
+
+    set_target_properties(GLEW::glew
+                          PROPERTIES IMPORTED_LOCATION_RELEASE "${GLEW_SHARED_LIBRARY_RELEASE}")
+  endif()
+
+  if(GLEW_SHARED_LIBRARY_DEBUG)
+    set_property(TARGET GLEW::glew
+                 APPEND
+                 PROPERTY IMPORTED_CONFIGURATIONS DEBUG)
+
+    set_target_properties(GLEW::glew
+                          PROPERTIES IMPORTED_LOCATION_DEBUG "${GLEW_SHARED_LIBRARY_DEBUG}")
+  endif()
 
-  if(NOT GLEW_LIBRARIES)
-    set(GLEW_LIBRARIES ${GLEW_LIBRARY})
+elseif(NOT TARGET GLEW::glew_s AND GLEW_USE_STATIC_LIBS)
+  if(GLEW_VERBOSE)
+    message(STATUS "FindGLEW: Creating GLEW::glew_s imported target.")
   endif()
 
-  if (NOT TARGET GLEW::GLEW)
-    add_library(GLEW::GLEW UNKNOWN IMPORTED)
-    set_target_properties(GLEW::GLEW PROPERTIES
-      INTERFACE_INCLUDE_DIRECTORIES "${GLEW_INCLUDE_DIRS}")
+  add_library(GLEW::glew_s UNKNOWN IMPORTED)
 
-    if(GLEW_LIBRARY_RELEASE)
-      set_property(TARGET GLEW::GLEW APPEND PROPERTY IMPORTED_CONFIGURATIONS RELEASE)
-      set_target_properties(GLEW::GLEW PROPERTIES IMPORTED_LOCATION_RELEASE "${GLEW_LIBRARY_RELEASE}")
+  set_target_properties(GLEW::glew_s
+                        PROPERTIES INTERFACE_INCLUDE_DIRECTORIES "${GLEW_INCLUDE_DIRS}")
+
+  if(GLEW_STATIC_LIBRARY_RELEASE)
+    set_property(TARGET GLEW::glew_s
+                 APPEND
+                 PROPERTY IMPORTED_CONFIGURATIONS RELEASE)
+
+    set_target_properties(GLEW::glew_s
+                          PROPERTIES IMPORTED_LOCATION_RELEASE "${GLEW_STATIC_LIBRARY_RELEASE}")
+  endif()
+
+  if(GLEW_STATIC_LIBRARY_DEBUG)
+    set_property(TARGET GLEW::glew_s
+                 APPEND
+                 PROPERTY IMPORTED_CONFIGURATIONS DEBUG)
+
+    set_target_properties(GLEW::glew_s
+                          PROPERTIES IMPORTED_LOCATION_DEBUG "${GLEW_STATIC_LIBRARY_DEBUG}")
+  endif()
+endif()
+
+if(NOT TARGET GLEW::GLEW)
+  if(GLEW_VERBOSE)
+    message(STATUS "FindGLEW: Creating GLEW::GLEW imported target.")
+  endif()
+
+  add_library(GLEW::GLEW UNKNOWN IMPORTED)
+
+  set_target_properties(GLEW::GLEW
+                        PROPERTIES INTERFACE_INCLUDE_DIRECTORIES "${GLEW_INCLUDE_DIRS}")
+
+  if(TARGET GLEW::glew)
+    if(GLEW_SHARED_LIBRARY_RELEASE)
+      set_property(TARGET GLEW::GLEW
+                   APPEND
+                   PROPERTY IMPORTED_CONFIGURATIONS RELEASE)
+
+      set_target_properties(GLEW::GLEW
+                            PROPERTIES IMPORTED_LOCATION_RELEASE "${GLEW_SHARED_LIBRARY_RELEASE}")
+    endif()
+
+    if(GLEW_SHARED_LIBRARY_DEBUG)
+      set_property(TARGET GLEW::GLEW
+                   APPEND
+                   PROPERTY IMPORTED_CONFIGURATIONS DEBUG)
+
+      set_target_properties(GLEW::GLEW
+                            PROPERTIES IMPORTED_LOCATION_DEBUG "${GLEW_SHARED_LIBRARY_DEBUG}")
     endif()
 
-    if(GLEW_LIBRARY_DEBUG)
-      set_property(TARGET GLEW::GLEW APPEND PROPERTY IMPORTED_CONFIGURATIONS DEBUG)
-      set_target_properties(GLEW::GLEW PROPERTIES IMPORTED_LOCATION_DEBUG "${GLEW_LIBRARY_DEBUG}")
+  elseif(TARGET GLEW::glew_s)
+    if(GLEW_STATIC_LIBRARY_RELEASE)
+      set_property(TARGET GLEW::GLEW
+                   APPEND
+                   PROPERTY IMPORTED_CONFIGURATIONS RELEASE)
+
+      set_target_properties(GLEW::GLEW
+                            PROPERTIES IMPORTED_LOCATION_RELEASE "${GLEW_STATIC_LIBRARY_RELEASE}")
     endif()
 
-    if(NOT GLEW_LIBRARY_RELEASE AND NOT GLEW_LIBRARY_DEBUG)
-      set_property(TARGET GLEW::GLEW APPEND PROPERTY IMPORTED_LOCATION "${GLEW_LIBRARY}")
+    if(GLEW_STATIC_LIBRARY_DEBUG AND GLEW_USE_STATIC_LIBS)
+      set_property(TARGET GLEW::GLEW
+                   APPEND
+                   PROPERTY IMPORTED_CONFIGURATIONS DEBUG)
+
+      set_target_properties(GLEW::GLEW
+                            PROPERTIES IMPORTED_LOCATION_DEBUG "${GLEW_STATIC_LIBRARY_DEBUG}")
     endif()
+
+  elseif(GLEW_VERBOSE)
+    message(WARNING "FindGLEW: no `GLEW::glew` or `GLEW::glew_s` target was created. Something went wrong in FindGLEW target creation.")
   endif()
 endif()
-
-mark_as_advanced(GLEW_INCLUDE_DIR)