CMake: Raise cmake_minimum_required from 3.12 to 3.15

Remove code that checks CMake versions lower than 3.15

4 files changed, 13 insertions, 19 deletions

diff --git a/CMake/compatibility.cmake b/CMake/compatibility.cmake
index 338e9b9e3..233b4001f 100644
--- a/CMake/compatibility.cmake
+++ b/CMake/compatibility.cmake
@@ -1,7 +1,7 @@
 #
 # CMake compatibility functions and macros for the Fast Light Tool Kit (FLTK)
 #
-# Copyright 1998-2021 by Bill Spitzak and others.
+# Copyright 1998-2023 by Bill Spitzak and others.
 #
 # This library is free software. Distribution and use rights are outlined in
 # the file "COPYING" which should have been included with this file.  If this
@@ -16,7 +16,7 @@
 
 ################################################################################
 #
-# The functions (and macros) in this file are defined to simplify CMake
+# The functions and maybe macros in this file are defined to simplify CMake
 # code that uses features not available in all supported CMake versions.
 # Functions should be preferred (rather than macros) because functions
 # have their own variable scope.
@@ -33,6 +33,12 @@
 #
 ################################################################################
 
+
+# Right now we don't need compatibility functions
+# This file is currently "empty" but left for documentation purposes
+# An example function documentation follows...
+
+
 ################################################################################
 #
 # function fl_target_link_directories - add link directories to target
@@ -62,13 +68,3 @@
 #   can be an empty list.
 #
 ################################################################################
-
-function (fl_target_link_directories TARGET SCOPE DIRS)
-
-  if (CMAKE_VERSION VERSION_LESS "3.13")
-    link_directories (${DIRS})
-  else ()
-    target_link_directories (${TARGET} ${SCOPE} ${DIRS})
-  endif ()
-
-endfunction () # fl_target_link_directories()
diff --git a/CMake/fl_create_example.cmake b/CMake/fl_create_example.cmake
index 77fb24d0b..1ff85d17c 100644
--- a/CMake/fl_create_example.cmake
+++ b/CMake/fl_create_example.cmake
@@ -125,7 +125,7 @@ function (CREATE_EXAMPLE NAME SOURCES LIBRARIES)
   endif ()
 
   if (FLTK_HAVE_CAIRO AND PKG_CAIRO_LIBRARY_DIRS)
-    fl_target_link_directories (${TARGET_NAME} PUBLIC ${PKG_CAIRO_LIBRARY_DIRS})
+    target_link_directories (${TARGET_NAME} PUBLIC ${PKG_CAIRO_LIBRARY_DIRS})
   endif ()
 
   if (USE_GDIPLUS)        # can only be true on Windows
diff --git a/CMake/options.cmake b/CMake/options.cmake
index 9f3079595..6e2443cfb 100644
--- a/CMake/options.cmake
+++ b/CMake/options.cmake
@@ -536,7 +536,7 @@ if (OPTION_USE_GL)
     unset(HAVE_GL_GLU_H CACHE)
     find_file (HAVE_GL_GLU_H GL/glu.h PATHS ${X11_INCLUDE_DIR})
   else()
-    include (FindOpenGL)
+    find_package(OpenGL)
     if (APPLE)
       set (HAVE_GL_GLU_H ${HAVE_OPENGL_GLU_H})
     endif (APPLE)
diff --git a/CMake/setup.cmake b/CMake/setup.cmake
index 1ff5585ce..7dd91ebd4 100644
--- a/CMake/setup.cmake
+++ b/CMake/setup.cmake
@@ -82,11 +82,9 @@ include(TestBigEndian)
 TEST_BIG_ENDIAN(WORDS_BIGENDIAN)
 
 if (CMAKE_GENERATOR MATCHES "Xcode")
-  if (NOT (CMAKE_VERSION VERSION_LESS 3.9)) # CMake 3.9 and up
-    # Tell Xcode to regenerate scheme information automatically whenever the
-    # CMake configuration changes without asking the user
-    set (CMAKE_XCODE_GENERATE_SCHEME 1)
-  endif()
+  # Tell Xcode to regenerate scheme information automatically whenever the
+  # CMake configuration changes without asking the user
+  set (CMAKE_XCODE_GENERATE_SCHEME 1)
 endif()
 
 if (APPLE)