CMake: refactor and reformat CMake files

- raise minimum CMake version from 2.6.3 to 3.2.3 (Jun 01, 2015)
- indent all CMake files according to the CMP (2 col.)
- refactor FLTK version number definitions and usage
- unify CMake and autoconf/configure variable names:
  - FL_VERSION -> FLTK_VERSION
  - FL_MAJOR_VERSION -> FLTK_VERSION_MAJOR
  - etc. for _MINOR_ and _PATCH_, respectively
  - note: this does not affect FL_VERSION etc. in source code
- generate "export headers" for all libraries (experimental: OFF)
- port some forgotten goodies from branch-1.3 to master
- merge and improve macro 'create_example' (WIP)
- remove "temporary" options and code for older CMake versions
- include and use 'GenerateExportHeader' (experimental, WIP: OFF)
  - note: created header files are not yet used
- build only *one* DLL with Visual Studio (tested, works)
  - similar to the bundled IDE projects in 1.3.x
- add some dynamically linked test/demo programs ('*-shared')
  if shared libraries are built (WIP)
- split 'macros.cmake': use one file per macro

1 files changed, 73 insertions, 65 deletions

diff --git a/CMake/export.cmake b/CMake/export.cmake
index d6c07564a..6e8bc5dd6 100644
--- a/CMake/export.cmake
+++ b/CMake/export.cmake
@@ -2,7 +2,7 @@
 # Main CMakeLists.txt to build the FLTK project using CMake (www.cmake.org)
 # Written by Michael Surette
 #
-# Copyright 1998-2018 by Bill Spitzak and others.
+# Copyright 1998-2020 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
@@ -18,104 +18,112 @@
 #######################################################################
 # final config and export
 #######################################################################
+
 # Set the fluid executable path
-if(CMAKE_CROSSCOMPILING)
-   find_file(FLUID_PATH
-      NAMES fluid fluid.exe
-      PATHS ENV PATH
-      NO_CMAKE_FIND_ROOT_PATH
-   )
-   add_executable(fluid IMPORTED)
-   set(FLTK_FLUID_EXECUTABLE ${FLUID_PATH})
-   set(FLUID)       # no export
-   set_target_properties(fluid
-      PROPERTIES IMPORTED_LOCATION ${FLUID_PATH}
-   )
-else()
-   add_subdirectory(fluid)
-   set(FLTK_FLUID_EXECUTABLE fluid)
-   set(FLUID fluid) # export
-endif(CMAKE_CROSSCOMPILING)
+if (CMAKE_CROSSCOMPILING)
+  find_file(FLUID_PATH
+    NAMES fluid fluid.exe
+    PATHS ENV PATH
+    NO_CMAKE_FIND_ROOT_PATH
+  )
+  add_executable(fluid IMPORTED)
+  set (FLTK_FLUID_EXECUTABLE ${FLUID_PATH})
+  set (FLUID)       # no export
+  set_target_properties(fluid
+    PROPERTIES IMPORTED_LOCATION ${FLUID_PATH}
+  )
+else ()
+  add_subdirectory(fluid)
+  set (FLTK_FLUID_EXECUTABLE fluid)
+  set (FLUID fluid) # export
+endif (CMAKE_CROSSCOMPILING)
 
 add_subdirectory(src)
 
 # generate FLTK-Targets.cmake for build directory use
 export(TARGETS ${FLUID} ${FLTK_LIBRARIES} FILE ${CMAKE_CURRENT_BINARY_DIR}/FLTK-Targets.cmake)
 
+# generate FLTK-Functions.cmake for build directory use
+configure_file (
+  ${CMAKE_CURRENT_SOURCE_DIR}/CMake/FLTK-Functions.cmake
+  ${CMAKE_CURRENT_BINARY_DIR}/FLTK-Functions.cmake
+  COPYONLY
+)
+
 # generate FLTKConfig.cmake for build directory use
-set(INCLUDE_DIRS "${FLTK_INCLUDE_DIRS}")
-set(CONFIG_PATH ${CMAKE_CURRENT_BINARY_DIR})
+set (INCLUDE_DIRS "${FLTK_INCLUDE_DIRS}")
+set (CONFIG_PATH ${CMAKE_CURRENT_BINARY_DIR})
 
 configure_file(
-   ${CMAKE_CURRENT_SOURCE_DIR}/CMake/FLTKConfig.cmake.in
-   ${CMAKE_CURRENT_BINARY_DIR}/FLTKConfig.cmake
-   @ONLY
+  ${CMAKE_CURRENT_SOURCE_DIR}/CMake/FLTKConfig.cmake.in
+  ${CMAKE_CURRENT_BINARY_DIR}/FLTKConfig.cmake
+  @ONLY
 )
 
 # generate UseFLTK.cmake for build directory use
 configure_file(
-   ${CMAKE_CURRENT_SOURCE_DIR}/CMake/UseFLTK.cmake.in
-   ${CMAKE_CURRENT_BINARY_DIR}/UseFLTK.cmake
-   @ONLY
+  ${CMAKE_CURRENT_SOURCE_DIR}/CMake/UseFLTK.cmake.in
+  ${CMAKE_CURRENT_BINARY_DIR}/UseFLTK.cmake
+  @ONLY
 )
 
 # generate fltk-config for build directory use
-set(prefix ${CMAKE_CURRENT_BINARY_DIR})
-set(exec_prefix "\${prefix}")
-set(includedir "${CMAKE_CURRENT_SOURCE_DIR}")
-set(BINARY_DIR "${CMAKE_CURRENT_BINARY_DIR}")
-set(libdir "\${exec_prefix}/lib")
-set(srcdir ".")
+set (prefix ${CMAKE_CURRENT_BINARY_DIR})
+set (exec_prefix "\${prefix}")
+set (includedir "${CMAKE_CURRENT_SOURCE_DIR}")
+set (BINARY_DIR "${CMAKE_CURRENT_BINARY_DIR}")
+set (libdir "\${exec_prefix}/lib")
+set (srcdir ".")
 
-set(LIBNAME "${libdir}/libfltk.a")
+set (LIBNAME "${libdir}/libfltk.a")
 
 configure_file(
-   "${CMAKE_CURRENT_SOURCE_DIR}/fltk-config.in"
-   "${CMAKE_CURRENT_BINARY_DIR}/fltk-config"
-   @ONLY
+  "${CMAKE_CURRENT_SOURCE_DIR}/fltk-config.in"
+  "${CMAKE_CURRENT_BINARY_DIR}/fltk-config"
+  @ONLY
 )
 
 if (UNIX)
   execute_process(COMMAND chmod 755 fltk-config
-                  WORKING_DIRECTORY "${CMAKE_CURRENT_BINARY_DIR}"
+    WORKING_DIRECTORY "${CMAKE_CURRENT_BINARY_DIR}"
   )
 endif (UNIX)
 
 # prepare some variables for config.h
 
-if(IS_ABSOLUTE "${FLTK_DATADIR}")
-  set(PREFIX_DATA "${FLTK_DATADIR}/fltk")
-else(IS_ABSOLUTE "${FLTK_DATADIR}")
-  set(PREFIX_DATA "${CMAKE_INSTALL_PREFIX}/${FLTK_DATADIR}/fltk")
-endif(IS_ABSOLUTE "${FLTK_DATADIR}")
+if (IS_ABSOLUTE "${FLTK_DATADIR}")
+  set (PREFIX_DATA "${FLTK_DATADIR}/fltk")
+else (IS_ABSOLUTE "${FLTK_DATADIR}")
+  set (PREFIX_DATA "${CMAKE_INSTALL_PREFIX}/${FLTK_DATADIR}/fltk")
+endif (IS_ABSOLUTE "${FLTK_DATADIR}")
 
-if(IS_ABSOLUTE "${FLTK_DOCDIR}")
-  set(PREFIX_DOC "${FLTK_DOCDIR}/fltk")
-else(IS_ABSOLUTE "${FLTK_DOCDIR}")
-  set(PREFIX_DOC "${CMAKE_INSTALL_PREFIX}/${FLTK_DOCDIR}/fltk")
-endif(IS_ABSOLUTE "${FLTK_DOCDIR}")
+if (IS_ABSOLUTE "${FLTK_DOCDIR}")
+  set (PREFIX_DOC "${FLTK_DOCDIR}/fltk")
+else (IS_ABSOLUTE "${FLTK_DOCDIR}")
+  set (PREFIX_DOC "${CMAKE_INSTALL_PREFIX}/${FLTK_DOCDIR}/fltk")
+endif (IS_ABSOLUTE "${FLTK_DOCDIR}")
 
-set(CONFIG_H_IN configh.cmake.in)
-set(CONFIG_H config.h)
+set (CONFIG_H_IN configh.cmake.in)
+set (CONFIG_H config.h)
 
 # generate config.h
 
 configure_file(
-   "${CMAKE_CURRENT_SOURCE_DIR}/${CONFIG_H_IN}"
-   "${CMAKE_CURRENT_BINARY_DIR}/${CONFIG_H}"
-   @ONLY
+  "${CMAKE_CURRENT_SOURCE_DIR}/${CONFIG_H_IN}"
+  "${CMAKE_CURRENT_BINARY_DIR}/${CONFIG_H}"
+  @ONLY
 )
 
-if(OPTION_CREATE_LINKS)
-   # Set PREFIX_INCLUDE to the proper value.
-   if(IS_ABSOLUTE ${FLTK_INCLUDEDIR})
-      set(PREFIX_INCLUDE ${FLTK_INCLUDEDIR})
-   else()
-      set(PREFIX_INCLUDE "${CMAKE_INSTALL_PREFIX}/${FLTK_INCLUDEDIR}")
-   endif(IS_ABSOLUTE ${FLTK_INCLUDEDIR})
-   configure_file(
-      "${CMAKE_CURRENT_SOURCE_DIR}/CMake/install-symlinks.cmake.in"
-      "${CMAKE_CURRENT_BINARY_DIR}/install-symlinks.cmake"
-      @ONLY
-   )
-endif(OPTION_CREATE_LINKS)
+if (OPTION_CREATE_LINKS)
+  # Set PREFIX_INCLUDE to the proper value.
+  if (IS_ABSOLUTE ${FLTK_INCLUDEDIR})
+    set (PREFIX_INCLUDE ${FLTK_INCLUDEDIR})
+  else ()
+    set (PREFIX_INCLUDE "${CMAKE_INSTALL_PREFIX}/${FLTK_INCLUDEDIR}")
+  endif (IS_ABSOLUTE ${FLTK_INCLUDEDIR})
+  configure_file(
+    "${CMAKE_CURRENT_SOURCE_DIR}/CMake/install-symlinks.cmake.in"
+    "${CMAKE_CURRENT_BINARY_DIR}/install-symlinks.cmake"
+    @ONLY
+  )
+endif (OPTION_CREATE_LINKS)