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, 98 insertions, 123 deletions

diff --git a/CMake/resources.cmake b/CMake/resources.cmake
index 4539f6f87..f5878e206 100644
--- a/CMake/resources.cmake
+++ b/CMake/resources.cmake
@@ -1,8 +1,8 @@
 #
-# Main CMakeLists.txt to build the FLTK project using CMake (www.cmake.org)
+# Resource definitions 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
@@ -19,38 +19,17 @@
 # check for headers, libraries and functions
 #######################################################################
 
-# The following code is work in progress (as of Feb 2018) - AlbrechtS
-
-# The cache option USE_FIND_FILE can be set to ON to switch back to the old
-# behavior that tries to find headers by find_file() which appears to be
-# error prone at least under Windows when MSYS2 and MinGW are both
-# installed on one system.
-# If USE_FIND_FILE is OFF (new behavior), then headers are searched for by
-# check_include_files() which tries to compile a small file to test if
-# the header file can be used. In some cases this needs more than one
-# header in a list because another header must be included before the
-# header being searched for.
-# Example: X11/Xlib.h must be included before X11/Xregion.h so Xregion.h
-# can be compiled successfully.
-
-# If CMAKE_REQUIRED_QUIET is 1 (default) the search is mostly quiet, if
-# it is 0 (or not defined) check_include_files() is more verbose and
-# the result of the search is logged with fl_debug_var().
+# If CMAKE_REQUIRED_QUIET is 1 (default) the search is mostly quiet,
+# if it is 0 (or not defined) check_include_files() is more verbose
+# and the result of the search is logged with fl_debug_var().
 # This is useful for debugging.
 
 set (CMAKE_REQUIRED_QUIET 1)
 
-include(CheckIncludeFiles)
-
-# The following macro is used to switch between old and new behavior.
-# Once this is stable (USE_FIND_FILE = 0) the unused part may be removed.
+include (CheckIncludeFiles)
 
 macro (fl_find_header VAR HEADER)
-  if (USE_FIND_FILE)
-    find_file (${VAR} "${HEADER}")
-  else (USE_FIND_FILE)
-    check_include_files("${HEADER}" ${VAR})
-  endif (USE_FIND_FILE)
+  check_include_files ("${HEADER}" ${VAR})
   if (NOT CMAKE_REQUIRED_QUIET)
     fl_debug_var (${VAR})
   endif (NOT CMAKE_REQUIRED_QUIET)
@@ -70,17 +49,12 @@ fl_find_header (HAVE_STRINGS_H strings.h)
 fl_find_header (HAVE_SYS_SELECT_H sys/select.h)
 fl_find_header (HAVE_SYS_STDTYPES_H sys/stdtypes.h)
 
-if (USE_FIND_FILE)
-  fl_find_header (HAVE_X11_XREGION_H "X11/Xregion.h")
-  fl_find_header (HAVE_XDBE_H "X11/extensions/Xdbe.h")
-else ()
-  fl_find_header (HAVE_X11_XREGION_H "X11/Xlib.h;X11/Xregion.h")
-  fl_find_header (HAVE_XDBE_H "X11/Xlib.h;X11/extensions/Xdbe.h")
-endif()
+fl_find_header (HAVE_X11_XREGION_H "X11/Xlib.h;X11/Xregion.h")
+fl_find_header (HAVE_XDBE_H "X11/Xlib.h;X11/extensions/Xdbe.h")
 
 if (WIN32 AND NOT CYGWIN)
   # we don't use pthreads on Windows (except for Cygwin, see options.cmake)
-  set(HAVE_PTHREAD_H 0)
+  set (HAVE_PTHREAD_H 0)
 else ()
   fl_find_header (HAVE_PTHREAD_H pthread.h)
 endif (WIN32 AND NOT CYGWIN)
@@ -111,20 +85,20 @@ if (MSVC)
   set (MSVC_RERUN_MESSAGE FALSE)
 
   if (NOT HAVE_GL_GLU_H)
-    message(STATUS "Warning: Header file GL/glu.h was not found.")
+    message (STATUS "Warning: Header file GL/glu.h was not found.")
     set (HAVE_GL_GLU_H 1)
     set (MSVC_RERUN_MESSAGE TRUE)
   endif (NOT HAVE_GL_GLU_H)
 
   if (NOT HAVE_LOCALE_H)
-    message(STATUS "Warning: Header file locale.h was not found.")
+    message (STATUS "Warning: Header file locale.h was not found.")
     set (HAVE_LOCALE_H 1)
     set (MSVC_RERUN_MESSAGE TRUE)
   endif (NOT HAVE_LOCALE_H)
 
   if (MSVC_RERUN_MESSAGE)
-    message(STATUS "The FLTK team recommends to rerun CMake from a")
-    message(STATUS "\"Developer Command Prompt for Visual Studio xxxx\"")
+    message (STATUS "The FLTK team recommends to rerun CMake from a")
+    message (STATUS "\"Developer Command Prompt for Visual Studio xxxx\"")
   endif (MSVC_RERUN_MESSAGE)
 
   unset (MSVC_RERUN_MESSAGE)
@@ -139,24 +113,25 @@ endif (MSVC)
 # once we found the first suitable header file.
 
 fl_find_header (HAVE_DIRENT_H dirent.h)
-if(NOT HAVE_DIRENT_H)
+
+if (NOT HAVE_DIRENT_H)
   fl_find_header (HAVE_SYS_NDIR_H sys/ndir.h)
-  if(NOT HAVE_SYS_NDIR_H)
+  if (NOT HAVE_SYS_NDIR_H)
     fl_find_header (HAVE_SYS_DIR_H sys/dir.h)
-    if(NOT HAVE_SYS_DIR_H)
+    if (NOT HAVE_SYS_DIR_H)
       fl_find_header (HAVE_NDIR_H ndir.h)
-    endif(NOT HAVE_SYS_DIR_H)
-  endif(NOT HAVE_SYS_NDIR_H)
-endif(NOT HAVE_DIRENT_H)
-
-mark_as_advanced(HAVE_ALSA_ASOUNDLIB_H HAVE_DIRENT_H HAVE_DLFCN_H)
-mark_as_advanced(HAVE_GL_GLU_H)
-mark_as_advanced(HAVE_LIBPNG_PNG_H HAVE_LOCALE_H HAVE_NDIR_H)
-mark_as_advanced(HAVE_OPENGL_GLU_H HAVE_PNG_H HAVE_PTHREAD_H)
-mark_as_advanced(HAVE_STDIO_H HAVE_STRINGS_H HAVE_SYS_DIR_H)
-mark_as_advanced(HAVE_SYS_NDIR_H HAVE_SYS_SELECT_H)
-mark_as_advanced(HAVE_SYS_STDTYPES_H HAVE_XDBE_H)
-mark_as_advanced(HAVE_X11_XREGION_H)
+    endif (NOT HAVE_SYS_DIR_H)
+  endif (NOT HAVE_SYS_NDIR_H)
+endif (NOT HAVE_DIRENT_H)
+
+mark_as_advanced (HAVE_ALSA_ASOUNDLIB_H HAVE_DIRENT_H HAVE_DLFCN_H)
+mark_as_advanced (HAVE_GL_GLU_H)
+mark_as_advanced (HAVE_LIBPNG_PNG_H HAVE_LOCALE_H HAVE_NDIR_H)
+mark_as_advanced (HAVE_OPENGL_GLU_H HAVE_PNG_H HAVE_PTHREAD_H)
+mark_as_advanced (HAVE_STDIO_H HAVE_STRINGS_H HAVE_SYS_DIR_H)
+mark_as_advanced (HAVE_SYS_NDIR_H HAVE_SYS_SELECT_H)
+mark_as_advanced (HAVE_SYS_STDTYPES_H HAVE_XDBE_H)
+mark_as_advanced (HAVE_X11_XREGION_H)
 
 #----------------------------------------------------------------------
 # The following code is used to find the include path for freetype
@@ -164,104 +139,104 @@ mark_as_advanced(HAVE_X11_XREGION_H)
 
 # where to find freetype headers
 
-find_path(FREETYPE_PATH freetype.h PATH_SUFFIXES freetype2)
-find_path(FREETYPE_PATH freetype/freetype.h PATH_SUFFIXES freetype2)
+find_path (FREETYPE_PATH freetype.h PATH_SUFFIXES freetype2)
+find_path (FREETYPE_PATH freetype/freetype.h PATH_SUFFIXES freetype2)
 
 if (FREETYPE_PATH)
-  include_directories(${FREETYPE_PATH})
+  include_directories (${FREETYPE_PATH})
 endif (FREETYPE_PATH)
 
-mark_as_advanced(FREETYPE_PATH)
+mark_as_advanced (FREETYPE_PATH)
 
 #######################################################################
 # libraries
-find_library(LIB_CAIRO cairo)
-find_library(LIB_dl dl)
-find_library(LIB_fontconfig fontconfig)
-find_library(LIB_freetype freetype)
-find_library(LIB_GL GL)
-find_library(LIB_MesaGL MesaGL)
-find_library(LIB_jpeg jpeg)
-find_library(LIB_png png)
-find_library(LIB_zlib z)
-
-mark_as_advanced(LIB_CAIRO LIB_dl LIB_fontconfig LIB_freetype)
-mark_as_advanced(LIB_GL LIB_MesaGL)
-mark_as_advanced(LIB_jpeg LIB_png LIB_zlib)
+find_library (LIB_CAIRO cairo)
+find_library (LIB_dl dl)
+find_library (LIB_fontconfig fontconfig)
+find_library (LIB_freetype freetype)
+find_library (LIB_GL GL)
+find_library (LIB_MesaGL MesaGL)
+find_library (LIB_jpeg jpeg)
+find_library (LIB_png png)
+find_library (LIB_zlib z)
+
+mark_as_advanced (LIB_CAIRO LIB_dl LIB_fontconfig LIB_freetype)
+mark_as_advanced (LIB_GL LIB_MesaGL)
+mark_as_advanced (LIB_jpeg LIB_png LIB_zlib)
 
 #######################################################################
 # functions
-include(CheckFunctionExists)
+include (CheckFunctionExists)
 
 # save CMAKE_REQUIRED_LIBRARIES (is this really necessary ?)
-if(DEFINED CMAKE_REQUIRED_LIBRARIES)
-  set(SAVED_REQUIRED_LIBRARIES ${CMAKE_REQUIRED_LIBRARIES})
-else(DEFINED CMAKE_REQUIRED_LIBRARIES)
-  unset(SAVED_REQUIRED_LIBRARIES)
-endif(DEFINED CMAKE_REQUIRED_LIBRARIES)
-set(CMAKE_REQUIRED_LIBRARIES)
+if (DEFINED CMAKE_REQUIRED_LIBRARIES)
+  set (SAVED_REQUIRED_LIBRARIES ${CMAKE_REQUIRED_LIBRARIES})
+else (DEFINED CMAKE_REQUIRED_LIBRARIES)
+  unset (SAVED_REQUIRED_LIBRARIES)
+endif (DEFINED CMAKE_REQUIRED_LIBRARIES)
+set (CMAKE_REQUIRED_LIBRARIES)
 
-if(HAVE_DLFCN_H)
-  set(HAVE_DLFCN_H 1)
-endif(HAVE_DLFCN_H)
+if (HAVE_DLFCN_H)
+  set (HAVE_DLFCN_H 1)
+endif (HAVE_DLFCN_H)
 
-set(CMAKE_REQUIRED_LIBRARIES ${CMAKE_DL_LIBS})
-CHECK_FUNCTION_EXISTS(dlsym                     HAVE_DLSYM)
-set(CMAKE_REQUIRED_LIBRARIES)
+set (CMAKE_REQUIRED_LIBRARIES ${CMAKE_DL_LIBS})
+CHECK_FUNCTION_EXISTS (dlsym                    HAVE_DLSYM)
+set (CMAKE_REQUIRED_LIBRARIES)
 
-CHECK_FUNCTION_EXISTS(localeconv                HAVE_LOCALECONV)
+CHECK_FUNCTION_EXISTS (localeconv               HAVE_LOCALECONV)
 
-if(LIB_png)
-  set(CMAKE_REQUIRED_LIBRARIES ${LIB_png})
-  CHECK_FUNCTION_EXISTS(png_get_valid           HAVE_PNG_GET_VALID)
-  CHECK_FUNCTION_EXISTS(png_set_tRNS_to_alpha   HAVE_PNG_SET_TRNS_TO_ALPHA)
-  set(CMAKE_REQUIRED_LIBRARIES)
-endif(LIB_png)
+if (LIB_png)
+  set (CMAKE_REQUIRED_LIBRARIES ${LIB_png})
+  CHECK_FUNCTION_EXISTS (png_get_valid          HAVE_PNG_GET_VALID)
+  CHECK_FUNCTION_EXISTS (png_set_tRNS_to_alpha  HAVE_PNG_SET_TRNS_TO_ALPHA)
+  set (CMAKE_REQUIRED_LIBRARIES)
+endif (LIB_png)
 
-CHECK_FUNCTION_EXISTS(scandir                   HAVE_SCANDIR)
-CHECK_FUNCTION_EXISTS(snprintf                  HAVE_SNPRINTF)
+CHECK_FUNCTION_EXISTS (scandir                  HAVE_SCANDIR)
+CHECK_FUNCTION_EXISTS (snprintf                 HAVE_SNPRINTF)
 
 # not really true but we convert strcasecmp calls to _stricmp calls in flstring.h
-if(MSVC)
-   set(HAVE_STRCASECMP 1)
-endif(MSVC)
+if (MSVC)
+   set (HAVE_STRCASECMP 1)
+endif (MSVC)
 
-CHECK_FUNCTION_EXISTS(strcasecmp                HAVE_STRCASECMP)
+CHECK_FUNCTION_EXISTS (strcasecmp               HAVE_STRCASECMP)
 
-CHECK_FUNCTION_EXISTS(strlcat                   HAVE_STRLCAT)
-CHECK_FUNCTION_EXISTS(strlcpy                   HAVE_STRLCPY)
-CHECK_FUNCTION_EXISTS(vsnprintf                 HAVE_VSNPRINTF)
+CHECK_FUNCTION_EXISTS (strlcat                  HAVE_STRLCAT)
+CHECK_FUNCTION_EXISTS (strlcpy                  HAVE_STRLCPY)
+CHECK_FUNCTION_EXISTS (vsnprintf                HAVE_VSNPRINTF)
 
-if(HAVE_SCANDIR AND NOT HAVE_SCANDIR_POSIX)
-   set(MSG "POSIX compatible scandir")
-   message(STATUS "Looking for ${MSG}")
+if (HAVE_SCANDIR AND NOT HAVE_SCANDIR_POSIX)
+   set (MSG "POSIX compatible scandir")
+   message (STATUS "Looking for ${MSG}")
    try_compile(V
       ${CMAKE_CURRENT_BINARY_DIR}
       ${CMAKE_CURRENT_SOURCE_DIR}/CMake/posixScandir.cxx
       )
-   if(V)
-      message(STATUS "${MSG} - found")
-      set(HAVE_SCANDIR_POSIX 1 CACHE INTERNAL "")
+   if (V)
+      message (STATUS "${MSG} - found")
+      set (HAVE_SCANDIR_POSIX 1 CACHE INTERNAL "")
    else()
-      message(STATUS "${MSG} - not found")
-      set(HAVE_SCANDIR_POSIX HAVE_SCANDIR_POSIX-NOTFOUND)
-   endif(V)
-endif(HAVE_SCANDIR AND NOT HAVE_SCANDIR_POSIX)
-mark_as_advanced(HAVE_SCANDIR_POSIX)
+      message (STATUS "${MSG} - not found")
+      set (HAVE_SCANDIR_POSIX HAVE_SCANDIR_POSIX-NOTFOUND)
+   endif (V)
+endif (HAVE_SCANDIR AND NOT HAVE_SCANDIR_POSIX)
+mark_as_advanced (HAVE_SCANDIR_POSIX)
 
 # restore CMAKE_REQUIRED_LIBRARIES (is this really necessary ?)
-if(DEFINED SAVED_REQUIRED_LIBRARIES)
-  set(CMAKE_REQUIRED_LIBRARIES ${SAVED_REQUIRED_LIBRARIES})
-  unset(SAVED_REQUIRED_LIBRARIES)
+if (DEFINED SAVED_REQUIRED_LIBRARIES)
+  set (CMAKE_REQUIRED_LIBRARIES ${SAVED_REQUIRED_LIBRARIES})
+  unset (SAVED_REQUIRED_LIBRARIES)
 else(DEFINED SAVED_REQUIRED_LIBRARIES)
-  unset(CMAKE_REQUIRED_LIBRARIES)
-endif(DEFINED SAVED_REQUIRED_LIBRARIES)
+  unset (CMAKE_REQUIRED_LIBRARIES)
+endif (DEFINED SAVED_REQUIRED_LIBRARIES)
 
 #######################################################################
 # packages
 
 # Doxygen: necessary for HTML and PDF docs
-find_package(Doxygen)
+find_package (Doxygen)
 
 # LaTex: necessary for PDF docs (note: FindLATEX doesn't return LATEX_FOUND)
 
@@ -270,15 +245,15 @@ find_package(Doxygen)
 
 set (LATEX_FOUND)
 if (DOXYGEN_FOUND)
-  find_package(LATEX)
+  find_package (LATEX)
   if (LATEX_COMPILER AND NOT LATEX_FOUND)
-    set(LATEX_FOUND YES)
+    set (LATEX_FOUND YES)
   endif (LATEX_COMPILER AND NOT LATEX_FOUND)
 endif (DOXYGEN_FOUND)
 
-# message("Doxygen  found : ${DOXYGEN_FOUND}")
-# message("LaTex    found : ${LATEX_FOUND}")
-# message("LaTex Compiler : ${LATEX_COMPILER}")
+# message ("Doxygen  found : ${DOXYGEN_FOUND}")
+# message ("LaTex    found : ${LATEX_FOUND}")
+# message ("LaTex Compiler : ${LATEX_COMPILER}")
 
 # Cleanup: unset local variables