CMake: Improve configuration summary, add fl_debug_pkg macro

fl_debug_pkg(...) can be used to display CMake variables set by
  executing pkg_check_modules(). This is for CMake debugging only.

The CMake configuration summary displays configuration options
  of Wayland, Pango, Xft, and Cairo configuration.

CMake/fl_debug_pkg.cmake

@@ -0,0 +1,63 @@
+#
+# Macro used by the CMake build system for the Fast Light Tool Kit (FLTK).
+#
+# Copyright 2022 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
+# file is missing or damaged, see the license at:
+#
+#     https://www.fltk.org/COPYING.php
+#
+# Please see the following page on how to report bugs and issues:
+#
+#     https://www.fltk.org/bugs.php
+#
+
+#######################################################################
+# fl_debug_pkg - a macro to output pkgconfig debugging info
+#######################################################################
+#
+# This macro displays the name and value of some CMake variables
+# defined by pkg_check_modules().
+#
+# Syntax:
+#
+#   fl_debug_pkg(PREFIX NAME)
+#
+# Example for package "cairo":
+#
+#  pkg_check_modules (CAIRO cairo)
+#  fl_debug_pkg (CAIRO cairo)
+#
+# The first command searches for pkg 'cairo' and stores the results
+# in CMake variables with prefix 'CAIRO_'.
+#
+# The second command displays all relevant variables if the package has
+# been found, otherwise only 'CAIRO_FOUND' (empty or false).
+#
+#######################################################################
+
+macro (fl_debug_pkg PREFIX NAME)
+  message("")
+  message(STATUS "Results of pkg_check_modules(${PREFIX}, ${NAME}):")
+  fl_debug_var (${PREFIX}_FOUND)
+  if (${PREFIX}_FOUND)
+
+    fl_debug_var (${PREFIX}_LIBRARIES)
+    fl_debug_var (${PREFIX}_LINK_LIBRARIES)
+    fl_debug_var (${PREFIX}_LIBRARY_DIRS)
+    fl_debug_var (${PREFIX}_LDFLAGS)
+    fl_debug_var (${PREFIX}_LDFLAGS_OTHER)
+    fl_debug_var (${PREFIX}_INCLUDE_DIRS)
+    fl_debug_var (${PREFIX}_CFLAGS)
+    fl_debug_var (${PREFIX}_CFLAGS_OTHER)
+
+    fl_debug_var (${PREFIX}_VERSION)
+    fl_debug_var (${PREFIX}_PREFIX)
+    fl_debug_var (${PREFIX}_INCLUDEDIR)
+    fl_debug_var (${PREFIX}_LIBDIR)
+
+  endif ()
+  message("")
+endmacro (fl_debug_pkg)

CMake/fl_debug_var.cmake

@@ -1,8 +1,7 @@
 #
 # Macro used by the CMake build system for the Fast Light Tool Kit (FLTK).
-# Written by Michael Surette
 #
-# Copyright 1998-2020 by Bill Spitzak and others.
+# Copyright 1998-2022 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

CMakeLists.txt

@@ -48,6 +48,7 @@ project (FLTK VERSION 1.4.0)
 #######################################################################
 
 include (CMake/fl_debug_var.cmake)
+include (CMake/fl_debug_pkg.cmake)
 include (CMake/fl_add_library.cmake)
 include (CMake/compatibility.cmake)
 
@@ -237,5 +238,34 @@ else ()
   message (STATUS "                 ZLIB = System")
 endif ()
 
+if (UNIX)
+
+  if (OPTION_USE_WAYLAND)
+    message (STATUS "Use Wayland:     Yes")
+  else ()
+    message (STATUS "Use Wayland:     No")
+  endif ()
+
+  if (USE_PANGO)
+    message (STATUS "Use Pango:       Yes")
+  else (USE_PANGO)
+    message (STATUS "Use Pango:       No")
+    if (USE_XFT)
+      message (STATUS "Use Xft:         Yes")
+    else ()
+      message (STATUS "Use Xft:         No")
+    endif (USE_XFT)
+  endif (USE_PANGO)
+
+endif (UNIX)
+
+if (FLTK_HAVE_CAIROEXT)
+  message (STATUS "Cairo support:   Yes (extended)")
+elseif (FLTK_HAVE_CAIRO)
+  message (STATUS "Cairo support:   Yes (standard)")
+else ()
+  message (STATUS "Cairo support:   No")
+endif ()
+
 message ("")
 message (STATUS "End of Configuration Summary --\n")