Harmonize and document syntax of config.h source files

- configh.in: add and improve comments, reorder statements
- configh.cmake.in: add comments, fix whitespace

- src/drivers/GDI/Fl_GDI_Graphics_Driver_line_style.cxx:
  fix trailing whitespace

1 files changed, 23 insertions, 4 deletions

diff --git a/configh.in b/configh.in
index 3ef98ebae..f43d24142 100644
--- a/configh.in
+++ b/configh.in
@@ -1,7 +1,7 @@
 /*
  * Configuration file for the Fast Light Tool Kit (FLTK).
  *
- * Copyright 1998-2016 by Bill Spitzak and others.
+ * Copyright 1998-2021 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
@@ -15,6 +15,18 @@
  */
 
 /*
+ * Note: configure syntax vs. CMake syntax in source files (examples):
+ *
+ *   configh.in               configh.cmake.in
+ *   ---------------------    ----------------------------
+ *   #define HAVE_GL 0        #cmakedefine01 HAVE_GL
+ *   #undef HAVE_SNPRINTF     #cmakedefine HAVE_SNPRINTF 1
+ *
+ *   The former #define's the given macro either as 0 or 1,
+ *   the latter either does not define the macro or #define's it as 1.
+ */
+
+/*
  * Where to find files...
  */
 
@@ -168,7 +180,7 @@
  * USE_SDL
  *
  * Should we use SDL for the current platform
- * *FIXME* Not yet implemented in configure !
+ * *FIXME* USE_SDL not yet implemented in configure !
  *
  */
 
@@ -285,7 +297,6 @@
 #undef HAVE_LIBPNG
 #undef HAVE_LIBZ
 #undef HAVE_LIBJPEG
-#undef FLTK_USE_SVG
 
 /*
  * FLTK_USE_CAIRO
@@ -319,6 +330,14 @@
 #undef HAVE_PNG_SET_TRNS_TO_ALPHA
 
 /*
+* FLTK_USE_SVG
+*
+* Do we want FLTK to read and write SVG-formatted files ?
+*/
+
+#undef FLTK_USE_SVG
+
+/*
  * Do we have POSIX threading?
  */
 
@@ -368,7 +387,7 @@
 
 /*
  * Do we want filename handling and a filechooser?
- * *FIXME* Not yet implemented in configure !
+ * *FIXME* FL_CFG_NO_FILESYSTEM_SUPPORT not yet implemented in configure !
  */
 
 #undef FL_CFG_NO_FILESYSTEM_SUPPORT