Fixing and upgrading Fl_Preferences (#374)

* Added filename function to Fl_Preferences

Static function to get filename before opening.
Member to get filename after opening.
Bug fixes for memory mapped preferences.

* ERROR is a macro on Windows, don't use it

* Added Fl_Preferences::dirty().

User can now check if the database will be written
when flushed or destroyed.
Flush returns a crude error code.

* Fl_Preferences::get binary data returns # of bytes read.

* Verified group deletion code

* Fl_Preferences ignores locale.

This will make .prefs files interchangeable
between different computers.

* Updating the Preferences Mode to ignore locale.

* Fixes in docs.

FL/Fl_Preferences.H

@@ -1,7 +1,7 @@
 //
 // Preferences implementation for the Fast Light Tool Kit (FLTK).
 //
-// Copyright 2002-2010 by Matthias Melcher.
+// Copyright 2002-2022 by Matthias Melcher.
 //
 // 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
@@ -24,31 +24,74 @@
 #  include "Fl_Export.H"
 
 /**
-   \brief Fl_Preferences provides methods to store user
-   settings between application starts.
+ \brief Fl_Preferences store user settings between application starts.
 
-   It is similar to the
-   Registry on Windows and Preferences on MacOS, and provides a
-   simple configuration mechanism for UNIX.
+ Fl_Preferences are similar to the Registry on Windows and Preferences on MacOS,
+ providing a simple method to store customisable user settings between app
+ launches, i.e. the previous window position or a history of previously
+ used documents.
 
-   Fl_Preferences uses a hierarchy to store data. It
-   bundles similar data into groups and manages entries in these
-   groups as name/value pairs.
+ Preferences are organized in a hierarchy of groups. Every group can contain
+ more groups and any number of kay/value pairs. Keys can be text strings
+ containing ASCII letters, digits, periods, and underscores. Forward slashes
+ in a key name are treated as subgroups, i.e the key 'window/width' would
+ actually refere to the key 'width' inside the group 'window'.
 
-   Preferences are stored in text files that can be edited
-   manually. The file format is easy to read and relatively
-   forgiving. Preferences files are the same on all platforms. User
-   comments in preference files are preserved. Filenames are unique
-   for each application by using a vendor/application naming
-   scheme. The user must provide default values for all entries to
-   ensure proper operation should preferences be corrupted or not
-   yet exist.
+ Keys have usually a unique name within their group. Duplicate kays are
+ possible though and can beaccessed using the index based functions.
 
-   Entries can be of any length. However, the size of each
-   preferences file should be kept small for performance
-   reasons. One application can have multiple preferences files.
-   Extensive binary data however should be stored in separate
-   files: see \a Fl_Preferences::getUserdataPath() .
+ A value should be an ASCII string. Control characters and utf8 sequences are
+ stores as octal values. Long strings will wrap at the line ending and will be
+ reassembled when reading the file back.
+
+ Many shortcuts exist to set and get numerical values and binary data.
+
+ Preferences are stored in text files that can be edited manually if needed.
+ The file format is easy to read and relatively forgiving. Preferences files
+ are the same on all platforms. User comments in preference files are preserved.
+ Filenames are unique for each application by using a vendor/application naming
+ scheme. The user must provide default values for all entries to ensure proper
+ operation should preferences be corrupted or not yet exist.
+
+ FLTK preferences are not meant to replace a fully features database. No merging
+ of data takes place. If several instances of an app access the same database at
+ the same time, only the most recent changes will persist.
+
+ Preferences should no be used to store document data. The .prefs file should
+ be kept small for performance reasons. One application can have multiple
+ preferences files. Extensive binary data however should be stored in separate
+ files: see \a Fl_Preferences::getUserdataPath() .
+
+ Fl_Preferences are not thread-safe. They can temprorarily change the locale
+ on some platforms during read an write access, which is alse observable in
+ other threads of the same app.
+
+ Typically a preferences database is read at startup and close, and then writte
+ again at app shutdown:
+ ```.cpp
+ int appWindowWidth, appWindowHeight;
+ void launch() {
+   Fl_Preferences app(Fl_Preferences::USER_L, "matthiasm.com", "hello");
+   // 'app' constructor will be called, reading data from .prefs file
+   Fl_Preferences window(app, "window");
+   window.get("width", appWindowWidth, 800);
+   window.get("height", appWindowHeight, 600);
+   // 'app' destructor will be called, writing data to .prefs file
+ }
+ void quit() {
+   Fl_Preferences app(Fl_Preferences::USER_L, "matthiasm.com", "hello");
+   Fl_Preferences window(app, "window");
+   window.set("width", appWindowWidth);
+   window.set("height", appWindowHeight);
+ }
+ ```
+
+ \see Fl_Preferences::Fl_Preferences( Root root, const char *vendor, const char *application )
+
+ As a special case, Fl_Preferences can be memeory mapped and not be associated
+ with a file on disk.
+
+ \see Fl_Preferences::Fl_Preferences( Fl_Preferences *parent, const char *group )
 
    \note Starting with FLTK 1.3, preference databases are expected to
      be in UTF-8 encoding. Previous databases were stored in the
@@ -59,6 +102,14 @@
      the preferences files has changed slightly. Please see
      Fl_Preferences::Fl_Preferences(Root, const char*, const char*)
      for details.
+
+   \note Starting with FLTK 1.4, preference files should be created with
+     `SYSTEM_L` or `USER_L` to be interchangeable between computers with
+     differing loacale settings. The legacy modes, `LOCAL` and `SYSTEM`, will
+     read and write floating point values using the decimal point of the
+     current locale. As a result, a fp-value would be writte '3,1415' on a
+     German machine, and would be read back as '3.0' on a US machine because
+     the comma would not be recoginized as an alternative decimal point.
  */
 class FL_EXPORT Fl_Preferences {
 
@@ -67,12 +118,17 @@ public:
      Define the scope of the preferences.
    */
   enum Root {
-    SYSTEM = 0,        ///< Preferences are used system-wide
-    USER,              ///< Preferences apply only to the current user
+    UNKNOWN_ROOT_TYPE = -1, ///< Returned if storage could not be determined.
+    SYSTEM = 0,        ///< Preferences are used system-wide, deprecated, see SYSTEM_L
+    USER,              ///< Preferences apply only to the current user, deprecated, see USER_L
+    MEMORY,            ///< Returned if querying runtime prefs
     ROOT_MASK = 0xFF,  ///< masks for the values above
     CORE = 0x100,      ///< OR'd by FLTK to read and write core library preferences and options
     CORE_SYSTEM = CORE|SYSTEM,
-    CORE_USER = CORE|USER
+    CORE_USER = CORE|USER,
+    C_LOCALE = 0x1000, ///< this flag should always be set, it makes sure that floating point values wre writte correctly independently of the current locale
+    SYSTEM_L = SYSTEM|C_LOCALE, ///< Preferences are used system-wide
+    USER_L = USER|C_LOCALE,     ///< Preferences apply only to the current user
   };
 
   /**
@@ -120,6 +176,7 @@ public:
 
   static void file_access(unsigned int flags);
   static unsigned int file_access();
+  static Root filename( char *buffer, size_t buffer_size, Root root, const char *vendor, const char *application );
 
   Fl_Preferences( Root root, const char *vendor, const char *application );
   Fl_Preferences( const char *path, const char *vendor, const char *application );
@@ -131,6 +188,8 @@ public:
   Fl_Preferences( ID id );
   virtual ~Fl_Preferences();
 
+  Root filename( char *buffer, size_t buffer_size);
+
   /** Return an ID that can later be reused to open more references to this dataset.
    */
   ID id() { return (ID)node; }
@@ -176,12 +235,15 @@ public:
   char get( const char *entry, char *value,   const char *defaultValue, int maxSize );
   char get( const char *entry, void *&value,  const void *defaultValue, int defaultSize );
   char get( const char *entry, void *value,   const void *defaultValue, int defaultSize, int maxSize );
+  char get( const char *entry, void *value,   const void *defaultValue, int defaultSize, int *size );
 
   int size( const char *entry );
 
   char getUserdataPath( char *path, int pathlen );
 
-  void flush();
+  int flush();
+
+  int dirty();
 
   // char export( const char *filename, Type fileFormat );
   // char import( const char *filename );
@@ -233,10 +295,10 @@ public:  // older Sun compilers need this (public definition of the following cl
 
   class FL_EXPORT Node {        // a node contains a list to all its entries
                                 // and all means to manage the tree structure
-    Node *child_, *next_;
+    Node *first_child_, *next_;
     union {                     // these two are mutually exclusive
       Node *parent_;            // top_ bit clear
-      RootNode *root_;          // top_ bit set
+      RootNode *root_node_;          // top_ bit set
     };
     char *path_;
     Entry *entry_;
@@ -265,7 +327,7 @@ public:  // older Sun compilers need this (public definition of the following cl
     Node *addChild( const char *path );
     void setParent( Node *parent );
     Node *parent() { return top_?0L:parent_; }
-    void setRoot(RootNode *r) { root_ = r; top_ = 1; }
+    void setRoot(RootNode *r) { root_node_ = r; top_ = 1; }
     RootNode *findRoot();
     char remove();
     char dirty();
@@ -290,7 +352,7 @@ public:  // older Sun compilers need this (public definition of the following cl
     Fl_Preferences *prefs_;
     char *filename_;
     char *vendor_, *application_;
-    Root root_;
+    Root root_type_;
   public:
     RootNode( Fl_Preferences *, Root root, const char *vendor, const char *application );
     RootNode( Fl_Preferences *, const char *path, const char *vendor, const char *application );
@@ -299,6 +361,8 @@ public:  // older Sun compilers need this (public definition of the following cl
     int read();
     int write();
     char getPath( char *path, int pathlen );
+    char *filename() { return filename_; }
+    Root root() { return root_type_; }
   };
   friend class RootNode;
 

fluid/Fl_Function_Type.cxx

@@ -1530,7 +1530,7 @@ static void load_comments_preset(Fl_Preferences &menu) {
     "FLTK/Header" };
   int i;
   menu.set("n", 5);
-  Fl_Preferences db(Fl_Preferences::USER, "fltk.org", "fluid_comments");
+  Fl_Preferences db(Fl_Preferences::USER_L, "fltk.org", "fluid_comments");
   for (i=0; i<5; i++) {
     menu.set(Fl_Preferences::Name(i), predefined_comment[i]);
     db.set(predefined_comment[i], comment_text[i]);
@@ -1545,7 +1545,7 @@ void Fl_Comment_Type::open() {
   const char *text = name();
   {
     int i=0, n=0;
-    Fl_Preferences menu(Fl_Preferences::USER, "fltk.org", "fluid_comments_menu");
+    Fl_Preferences menu(Fl_Preferences::USER_L, "fltk.org", "fluid_comments_menu");
     comment_predefined->clear();
     comment_predefined->add("_Edit/Add current comment...");
     comment_predefined->add("_Edit/Remove last selection...");
@@ -1583,9 +1583,9 @@ void Fl_Comment_Type::open() {
             char *name = fl_strdup(xname);
             for (char*s=name;*s;s++) if (*s==':') *s = ';';
             int n;
-            Fl_Preferences db(Fl_Preferences::USER, "fltk.org", "fluid_comments");
+            Fl_Preferences db(Fl_Preferences::USER_L, "fltk.org", "fluid_comments");
             db.set(name, comment_input->buffer()->text());
-            Fl_Preferences menu(Fl_Preferences::USER, "fltk.org", "fluid_comments_menu");
+            Fl_Preferences menu(Fl_Preferences::USER_L, "fltk.org", "fluid_comments_menu");
             menu.get("n", n, 0);
             menu.set(Fl_Preferences::Name(n), name);
             menu.set("n", ++n);
@@ -1599,10 +1599,10 @@ void Fl_Comment_Type::open() {
           } else if (fl_choice("Are you sure that you want to delete the entry\n"
                                "\"%s\"\nfrom the database?", "Cancel", "Delete",
                                NULL, itempath)) {
-            Fl_Preferences db(Fl_Preferences::USER, "fltk.org", "fluid_comments");
+            Fl_Preferences db(Fl_Preferences::USER_L, "fltk.org", "fluid_comments");
             db.deleteEntry(itempath);
             comment_predefined->remove(last_selected_item);
-            Fl_Preferences menu(Fl_Preferences::USER, "fltk.org", "fluid_comments_menu");
+            Fl_Preferences menu(Fl_Preferences::USER_L, "fltk.org", "fluid_comments_menu");
             int i, n;
             for (i=4, n=0; i<comment_predefined->size(); i++) {
               const Fl_Menu_Item *mi = comment_predefined->menu()+i;
@@ -1617,7 +1617,7 @@ void Fl_Comment_Type::open() {
           // load the selected comment from the database
           if (comment_predefined->item_pathname(itempath, 255)==0) {
             if (itempath[0]=='/') memmove(itempath, itempath+1, 255);
-            Fl_Preferences db(Fl_Preferences::USER, "fltk.org", "fluid_comments");
+            Fl_Preferences db(Fl_Preferences::USER_L, "fltk.org", "fluid_comments");
             char *text;
             db.get(itempath, text, "(no text found in data base)");
             comment_input->buffer()->text(text);

fluid/alignment_panel.fl

@@ -1,5 +1,10 @@
 # data file for the Fltk User Interface Designer (fluid)
 version 1.0400
+i18n_type 1
+i18n_include {<libintl.h>}
+i18n_conditional FLTK_GETTEXT_FOUND
+i18n_function gettext
+i18n_static_function gettext_noop
 header_name {.h}
 code_name {.cxx}
 comment {//
@@ -35,7 +40,7 @@ decl {\#include <FL/Fl_Text_Buffer.H>} {public local
 decl {\#include <FL/Fl_Text_Display.H>} {public local
 }
 
-decl {\#include <FL/filename.H>} {selected public local
+decl {\#include <FL/filename.H>} {public local
 }
 
 decl {\#include <FL/Fl_Preferences.H>} {private global
@@ -323,7 +328,7 @@ Function {make_shell_window()} {open
         tooltip {save the design to the .fl file before running the command} xywh {82 39 136 19} down_box DOWN_BOX labelsize 12
       }
       Fl_Check_Button shell_writecode_button {
-        label {save source code}
+        label {save source code} selected
         tooltip {generate the source code and header file before running the command} xywh {82 59 120 19} down_box DOWN_BOX labelsize 12
       }
       Fl_Check_Button shell_writemsgs_button {
@@ -524,11 +529,11 @@ wShowZoomFactor->value(opt[Fl::OPTION_SHOW_SCALING][mode]);} {}
 }
 
 Function {readPrefs()} {
-  comment {read all preferences and refresh the GUI} private return_type void
+  comment {read all preferences and refresh the GUI} open private return_type void
 } {
   code {// read all preferences and refresh the GUI
 {
-  Fl_Preferences prefs(Fl_Preferences::SYSTEM, "fltk.org", "fltk");
+  Fl_Preferences prefs(Fl_Preferences::SYSTEM_L, "fltk.org", "fltk");
   Fl_Preferences opt_prefs(prefs, "options");
   opt_prefs.get("ArrowFocus", opt[Fl::OPTION_ARROW_FOCUS][1], 2);
   opt_prefs.get("VisibleFocus", opt[Fl::OPTION_VISIBLE_FOCUS][1], 2);
@@ -539,7 +544,7 @@ Function {readPrefs()} {
   opt_prefs.get("ShowZoomFactor", opt[Fl::OPTION_SHOW_SCALING ][1], 2);
 }
 {
-  Fl_Preferences prefs(Fl_Preferences::USER, "fltk.org", "fltk");
+  Fl_Preferences prefs(Fl_Preferences::USER_L, "fltk.org", "fltk");
   Fl_Preferences opt_prefs(prefs, "options");
   opt_prefs.get("ArrowFocus", opt[Fl::OPTION_ARROW_FOCUS][0], 2);
   opt_prefs.get("VisibleFocus", opt[Fl::OPTION_VISIBLE_FOCUS][0], 2);
@@ -553,11 +558,11 @@ refreshUI();} {}
 }
 
 Function {writePrefs()} {
-  comment {write all preferences using the array} private return_type void
+  comment {write all preferences using the array} open private return_type void
 } {
   code {// write all preferences using the array
 {
-  Fl_Preferences prefs(Fl_Preferences::SYSTEM, "fltk.org", "fltk");
+  Fl_Preferences prefs(Fl_Preferences::SYSTEM_L, "fltk.org", "fltk");
   Fl_Preferences opt_prefs(prefs, "options");
   if (opt[Fl::OPTION_ARROW_FOCUS][1]==2) opt_prefs.deleteEntry("ArrowFocus");
   else opt_prefs.set("ArrowFocus", opt[Fl::OPTION_ARROW_FOCUS][1]);
@@ -575,7 +580,7 @@ Function {writePrefs()} {
   else opt_prefs.set("ShowZoomFactor", opt[Fl::OPTION_SHOW_SCALING][1]);
 }
 {
-  Fl_Preferences prefs(Fl_Preferences::USER, "fltk.org", "fltk");
+  Fl_Preferences prefs(Fl_Preferences::USER_L, "fltk.org", "fltk");
   Fl_Preferences opt_prefs(prefs, "options");
   if (opt[Fl::OPTION_ARROW_FOCUS][0]==2) opt_prefs.deleteEntry("ArrowFocus");
   else opt_prefs.set("ArrowFocus", opt[Fl::OPTION_ARROW_FOCUS][0]);
@@ -594,7 +599,7 @@ Function {writePrefs()} {
 }} {}
 }
 
-Function {show_global_settings_window()} {return_type void
+Function {show_global_settings_window()} {open return_type void
 } {
   code {if (!global_settings_window)
   make_global_settings_window();

fluid/fluid.cxx

@@ -72,7 +72,7 @@ Fl_Menu_Bar *main_menubar = NULL;
 Fl_Window *main_window;
 
 /// Fluid application preferences, allways accessible, will be flushed when app closes.
-Fl_Preferences  fluid_prefs(Fl_Preferences::USER, "fltk.org", "fluid");
+Fl_Preferences  fluid_prefs(Fl_Preferences::USER_L, "fltk.org", "fluid");
 
 /// Align widget position and size when designing, saved in app preferences and project file.
 int gridx = 5;

src/Fl_System_Driver.H

@@ -128,6 +128,8 @@ public:
   virtual unsigned utf8from_mb(char* dst, unsigned dstlen, const char* src, unsigned srclen);
   // implement to shield fprintf() from locale changes in decimal point
   virtual int clocale_printf(FILE *output, const char *format, va_list args);
+  virtual int clocale_snprintf(char *output, size_t output_size, const char *format, va_list args);
+  virtual int clocale_sscanf(const char *input, const char *format, va_list args);
   // implement functions telling whether a key is pressed
   virtual int event_key(int) {return 0;}
   virtual int get_key(int) {return 0;}

src/Fl_System_Driver.cxx

@@ -404,6 +404,14 @@ int Fl_System_Driver::clocale_printf(FILE *output, const char *format, va_list a
   return vfprintf(output, format, args);
 }
 
+int Fl_System_Driver::clocale_snprintf(char *output, size_t output_size, const char *format, va_list args) {
+  return vsnprintf(output, output_size, format, args);
+}
+
+int Fl_System_Driver::clocale_sscanf(const char *input, const char *format, va_list args) {
+  return vsscanf(input, format, args);
+}
+
 int Fl_System_Driver::filename_expand(char *to,int tolen, const char *from) {
   char *temp = new char[tolen];
   strlcpy(temp,from, tolen);

src/Fl_cocoa.mm

@@ -4528,7 +4528,10 @@ int Fl_Darwin_System_Driver::calc_mac_os_version() {
   return fl_mac_os_version;
 }
 
-char *Fl_Darwin_System_Driver::preference_rootnode(Fl_Preferences *prefs, Fl_Preferences::Root root,
+/*
+ Note: `prefs` can be NULL!
+ */
+char *Fl_Darwin_System_Driver::preference_rootnode(Fl_Preferences * /*prefs*/, Fl_Preferences::Root root,
                                                    const char *vendor, const char *application)
 {
   static char *filename = 0L;

src/drivers/Android/Fl_Android_System_Driver.H

@@ -69,6 +69,8 @@ public:
   virtual unsigned utf8to_mb(const char *src, unsigned srclen, char *dst, unsigned dstlen);
   virtual unsigned utf8from_mb(char *dst, unsigned dstlen, const char *src, unsigned srclen);
   virtual int clocale_printf(FILE *output, const char *format, va_list args);
+  virtual int clocale_snprintf(char *output, size_t output_size, const char *format, va_list args);
+  virtual int clocale_sscanf(const char *input, const char *format, va_list args);
   // these 2 are in Fl_get_key_win32.cxx
   virtual int event_key(int k);
   virtual int get_key(int k);

src/drivers/Android/Fl_Android_System_Driver.cxx

@@ -487,6 +487,14 @@ int Fl_WinAPI_System_Driver::clocale_printf(FILE *output, const char *format, va
   return retval;
 }
 
+int Fl_WinAPI_System_Driver::clocale_snprintf(char *output, size_t output_size, const char *format, va_list args) {
+  //... write me
+}
+
+int Fl_WinAPI_System_Driver::clocale_sscanf(const char *input, const char *format, va_list args) {
+  //... write me
+}
+
 int Fl_WinAPI_System_Driver::filename_list(const char *d, dirent ***list,
                                            int (*sort)(struct dirent **, struct dirent **),
                                            char *errmsg, int errmsg_sz ) {
@@ -834,6 +842,9 @@ void Fl_WinAPI_System_Driver::newUUID(char *uuidBuffer)
   }
 }
 
+/*
+ Note: `prefs` can be NULL!
+ */
 char *Fl_WinAPI_System_Driver::preference_rootnode(Fl_Preferences *prefs, Fl_Preferences::Root root, const char *vendor,
                                                   const char *application)
 {

src/drivers/Darwin/Fl_Darwin_System_Driver.H

@@ -45,6 +45,8 @@ public:
   virtual int single_arg(const char *arg);
   virtual int arg_and_value(const char *name, const char *value);
   virtual int clocale_printf(FILE *output, const char *format, va_list args);
+  virtual int clocale_snprintf(char *output, size_t output_size, const char *format, va_list args);
+  virtual int clocale_sscanf(const char *input, const char *format, va_list args);
   static void *get_carbon_function(const char *name);
   static int calc_mac_os_version(); // computes the fl_mac_os_version global variable
   static unsigned short *compute_macKeyLookUp();

src/drivers/Darwin/Fl_Darwin_System_Driver.cxx

@@ -116,10 +116,15 @@ int Fl_Darwin_System_Driver::arg_and_value(const char *name, const char *value)
   return strcmp(name, "NSDocumentRevisionsDebugMode") == 0;
 }
 
+#if MAC_OS_X_VERSION_MAX_ALLOWED >= MAC_OS_X_VERSION_10_4
+static locale_t postscript_locale = NULL;
+#endif
+
 int Fl_Darwin_System_Driver::clocale_printf(FILE *output, const char *format, va_list args) {
 #if MAC_OS_X_VERSION_MAX_ALLOWED >= MAC_OS_X_VERSION_10_4
   if (fl_mac_os_version >= 100400) {
-    static locale_t postscript_locale = newlocale(LC_NUMERIC_MASK, "C", (locale_t)0);
+    if (!postscript_locale)
+      postscript_locale = newlocale(LC_NUMERIC_MASK, "C", (locale_t)0);
     return vfprintf_l(output, postscript_locale, format, args);
   }
 #endif
@@ -130,6 +135,37 @@ int Fl_Darwin_System_Driver::clocale_printf(FILE *output, const char *format, va
   return retval;
 }
 
+int Fl_Darwin_System_Driver::clocale_snprintf(char *output, size_t output_size, const char *format, va_list args) {
+#if MAC_OS_X_VERSION_MAX_ALLOWED >= MAC_OS_X_VERSION_10_4
+  if (fl_mac_os_version >= 100400) {
+    if (!postscript_locale)
+      postscript_locale = newlocale(LC_NUMERIC_MASK, "C", (locale_t)0);
+    return vsnprintf_l(output, output_size, postscript_locale, format, args);
+  }
+#endif
+  char *saved_locale = setlocale(LC_NUMERIC, NULL);
+  setlocale(LC_NUMERIC, "C");
+  int retval = vsnprintf(output, output_size, format, args);
+  setlocale(LC_NUMERIC, saved_locale);
+  return retval;
+}
+
+int Fl_Darwin_System_Driver::clocale_sscanf(const char *input, const char *format, va_list args) {
+#if MAC_OS_X_VERSION_MAX_ALLOWED >= MAC_OS_X_VERSION_10_4
+  if (fl_mac_os_version >= 100400) {
+    if (!postscript_locale)
+      postscript_locale = newlocale(LC_NUMERIC_MASK, "C", (locale_t)0);
+    return vsscanf_l(input, postscript_locale, format, args);
+  }
+#endif
+  char *saved_locale = setlocale(LC_NUMERIC, NULL);
+  setlocale(LC_NUMERIC, "C");
+  int retval = vsscanf(input, format, args);
+  setlocale(LC_NUMERIC, saved_locale);
+  return retval;
+}
+
+
 /* Returns the address of a Carbon function after dynamically loading the Carbon library if needed.
  Supports old Mac OS X versions that may use a couple of Carbon calls:
  GetKeys used by OS X 10.3 or before (in Fl::get_key())

src/drivers/WinAPI/Fl_WinAPI_System_Driver.H

@@ -67,6 +67,8 @@ public:
   virtual unsigned utf8to_mb(const char *src, unsigned srclen, char *dst, unsigned dstlen);
   virtual unsigned utf8from_mb(char *dst, unsigned dstlen, const char *src, unsigned srclen);
   virtual int clocale_printf(FILE *output, const char *format, va_list args);
+  virtual int clocale_snprintf(char *output, size_t output_size, const char *format, va_list args);
+  virtual int clocale_sscanf(const char *input, const char *format, va_list args);
   // these 2 are in Fl_get_key_win32.cxx
   virtual int event_key(int k);
   virtual int get_key(int k);

src/drivers/WinAPI/Fl_WinAPI_System_Driver.cxx

@@ -455,9 +455,14 @@ unsigned Fl_WinAPI_System_Driver::utf8from_mb(char *dst, unsigned dstlen, const
   return ret;
 }
 
+#if defined(_MSC_VER) && (_MSC_VER >= 1400 /*Visual Studio 2005*/)
+static _locale_t c_locale = NULL;
+#endif
+
 int Fl_WinAPI_System_Driver::clocale_printf(FILE *output, const char *format, va_list args) {
 #if defined(_MSC_VER) && (_MSC_VER >= 1400 /*Visual Studio 2005*/)
-  static _locale_t c_locale = _create_locale(LC_NUMERIC, "C");
+  if (!c_locale)
+    c_locale = _create_locale(LC_NUMERIC, "C");
   int retval = _vfprintf_l(output, format, c_locale, args);
 #else
   char *saved_locale = setlocale(LC_NUMERIC, NULL);
@@ -468,6 +473,35 @@ int Fl_WinAPI_System_Driver::clocale_printf(FILE *output, const char *format, va
   return retval;
 }
 
+int Fl_WinAPI_System_Driver::clocale_snprintf(char *output, size_t output_size, const char *format, va_list args) {
+#if defined(_MSC_VER) && (_MSC_VER >= 1400 /*Visual Studio 2005*/)
+  if (!c_locale)
+    c_locale = _create_locale(LC_NUMERIC, "C");
+  int retval = _vsnprintf_l(output, output_size, format, c_locale, args);
+#else
+  char *saved_locale = setlocale(LC_NUMERIC, NULL);
+  setlocale(LC_NUMERIC, "C");
+  int retval = vsnprintf(output, output_size, format, args);
+  setlocale(LC_NUMERIC, saved_locale);
+#endif
+  return retval;
+}
+
+int Fl_WinAPI_System_Driver::clocale_sscanf(const char *input, const char *format, va_list args) {
+#if defined(_MSC_VER) && (_MSC_VER >= 1400 /*Visual Studio 2005*/)
+  if (!c_locale)
+    c_locale = _create_locale(LC_NUMERIC, "C");
+  int retval = _vsscanf_l(input, format, c_locale, args);
+#else
+  char *saved_locale = setlocale(LC_NUMERIC, NULL);
+  setlocale(LC_NUMERIC, "C");
+  int retval = vsscanf(input, format, args);
+  setlocale(LC_NUMERIC, saved_locale);
+#endif
+  return retval;
+}
+
+
 int Fl_WinAPI_System_Driver::filename_list(const char *d, dirent ***list,
                                            int (*sort)(struct dirent **, struct dirent **),
                                            char *errmsg, int errmsg_sz) {
@@ -814,7 +848,10 @@ void Fl_WinAPI_System_Driver::newUUID(char *uuidBuffer)
   }
 }
 
-char *Fl_WinAPI_System_Driver::preference_rootnode(Fl_Preferences *prefs, Fl_Preferences::Root root, const char *vendor,
+/*
+ Note: `prefs` can be NULL!
+ */
+char *Fl_WinAPI_System_Driver::preference_rootnode(Fl_Preferences * /*prefs*/, Fl_Preferences::Root root, const char *vendor,
                                                   const char *application)
 {
 #  define FLPREFS_RESOURCE      "Software\\Microsoft\\Windows\\CurrentVersion\\Explorer\\Shell Folders"

src/drivers/X11/Fl_X11_System_Driver.H

@@ -31,6 +31,8 @@ public:
   virtual void display_arg(const char *arg);
   virtual int XParseGeometry(const char*, int*, int*, unsigned int*, unsigned int*);
   virtual int clocale_printf(FILE *output, const char *format, va_list args);
+  virtual int clocale_snprintf(char *output, size_t output_size, const char *format, va_list args);
+  virtual int clocale_sscanf(const char *input, const char *format, va_list args);
   // these 2 are in Fl_get_key.cxx
   virtual int event_key(int k);
   virtual int get_key(int k);

src/drivers/X11/Fl_X11_System_Driver.cxx

@@ -79,10 +79,15 @@ Fl_System_Driver *Fl_System_Driver::newSystemDriver()
   return new Fl_X11_System_Driver();
 }
 
+#if defined(__linux__) && defined(_XOPEN_SOURCE) && _XOPEN_SOURCE >= 700
+static locale_t c_locale = NULL;
+#endif
+
 
 int Fl_X11_System_Driver::clocale_printf(FILE *output, const char *format, va_list args) {
 #if defined(__linux__) && defined(_XOPEN_SOURCE) && _XOPEN_SOURCE >= 700
-  static locale_t c_locale = newlocale(LC_NUMERIC_MASK, "C", duplocale(LC_GLOBAL_LOCALE));
+  if (!c_locale)
+    c_locale = newlocale(LC_NUMERIC_MASK, "C", duplocale(LC_GLOBAL_LOCALE));
   locale_t previous_locale = uselocale(c_locale);
   int retval = vfprintf(output, format, args);
   uselocale(previous_locale);
@@ -95,6 +100,35 @@ int Fl_X11_System_Driver::clocale_printf(FILE *output, const char *format, va_li
   return retval;
 }
 
+int Fl_X11_System_Driver::clocale_snprintf(char *output, size_t output_size, const char *format, va_list args) {
+#if defined(__linux__) && defined(_XOPEN_SOURCE) && _XOPEN_SOURCE >= 700
+  if (!c_locale)
+    c_locale = newlocale(LC_NUMERIC_MASK, "C", duplocale(LC_GLOBAL_LOCALE));
+  locale_t previous_locale = uselocale(c_locale);
+  int retval = vsnprintf(output, output_size, format, args);
+  uselocale(previous_locale);
+#else
+  char *saved_locale = setlocale(LC_NUMERIC, NULL);
+  setlocale(LC_NUMERIC, "C");
+  int retval = vsnprintf(output, output_size, format, args);
+  setlocale(LC_NUMERIC, saved_locale);
+#endif
+}
+
+int Fl_X11_System_Driver::clocale_sscanf(const char *input, const char *format, va_list args) {
+#if defined(__linux__) && defined(_XOPEN_SOURCE) && _XOPEN_SOURCE >= 700
+  if (!c_locale)
+    c_locale = newlocale(LC_NUMERIC_MASK, "C", duplocale(LC_GLOBAL_LOCALE));
+  locale_t previous_locale = uselocale(c_locale);
+  int retval = vsscanf(input, format, args);
+  uselocale(previous_locale);
+#else
+  char *saved_locale = setlocale(LC_NUMERIC, NULL);
+  setlocale(LC_NUMERIC, "C");
+  int retval = vsscanf(input, format, args);
+  setlocale(LC_NUMERIC, saved_locale);
+#endif
+}
 
 // Find a program in the path...
 static char *path_find(const char *program, char *filename, int filesize) {
@@ -415,7 +449,10 @@ void Fl_X11_System_Driver::newUUID(char *uuidBuffer)
           b[8], b[9], b[10], b[11], b[12], b[13], b[14], b[15]);
 }
 
-char *Fl_X11_System_Driver::preference_rootnode(Fl_Preferences *prefs, Fl_Preferences::Root root, const char *vendor,
+/*
+ Note: `prefs` can be NULL!
+ */
+char *Fl_X11_System_Driver::preference_rootnode(Fl_Preferences * /*prefs*/, Fl_Preferences::Root root, const char *vendor,
                                                 const char *application)
 {
   static char *filename = 0L;

test/blocks.cxx

@@ -497,7 +497,7 @@ class BlockWindow : public Fl_Double_Window {
 };
 
 
-Fl_Preferences  BlockWindow::prefs_(Fl_Preferences::USER, "fltk.org", "blocks");
+Fl_Preferences  BlockWindow::prefs_(Fl_Preferences::USER_L, "fltk.org", "blocks");
 
 
 int main(int argc, char *argv[]) {

test/preferences.fl

@@ -45,7 +45,7 @@ Function {saveAndCloseWindowCB( Fl_Widget*, void* )} {open private return_type v
 Fl::delete_widget(myWindow);} {}
 }
 
-Function {} {open return_type int
+Function {} {open selected return_type int
 } {
   Fl_Window myWindow {
     label {My Preferences}
@@ -78,7 +78,7 @@ Function {} {open return_type int
           xywh {0 0 100 20}
         }
         MenuItem {} {
-          label {p.m.} selected
+          label {p.m.}
           xywh {0 0 100 20}
         }
       }
@@ -206,10 +206,32 @@ int intValue;
 char buffer[80];
 double doubleValue;
 
-Fl_Preferences app( Fl_Preferences::USER, project, application );
+char path[ FL_PATH_MAX ];
+Fl_Preferences::Root root = 
+  Fl_Preferences::filename(path, FL_PATH_MAX, Fl_Preferences::USER_L, project, application);
+if (root == Fl_Preferences::UNKNOWN_ROOT_TYPE) {
+  printf("Location of future Preferences file not found.\\n");
+} else {
+  printf("Preferences file will be located at:\\n%s\\n", path);
+}
 
-  char path[ FL_PATH_MAX ];
-  app.getUserdataPath( path, sizeof(path) );
+Fl_Preferences app( Fl_Preferences::USER_L, project, application );
+
+  root = app.filename(path, FL_PATH_MAX);
+  if (root == Fl_Preferences::UNKNOWN_ROOT_TYPE) {
+    printf("Location of app Preferences file not found.\\n");
+  } else if (root == Fl_Preferences::MEMORY) {
+    printf("App Preferences are memory mapped.\\n");
+  } else {
+    printf("App Preferences file is actually located at:\\n%s\\n", path);
+  }
+  
+  app.getUserdataPath( path, sizeof(path) );  
+  if (path[0]) {
+    printf("Preferences user data directory is located at:\\n%s\\n", path);
+  } else {
+    printf("Location of Preferences user data directory not found.\\n");
+  }
 
   Fl_Preferences bed( app, "Bed" );
     bed.get( "alarm", buffer, "8:00", 79 );
@@ -278,7 +300,7 @@ Fl_Preferences app( Fl_Preferences::USER, project, application );
 
 Function {writePrefs()} {open return_type void
 } {
-  code {Fl_Preferences app( Fl_Preferences::USER, project, application );
+  code {Fl_Preferences app( Fl_Preferences::USER_L, project, application );
 
   Fl_Preferences bed( app, "Bed" );
 

test/sudoku.cxx

@@ -625,7 +625,7 @@ SudokuCell::handle(int event) {
 
 // Sudoku class globals...
 Fl_Help_Dialog  *Sudoku::help_dialog_ = (Fl_Help_Dialog *)0;
-Fl_Preferences  Sudoku::prefs_(Fl_Preferences::USER, "fltk.org", "sudoku");
+Fl_Preferences  Sudoku::prefs_(Fl_Preferences::USER_L, "fltk.org", "sudoku");
 
 
 // Create a Sudoku game window...