Add support for detection and processing of clean program termination request.

The default handling of cmd-Q/Quit program under MacOS was to terminate the
program if all its windows are closed without returning from FLTK's event loop.
This was running against a strong design feature of FLTK that programs
should always complete their event loop and return from main() when cleanly
terminating.

In the new code for the MacOS platform, cmd-Q/Quit program no longer terminates
the program. Instead, the event loop is interrupted and a call to Fl::program_should_quit()
allows to detect that program termination has been requested, if necessary.

git-svn-id: file:///fltk/svn/fltk/branches/branch-1.4@12647 ea41ed52-d2ee-0310-a9c1-e6b18d33e121

CHANGES

@@ -18,6 +18,12 @@ Changes in FLTK 1.4.0					Released: ??? ?? 2017
   New Features and Extensions
 
   - (add new items here)
+  - New member functions FL::run_also_windowless(),
+    and FL::wait_also_windowless(double secnds) to run the event
+    loop even without any mapped window if the platform supports it.
+  - New member functions Fl::program_should_quit(void),
+    and Fl::program_should_quit(int) to support detection by the library
+    of a request to terminate cleanly the program.
   - MacOS platform: Added support for rescaling the GUI of any app at run-time
     using the command/+/-/0/ keystrokes.
   - MSWindows platform: Added optional support for rescaling the GUI of any app

FL/Fl.H

@@ -259,6 +259,7 @@ public:
 private:  
   static unsigned char options_[OPTION_LAST];
   static unsigned char options_read_;
+  static int program_should_quit_; // non-zero means the program was asked to cleanly terminate
 
 public:  
   /*
@@ -412,6 +413,19 @@ public:
   static int check();
   static int ready();
   static int run();
+  static int run_also_windowless();
+  static int wait_also_windowless(double delay = 1e20);
+  /** Returns non-zero when a request for program termination was received and accepted.
+   On the MacOS platform, the "Quit xxx" item of the application menu is such a request,
+   that is considered accepted when all windows are closed. On other platforms, this function
+   returns 0 until \p Fl::program_should_quit(1) is called.
+   */
+  static int program_should_quit() {return program_should_quit_;}
+  /** Indicate to the FLTK library whether a program termination request was received and accepted.
+  A program may set this to 1, for example, while performing a platform-independent command asking the program to cleanly
+  terminate, similarly to the "Quit xxx" item of the application menu under MacOS. */
+  static void program_should_quit(int should_i) { program_should_quit_ = should_i; }
+
   static Fl_Widget* readqueue();
   /**
   Adds a one-shot timeout callback.  The function will be called by

FL/Fl_System_Driver.H

@@ -4,7 +4,7 @@
 // A base class for platform specific system calls
 // for the Fast Light Tool Kit (FLTK).
 //
-// Copyright 2010-2017 by Bill Spitzak and others.
+// Copyright 2010-2018 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
@@ -225,6 +225,9 @@ public:
   virtual const char *meta_name() { return "Meta"; }
   virtual const char *alt_name() { return "Alt"; }
   virtual const char *control_name() { return "Ctrl"; }
+  // The default implementation of the next 2 functions may be enough.
+  virtual int run_also_windowless();
+  virtual int wait_also_windowless(double delay);
 };
 
 #endif // FL_SYSTEM_DRIVER_H

src/Fl.cxx

@@ -589,6 +589,22 @@ int Fl::ready()
   return screen_driver()->ready();
 }
 
+/** Run the event loop even without any mapped window if the platform supports it.
+ \return zero indicates the event loop has been terminated.
+ */
+int Fl::run_also_windowless() {
+  return Fl::system_driver()->run_also_windowless();
+}
+
+/** Wait for \p delay seconds or until an event occurs, even without any mapped window if the platform supports it.
+ \return non zero indicates the event loop should be terminated
+ */
+int Fl::wait_also_windowless(double delay) {
+  return Fl::system_driver()->wait_also_windowless(delay);
+}
+
+int Fl::program_should_quit_ = 0;
+
 ////////////////////////////////////////////////////////////////
 // Window list management:
 

src/Fl_System_Driver.cxx

@@ -445,6 +445,15 @@ void Fl_System_Driver::gettime(time_t *sec, int *usec) {
   *usec = 0;
 }
 
+int Fl_System_Driver::run_also_windowless() {
+  return Fl::run();
+}
+
+int Fl_System_Driver::wait_also_windowless(double delay) {
+  Fl::wait(delay);
+  return Fl::first_window() != NULL;
+}
+
 //
 // End of "$Id$".
 //

src/Fl_cocoa.mm

@@ -1507,6 +1507,7 @@ static FLWindowDelegate *flwindowdelegate_instance = nil;
 - (void)applicationWillUnhide:(NSNotification *)notify;
 - (BOOL)application:(NSApplication *)theApplication openFile:(NSString *)filename;
 @end
+
 @implementation FLAppDelegate
 - (void)applicationDidFinishLaunching:(NSNotification *)notification
 {
@@ -1515,19 +1516,21 @@ static FLWindowDelegate *flwindowdelegate_instance = nil;
 - (NSApplicationTerminateReply)applicationShouldTerminate:(NSApplication*)sender
 {
   fl_lock_function();
-  NSApplicationTerminateReply reply = NSTerminateNow;
   while ( Fl_X::first ) {
     Fl_Window *win = Fl::first_window();
     if (win->parent()) win = win->top_window();
     Fl_Widget_Tracker wt(win); // track the window object
     Fl::handle(FL_CLOSE, win);
     if (wt.exists() && win->shown()) { // the user didn't close win
-      reply = NSTerminateCancel; // so we return to the main program now
       break;
     }
   }
   fl_unlock_function();
-  return reply;
+  if ( ! Fl::first_window() ) {
+    Fl::program_should_quit(1);
+    breakMacEventLoop(); // necessary when called through menu and in Fl::wait()
+  }
+  return NSTerminateCancel;
 }
 - (void)applicationDidBecomeActive:(NSNotification *)notify
 {
@@ -1716,6 +1719,18 @@ static void drain_dropped_files_list() {
   free(fname);
 }
 
+int Fl_Darwin_System_Driver::run_also_windowless() {
+  while (!Fl::program_should_quit()) {
+    Fl::wait(1e20);
+  }
+  return 0;
+}
+
+int Fl_Darwin_System_Driver::wait_also_windowless(double delay) {
+  if (!Fl::program_should_quit()) Fl::wait(delay);
+  return !Fl::program_should_quit();
+}
+
 /*
  * Install an open documents event handler...
  */

src/drivers/Darwin/Fl_Darwin_System_Driver.H

@@ -4,7 +4,7 @@
 // Definition of Apple Darwin system driver
 // for the Fast Light Tool Kit (FLTK).
 //
-// Copyright 2010-2016 by Bill Spitzak and others.
+// Copyright 2010-2018 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
@@ -81,6 +81,8 @@ public:
   virtual const char *meta_name();
   virtual const char *alt_name();
   virtual const char *control_name();
+  virtual int run_also_windowless();
+  virtual int wait_also_windowless(double delay);
 };
 
 #endif // FL_DARWIN_SYSTEM_DRIVER_H