Adds default shortcut to Fl_Shortcut_Button.

FL/Fl_Shortcut_Button.H

@@ -21,8 +21,9 @@
 
 class FL_EXPORT Fl_Shortcut_Button : public Fl_Button {
 private:
-  bool hot_, pre_hot_;
+  bool hot_, pre_hot_, default_set_, handle_default_button_;
   Fl_Shortcut pre_esc_;
+  Fl_Shortcut default_shortcut_;
 protected:
   Fl_Shortcut shortcut_value;
   void do_end_hot_callback();
@@ -32,6 +33,9 @@ public:
   Fl_Shortcut_Button(int X,int Y,int W,int H, const char* l = 0);
   void value(Fl_Shortcut shortcut);
   Fl_Shortcut value();
+  void default_value(Fl_Shortcut shortcut);
+  Fl_Shortcut default_value();
+  void default_clear();
 };
 
 #endif // Fl_Shortcut_Button_H

fluid/Fl_Menu_Type.cxx

@@ -708,6 +708,7 @@ void shortcut_in_cb(Fl_Shortcut_Button* i, void* v) {
       i->parent()->hide();
       return;
     }
+    i->default_value( i->value() ); // enable the "undo" capability of the shortcut button
     i->show();
     i->parent()->show();
     i->redraw();

src/Fl_Shortcut_Button.cxx

@@ -46,8 +46,11 @@ Fl_Shortcut_Button::Fl_Shortcut_Button(int X,int Y,int W,int H, const char* l)
 : Fl_Button(X,Y,W,H,l),
   hot_(false),
   pre_hot_(false),
+  default_set_(false),
+  handle_default_button_(false),
   pre_esc_(0),
-  shortcut_value(0)
+  shortcut_value(0),
+  default_shortcut_(0)
 {
   box(FL_DOWN_BOX);
   selection_color(FL_SELECTION_COLOR);
@@ -72,6 +75,34 @@ Fl_Shortcut Fl_Shortcut_Button::value() {
   return shortcut_value;
 }
 
+/**
+ Set the default shortcut.
+ If set, and additional 'reverse' button apears that the user can click to
+ reset the shortcut to some default value (including 0).
+ \param[in] shortcut encoded as key and modifier
+ */
+void Fl_Shortcut_Button::default_value(Fl_Shortcut shortcut) {
+  default_shortcut_ = shortcut;
+  default_set_ = true;
+  redraw();
+}
+
+/**
+ Return the default shortcut.
+ \return shortcut encoded as key and modifier
+ */
+Fl_Shortcut Fl_Shortcut_Button::default_value() {
+  return default_shortcut_;
+}
+
+/**
+ No longer show the button to reverse to a default shortcut.
+ */
+void Fl_Shortcut_Button::default_clear() {
+  default_set_ = false;
+  redraw();
+}
+
 /**
  Draw the textual representation of the shortcut button.
 
@@ -103,7 +134,12 @@ void Fl_Shortcut_Button::draw() {
   const char *text = label();
   if (shortcut_value)
     text = fl_shortcut_label(shortcut_value);
-  fl_draw(text, X, Y, W, H, align() | FL_ALIGN_INSIDE);
+  if (default_set_) {
+    fl_draw(text, X, Y, W-H, H, align() | FL_ALIGN_INSIDE);
+    fl_draw_symbol("@-29undo", X+W-H, Y, H, H, textcol);
+  } else {
+    fl_draw(text, X, Y, W, H, align() | FL_ALIGN_INSIDE);
+  }
   if (Fl::focus() == this) draw_focus();
 }
 
@@ -120,6 +156,35 @@ void Fl_Shortcut_Button::do_end_hot_callback() {
  Handle keystrokes to catch the user's shortcut.
  */
 int Fl_Shortcut_Button::handle(int e) {
+  bool inside_default_button = false;
+  if (default_set_ && ( (e == FL_PUSH) || (e == FL_DRAG) || (e == FL_RELEASE) ) ) {
+    int X = x() + Fl::box_dx(box());
+    int Y = y() + Fl::box_dy(box());
+    int W = w() - Fl::box_dw(box());
+    int H = h() - Fl::box_dh(box());
+    if (Fl::event_inside(this) && (Fl::event_x() > X+W-H))
+      inside_default_button = true;
+  }
+  if ((e == FL_PUSH) && default_set_ && inside_default_button) {
+    if (Fl::visible_focus() && handle(FL_FOCUS)) Fl::focus(this);
+    handle_default_button_ = true;
+    return 1;
+  }
+  if (handle_default_button_) {
+    if (e == FL_DRAG)
+      return 1;
+    if (e == FL_RELEASE) {
+      if (inside_default_button && (shortcut_value != default_shortcut_)) {
+        shortcut_value = default_shortcut_;
+        set_changed();
+        redraw();
+        if (when() & FL_WHEN_CHANGED) do_callback(FL_REASON_CHANGED);
+        clear_changed();
+      }
+      handle_default_button_ = false;
+      return 1;
+    }
+  }
   switch (e) {
     case FL_PUSH:
       if (Fl::visible_focus() && handle(FL_FOCUS)) Fl::focus(this);
@@ -135,17 +200,19 @@ int Fl_Shortcut_Button::handle(int e) {
       if ((e == FL_RELEASE) && pre_hot_ && !hot_)
         do_end_hot_callback();
       redraw();
+      handle_default_button_ = false;
       return 1;
     case FL_UNFOCUS:
       if (hot_) do_end_hot_callback();
       hot_ = false;
+      handle_default_button_ = false;
       /* FALLTHROUGH */
     case FL_FOCUS:
       redraw();
       return 1;
     case FL_KEYBOARD:
       if (hot_) {
-        // Note: we can't really hanlde non-Latin shortcuts in the Fl_Shortcut
+        // Note: we can't really handle non-Latin shortcuts in the Fl_Shortcut
         //       type, so we don't handle them here either
         int v = fl_utf8decode(Fl::event_text(), 0, 0);
         if ( (v > 32 && v < 0x7f) || (v > 0xa0 && v <= 0xff) ) {