Made all files show up.

OK, I finally did it, but I had to delete my local copy of this
repository, re-clone it, and then re-download the offending file into
my reset local copy of this repository!  (Sheesh!)

GUI.h

@@ -0,0 +1,133 @@
+
+//
+// This is a GUI support code to the chapters 12-16 of the book
+// "Programming -- Principles and Practice Using C++" by Bjarne Stroustrup
+//
+
+#ifndef GUI_GUARD
+#define GUI_GUARD
+
+#include "Window.h"
+#include "Graph.h"
+
+namespace Graph_lib {
+
+//------------------------------------------------------------------------------
+
+    typedef void* Address;    // Address is a synonym for void*
+    typedef void(*Callback)(Address, Address);    // FLTK's required function type for all callbacks
+
+//------------------------------------------------------------------------------
+
+    template<class W> W& reference_to(Address pw)
+    // treat an address as a reference to a W
+    {
+        return *static_cast<W*>(pw);
+    }
+
+//------------------------------------------------------------------------------
+
+    class Widget {
+    // Widget is a handle to an Fl_widget - it is *not* an Fl_widget
+    // We try to keep our interface classes at arm's length from FLTK
+    public:
+        Widget(Point xy, int w, int h, const string& s, Callback cb)
+            : loc(xy), width(w), height(h), label(s), do_it(cb)
+        {}
+
+        virtual void move(int dx,int dy) { hide(); pw->position(loc.x+=dx, loc.y+=dy); show(); }
+        virtual void hide() { pw->hide(); }
+        virtual void show() { pw->show(); }
+        virtual void attach(Window&) = 0;
+
+        Point loc;
+        int width;
+        int height;
+        string label;
+        Callback do_it;
+
+        virtual ~Widget() { }
+
+    protected:
+        Window* own;    // every Widget belongs to a Window
+        Fl_Widget* pw;  // connection to the FLTK Widget
+    private:
+        Widget& operator=(const Widget&); // don't copy Widgets
+        Widget(const Widget&);
+    };
+
+//------------------------------------------------------------------------------
+
+    struct Button : Widget {
+        Button(Point xy, int w, int h, const string& label, Callback cb)
+            : Widget(xy,w,h,label,cb)
+        {}
+
+        void attach(Window&);
+    };
+
+//------------------------------------------------------------------------------
+
+    struct In_box : Widget {
+        In_box(Point xy, int w, int h, const string& s)
+            :Widget(xy,w,h,s,0) { }
+        int get_int();
+        string get_string();
+
+        void attach(Window& win);
+    };
+
+//------------------------------------------------------------------------------
+
+    struct Out_box : Widget {
+        Out_box(Point xy, int w, int h, const string& s)
+            :Widget(xy,w,h,s,0) { }
+        void put(int);
+        void put(const string&);
+
+        void attach(Window& win);
+    };
+
+//------------------------------------------------------------------------------
+
+    struct Menu : Widget {
+        enum Kind { horizontal, vertical };
+        Menu(Point xy, int w, int h, Kind kk, const string& label)
+            : Widget(xy,w,h,label,0), k(kk), offset(0)
+        {}
+
+        Vector_ref<Button> selection;
+        Kind k;
+        int offset;
+        int attach(Button& b);      // Menu does not delete &b
+        int attach(Button* p);      // Menu deletes p
+
+        void show()                 // show all buttons
+        {
+            for (unsigned int i = 0; i<selection.size(); ++i)
+                selection[i].show();
+        }
+        void hide()                 // hide all buttons
+        {
+            for (unsigned int i = 0; i<selection.size(); ++i) 
+                selection[i].hide(); 
+        }
+        void move(int dx, int dy)   // move all buttons
+        {
+            for (unsigned int i = 0; i<selection.size(); ++i) 
+                selection[i].move(dx,dy);
+        }
+
+        void attach(Window& win)    // attach all buttons
+        {
+            for (int i=0; i<selection.size(); ++i) win.attach(selection[i]);
+            own = &win;
+        }
+
+    };
+
+//------------------------------------------------------------------------------
+
+} // of namespace Graph_lib
+
+#endif // GUI_GUARD