kc/src/libcmpp/fltk/Fl_CbLinker.h

//| Copyright: (C) 2019-2020 Kevin Larke <contact AT larke DOT org> 
//| License: GNU GPL version 3.0 or above. See the accompanying LICENSE file.
#ifndef Fl_CbLinker_h
#define Fl_CbLinker_h

class Fl_Widget;
class Fl_Button;
class Fl_Scrollbar;
class Fl_Menu_Button;
struct Fl_Menu_Item;

/* 
This class solves the problem of linking static control callback functions
to an object instance. 

registerCtl() creates a record which links a control to an instance
of a Fl_CbLinker. The control is then given a static callback function:
_s_callback().  When _s_callback() is called from the control event
handler it links locates the controls link record an calls the
appropriate handler (e.g. onButton(), onScrollBar(), etc.)
*/

class Fl_CbLinker
{
 public:
  Fl_CbLinker();
  virtual ~Fl_CbLinker();

  void registerCtl( Fl_Button*      c, unsigned id );
  void registerCtl( Fl_Scrollbar*   c, unsigned id ); 
  void registerCtl( Fl_Menu_Button* c, unsigned id );
  void registerCtl( Fl_Menu_Item*   c, unsigned id );

  virtual void onButton(    Fl_Button*      c, unsigned id );
  virtual void onScrollbar( Fl_Scrollbar*   c, unsigned id );
  virtual void onMenuBtn(   Fl_Menu_Button* c, unsigned id );
  virtual void onMenuItem(  Fl_Menu_Item*   c, unsigned id );

 private:
  enum
  {
    kButtonTId,
    kScrollbarTId,
    kMenuBtnTId,
    kMenuItemTId
  };

  typedef struct ctl_str
  {
    Fl_CbLinker* thisPtr;
    unsigned     typeId;
    unsigned     ctlId;
    union
    {
      Fl_Button*      btn;
      Fl_Scrollbar*   sb;
      Fl_Menu_Button* mbtn;
      Fl_Menu_Item*   mitem;
      Fl_Widget*      w;
    } u;

  ctl_str( Fl_CbLinker* t, Fl_Button*      c, unsigned id)  : thisPtr(t), typeId(kButtonTId),   ctlId(id) { u.btn=c; }
  ctl_str( Fl_CbLinker* t, Fl_Scrollbar*   c, unsigned id ) : thisPtr(t), typeId(kScrollbarTId),ctlId(id) { u.sb=c; }
  ctl_str( Fl_CbLinker* t, Fl_Menu_Button* c, unsigned id ) : thisPtr(t), typeId(kMenuBtnTId),  ctlId(id) { u.mbtn=c; }
  ctl_str( Fl_CbLinker* t, Fl_Menu_Item*   c, unsigned id ) : thisPtr(t), typeId(kMenuItemTId), ctlId(id) { u.mitem=c; }

  } ctl_t;

  std::vector< ctl_t* > _ctlV;

  static void _s_callback( Fl_Widget* w, void* arg );
};

#endif