tag_win.h

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#ifndef TAGGED_WINDOW_SUPPORT
#define TAGGED_WINDOW_SUPPORT

/*****************************************************************************\
*                                                                             *
*  Name   : Chris Koeritz                                                     *
*  Author : tag & tagged_window                                               *
*                                                                             *
*  Purpose:                                                                   *
*                                                                             *
*    Provides a way to associate an object with a window.  One creates a tag  *
*    to represent the name of the object, then uses the tag to attach the     *
*    tagged_window class to the window.  Subsequently, the tagged_window can  *
*    be retrieved given the tag to search for.  Probably the most effective   *
*    way to use it is to derive your object from a tagged_window and then use *
*    the find() function and dynamic_cast<> to get back to your original      *
*    object.                                                                  *
*                                                                             *
*******************************************************************************
* Copyright (c) 1996-$now By Author.  This program is free software; you can  *
* redistribute it and/or modify it under the terms of the GNU General Public  *
* License as published by the Free Software Foundation; either version 2 of   *
* the License or (at your option) any later version.  This is online at:      *
*     http://www.fsf.org/copyleft/gpl.html                                    *
* Please send any updates to: fred@gruntose.com                               *
\*****************************************************************************/

#include "winexdll.h"

#include <basis/istring.h>
#include <basis/portable.h>

class WINDOWS_EXTENSIONS_CLASS_STYLE tag
{
public:
  tag(const istring &name = istring());
    // creates a tag using the "name" as the unique identifier for an atom
    // (the "name" should probably be the name of the class that wants to
    // create a tagged_window, providing the name is unique).
  tag(const tag &to_copy);
  ~tag();
    // releases the atom.

  istring name() const { return my_name; }

  tag &operator = (const tag &to_copy);

private:
  friend class tagged_window;
  istring my_name;  // the name of the atom(s).
#ifdef __WIN32__
  ATOM atom;  // atom used to hold pointer as a property.
#else
  ATOM atom_l;  // win16 needs two atoms for a 32 bit pointer.
  ATOM atom_h;
#endif

  void create(const istring &name);  // creates the atom(s) for "name".
  void whack();  // releases the atom(s).
};


class WINDOWS_EXTENSIONS_CLASS_STYLE tagged_window
{
public:
  tagged_window(const tag &name_tag);
    // creates an unattached tagged_window.

  ~tagged_window();
    // removes the tag from the window, if it was ever attached.

  void attach(window_handle window);
    // attaches this object to the "window" specified by using the unique name
    // passed to the constructor.  this tagged_window can later be retrieved
    // by looking up the tag with find().

  void detach();
    // removes the property from our window and forgets the window's handle.

  static const tagged_window *find(window_handle window, const tag &to_find);
    // returns the tagged_window associated with the "window" that had
    // a tag equivalent to "to_find" attached to it.  if the tagged_window
    // cannot be found, then NIL is returned.

  const tag &name() const { return name_tag; }
    // returns the name tag for this window.

private:
  window_handle window;  // the window of interest.
  tag name_tag;  // what to use as a tag for the window.
  bool attached;  // are we currently connected to the window?

  // prohibited: copy constructor and assignment.
  tagged_window(const tagged_window &to_copy);
  tagged_window &operator = (const tagged_window &to_copy);
};

#endif

---