input_handler.h

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/*! \file
  \brief  The input handler interface

  \par Copyright Information

  Copyright (c) 2016 by The DiSTI Corporation.<br>
  11301 Corporate Blvd; Suite 100<br>
  Orlando, Florida 32817<br>
  USA<br>
  <br>
  All rights reserved.<br>

  This Software contains proprietary trade secrets of DiSTI and may not be
reproduced, in whole or part, in any form, or by any means of electronic,
mechanical, or otherwise, without the written permission of DiSTI.  Said
permission may be derived through the purchase of applicable DiSTI product
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Derivative Works based on this or other copyrighted DiSTI Software.

  NO WARRANTY. THE SOFTWARE IS PROVIDED "AS-IS," WITHOUT WARRANTY OF ANY KIND,
AND ANY USE OF THIS SOFTWARE PRODUCT IS AT YOUR OWN RISK. TO THE MAXIMUM EXTENT
PERMITTED BY APPLICABLE LAW, DISTI AND ITS SUPPLIERS DISCLAIM ALL WARRANTIES
AND CONDITIONS, EITHER EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE
IMPLIED WARRANTIES AND CONDITIONS OF MERCHANTABILITY AND/OR FITNESS FOR A
PARTICULAR PURPOSE, TITLE, AND NON-INFRINGEMENT, WITH REGARD TO THE SOFTWARE.

  LIMITATION OF LIABILITY. TO THE MAXIMUM EXTENT PERMITTED BY APPLICABLE LAW,
IN NO EVENT SHALL DISTI OR ITS SUPPLIERS BE LIABLE FOR ANY SPECIAL, INCIDENTAL,
INDIRECT, OR CONSEQUENTIAL DAMAGES WHATSOEVER (INCLUDING, WITHOUT LIMITATION,
DAMAGES FOR LOSS OF BUSINESS PROFITS, BUSINESS INTERRUPTION, LOSS OF BUSINESS
INFORMATION, OR ANY OTHER PECUNIARY LOSS) ARISING OUT OF THE USE OF OR
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  The aforementioned terms and restrictions are governed by the laws of the
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*/
#ifndef INCLUDED_INPUT_HANDLER_H
#define INCLUDED_INPUT_HANDLER_H

#include "disti_assert.h"
#include "gls_cpp_lang_support.h"
#include "weak_reference.h"

namespace disti
{
    class DisplayObject;
    class DisplayEvent;
    class KeyboardEvent;

    /** Class used to call a callback method that takes a KeyboardEvent */
    class KeyboardCallbackBase
    {
    public:
        /** call the callback with the provided display event */
        virtual void Call( KeyboardEvent* ev ) = 0;

        /** returns true if the callback is valid to call */
        virtual bool IsValid() const = 0;

        virtual ~KeyboardCallbackBase() {}
    };

    /** Interface for creating a callback from a class method.  The class must implement WeakReferenceable. 
      * Don't use this directly.  Use CreateInputHandlerCallback instead 
      */
    template <class T>
    class KeyboardMethodCallback : public KeyboardCallbackBase
    {
    public:
        typedef void ( T::*Callback )( KeyboardEvent* ev );

        KeyboardMethodCallback( Callback method, T* object )
            : _method( method )
            , _object( object )
        {
            DISTI_STATIC_ASSERT_IS_CONVERTIBLE_TO( T, WeakReferenceable );
            GLS_VERIFY( NULL != method );
            GLS_VERIFY( NULL != object );
        }

        void Call( KeyboardEvent* ev )
        {
            if( IsValid() )
            {
                ( _object.Get()->*( _method ) )( ev );
            }
        }

        virtual bool IsValid() const
        {
            return !_object.IsNull();
        }

    protected:
        Callback   _method;
        WeakRef<T> _object; 
    };

    /** helper method to create a KeyboardCallbackBase from a class method 
      * \param method a class method pointer
      * \param obj the object to call the method on
      */
    template <class Class>
    KeyboardCallbackBase* CreateInputHandlerCallback(
        const typename KeyboardMethodCallback<Class>::Callback method,
        Class* const                                           obj )
    {
        return new KeyboardMethodCallback<Class>( method, obj );
    }

    /** Base class implemented by all input handlers */
    class InputHandler
    {
    public:
        /// Type for unique identifiers
        typedef unsigned int ID;

        /** Handle the event
          * \param ev the event to handle
          * \return the object that handled the event, or NULL if no object handled the event
          */
        virtual DisplayObject* HandleInput( DisplayEvent* ev ) = 0;

        /** Register a global keyboard handler.  
          * \param callback the callback to call when a keyboard event occurs.  The input handler owns the callback and will delete it.
          * \return unique ID.  Used to unregister.
          */
        virtual ID RegisterGlobalKeyboardHandler( KeyboardCallbackBase* callback ) = 0;

        /** Unregister a global keyboard handler.  
          * \param id the unique identifier returned from RegisterGlobalKeyboardHandler.
          */
        virtual void UnregisterGlobalKeyboardHandler( ID id ) = 0;

        /** destructor */
        virtual ~InputHandler() {}
    };

} // namespace disti

#endif