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21 
22 
23 
24 #ifndef INCLUDED_SLIDESHOW_BOOLANIMATION_HXX
25 #define INCLUDED_SLIDESHOW_BOOLANIMATION_HXX
26 
27 #include "animation.hxx"
28 
29 
30 /* Definition of BoolAnimation interface */
31 
32 namespace slideshow
33 {
34     namespace internal
35     {
36         /** Interface defining a bool animation.
37 
38         	This interface is a specialization of the Animation
39         	interface, and is used to animate attributes that have
40         	only two discrete values (on and off, or true and false,
41         	for example).
42          */
43         class BoolAnimation : public Animation
44         {
45         public:
46             typedef bool ValueType;
47 
48             /** Set the animation to the given value
49 
50                 @param bValue
51                 Current animation value.
52              */
53             virtual bool operator()( ValueType bValue ) = 0;
54 
55             /** Request the underlying value for this animation.
56 
57             	This is necessary for pure To or By animations, as the
58             	Activity cannot determine a sensible start value
59             	otherwise.
60 
61                 @attention Note that you are only permitted to query
62                 for the underlying value, if the animation has actually
63                 been started (via start() call).
64              */
65             virtual ValueType getUnderlyingValue() const = 0;
66         };
67 
68         typedef ::boost::shared_ptr< BoolAnimation > BoolAnimationSharedPtr;
69 
70     }
71 }
72 
73 #endif /* INCLUDED_SLIDESHOW_BOOLANIMATION_HXX */
74