AOO410/main/slideshow/source/engine/activities/interpolation.hxx

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#ifndef INCLUDED_SLIDESHOW_INTERPOLATION_HXX
#define INCLUDED_SLIDESHOW_INTERPOLATION_HXX

#include <basegfx/tools/lerp.hxx>

namespace basegfx
{
    namespace tools
    {
        // Interpolator specializations
        // ============================

        // NOTE: generic lerp is included from lerp.hxx. Following
        // are some specializations for various
        // not-straight-forward-interpolatable types

        /// Specialization for RGBColor, to employ color-specific interpolator
		template<> ::slideshow::internal::RGBColor lerp< ::slideshow::internal::RGBColor >( 
            const ::slideshow::internal::RGBColor& rFrom, 
            const ::slideshow::internal::RGBColor& rTo, 
            double			                       t	 )
        {
            return interpolate( rFrom, rTo, t );
        }
        
        /// Specialization also for sal_Int16, although this code should not be called
        template<> sal_Int16 lerp< sal_Int16 >( const sal_Int16&, 
                                                const sal_Int16& 	rTo, 
                                                double					   )
        {
            OSL_ENSURE( false,
                        "lerp<sal_Int16> called" );
            return rTo;
        }
        
		/// Specialization also for string, although this code should not be called
        template<> ::rtl::OUString lerp< ::rtl::OUString >( const ::rtl::OUString&, 
                                                            const ::rtl::OUString& 	rTo, 
                                                            double					     )
        {
            OSL_ENSURE( false,
                        "lerp<::rtl::OUString> called" );
            return rTo;
        }
        
		/// Specialization also for bool, although this code should not be called
        template<> bool lerp< bool >( const bool&, 
                                      const bool& 	rTo, 
                                      double		     )
        {
            OSL_ENSURE( false,
                        "lerp<bool> called" );
            return rTo;
        }
    }
}
        
namespace slideshow
{
    namespace internal
    {
        template< typename ValueType > struct Interpolator
        {
            ValueType operator()( const ValueType& 	rFrom, 
                                  const ValueType& 	rTo, 
                                  double			t ) const
            {
                return basegfx::tools::lerp( rFrom, rTo, t );
            }
        };
        
		/// Specialization for HSLColor, to employ color-specific interpolator
        template<> struct Interpolator< HSLColor >
        {
            Interpolator( bool bCCW ) :
                mbCCW( bCCW )
            {
            }

            HSLColor operator()( const HSLColor&	rFrom, 
                                 const HSLColor&	rTo, 
                                 double				t ) const
            {
                return interpolate( rFrom, rTo, t, mbCCW );
            }

        private:
            /// When true: interpolate counter-clockwise
            const bool mbCCW;
        };


		/** Generic linear interpolator

			@tpl ValueType
            Must have operator+ and operator* defined, and should
            have value semantics.

            @param rInterpolator
            Interpolator to use for lerp

            @param nFrame
            Must be in the [0,nTotalFrames) range

            @param nTotalFrames
            Total number of frames. Should be greater than zero.
        */
        template< typename ValueType > ValueType lerp( const Interpolator< ValueType >& rInterpolator,
                                                       const ValueType& 				rFrom, 
                                                       const ValueType& 				rTo, 
                                                       sal_uInt32						nFrame, 
                                                       ::std::size_t					nTotalFrames )
        {
            // TODO(P1): There's a nice HAKMEM trick for that
            // nTotalFrames > 1 condition below

            // for 1 and 0 frame animations, always take end value
            const double nFraction( nTotalFrames > 1 ? double(nFrame)/(nTotalFrames-1) : 1.0 );

            return rInterpolator( rFrom, rTo, nFraction );
        }

		/// Specialization for non-interpolatable constants/enums
        template<> sal_Int16 lerp< sal_Int16 >( const Interpolator< sal_Int16 >& 	/*rInterpolator*/,
                                                const sal_Int16& 					rFrom, 
                                                const sal_Int16& 					rTo, 
                                                sal_uInt32							nFrame, 
                                                ::std::size_t						nTotalFrames )
        {
            // until one half of the total frames are over, take from value.
            // after that, take to value. 
            // For nFrames not divisable by 2, we prefer to over from, which
            // also neatly yields to for 1 frame activities
            return nFrame < nTotalFrames/2 ? rFrom : rTo;
        }

		/// Specialization for non-interpolatable strings
        template<> ::rtl::OUString lerp< ::rtl::OUString >( const Interpolator< ::rtl::OUString >& 	/*rInterpolator*/,
                                                            const ::rtl::OUString& 					rFrom, 
                                                            const ::rtl::OUString& 					rTo, 
                                                            sal_uInt32								nFrame, 
                                                            ::std::size_t							nTotalFrames )
        {
            // until one half of the total frames are over, take from value.
            // after that, take to value. 
            // For nFrames not divisable by 2, we prefer to over from, which
            // also neatly yields to for 1 frame activities
            return nFrame < nTotalFrames/2 ? rFrom : rTo;
        }

		/// Specialization for non-interpolatable bools
        template<> bool lerp< bool >( const Interpolator< bool >& 	/*rInterpolator*/,
                                      const bool&					bFrom, 
                                      const bool&					bTo, 
                                      sal_uInt32					nFrame, 
                                      ::std::size_t					nTotalFrames )
        {
            // until one half of the total frames are over, take from value.
            // after that, take to value. 
            // For nFrames not divisable by 2, we prefer to over from, which
            // also neatly yields to for 1 frame activities
            return nFrame < nTotalFrames/2 ? bFrom : bTo;
        }
    }
}

#endif /* INCLUDED_SLIDESHOW_INTERPOLATION_HXX */