Animation: make TrackView constructors implicit.

For consistency with all other views such as Containers::ArrayView as
these are all relatively light types and so the construction should be
lightweight as well. OTOH, Track constructors are still explicit because
they're heavy and the user should experience the heaviness firsthand.

src/Magnum/Animation/Track.h

@@ -523,7 +523,7 @@ template<class K, class V, class R
          * return @cpp nullptr @ce, @ref at() always returns a
          * default-constructed value.
          */
-        explicit TrackView() noexcept {}
+        /*implicit*/ TrackView() noexcept {}
 
         /**
          * @brief Construct with custom interpolator
@@ -540,13 +540,13 @@ template<class K, class V, class R
          * @ref TrackView(const Containers::StridedArrayView<const K>&, const Containers::StridedArrayView<const V>&, Interpolation, Extrapolation, Extrapolation)
          * for an alternative.
          */
-        explicit TrackView(const Containers::StridedArrayView<const K>& keys, const Containers::StridedArrayView<const V>& values, Interpolator interpolator, Extrapolation before, Extrapolation after) noexcept: TrackViewStorage<K>{keys, values, Interpolation::Custom, interpolator, before, after} {}
+        /*implicit*/ TrackView(const Containers::StridedArrayView<const K>& keys, const Containers::StridedArrayView<const V>& values, Interpolator interpolator, Extrapolation before, Extrapolation after) noexcept: TrackViewStorage<K>{keys, values, Interpolation::Custom, interpolator, before, after} {}
 
         /** @overload
          * Equivalent to calling @ref TrackView(const Containers::StridedArrayView<const K>&, const Containers::StridedArrayView<const V>&, Interpolator, Extrapolation, Extrapolation)
          * with both @p before and @p after set to @p extrapolation.
          */
-        explicit TrackView(const Containers::StridedArrayView<const K>& keys, const Containers::StridedArrayView<const V>& values, Interpolator interpolator, Extrapolation extrapolation = Extrapolation::Extrapolated) noexcept: TrackView<K, V, R>{keys, values, interpolator, extrapolation, extrapolation} {}
+        /*implicit*/ TrackView(const Containers::StridedArrayView<const K>& keys, const Containers::StridedArrayView<const V>& values, Interpolator interpolator, Extrapolation extrapolation = Extrapolation::Extrapolated) noexcept: TrackView<K, V, R>{keys, values, interpolator, extrapolation, extrapolation} {}
 
         /**
          * @brief Construct with custom interpolator from an interleaved array
@@ -558,7 +558,7 @@ template<class K, class V, class R
          * Converts @p data to a pair of strided array views and calls
          * @ref TrackView(const Containers::StridedArrayView<const K>&, const Containers::StridedArrayView<const V>&, Interpolator, Extrapolation, Extrapolation).
          */
-        explicit TrackView(Containers::ArrayView<const std::pair<K, V>> data, Interpolator interpolator, Extrapolation before, Extrapolation after) noexcept: TrackView<K, V, R>{Containers::StridedArrayView<const K>{data ? &data[0].first : nullptr, data.size(), sizeof(std::pair<K, V>)}, Containers::StridedArrayView<const V>{data ? &data[0].second : nullptr, data.size(), sizeof(std::pair<K, V>)}, interpolator, before, after} {}
+        /*implicit*/ TrackView(Containers::ArrayView<const std::pair<K, V>> data, Interpolator interpolator, Extrapolation before, Extrapolation after) noexcept: TrackView<K, V, R>{Containers::StridedArrayView<const K>{data ? &data[0].first : nullptr, data.size(), sizeof(std::pair<K, V>)}, Containers::StridedArrayView<const V>{data ? &data[0].second : nullptr, data.size(), sizeof(std::pair<K, V>)}, interpolator, before, after} {}
 
         /** @overload
          * Equivalent to calling @ref TrackView(Containers::ArrayView<const std::pair<K, V>>, Interpolator, Extrapolation, Extrapolation)
@@ -581,13 +581,13 @@ template<class K, class V, class R
          * supply their own interpolator function to @ref at() or
          * @ref atStrict().
          */
-        explicit TrackView(const Containers::StridedArrayView<const K>& keys, const Containers::StridedArrayView<const V>& values, Interpolation interpolation, Interpolator interpolator, Extrapolation before, Extrapolation after) noexcept: TrackViewStorage<K>{keys, values, interpolation, interpolator, before, after} {}
+        /*implicit*/ TrackView(const Containers::StridedArrayView<const K>& keys, const Containers::StridedArrayView<const V>& values, Interpolation interpolation, Interpolator interpolator, Extrapolation before, Extrapolation after) noexcept: TrackViewStorage<K>{keys, values, interpolation, interpolator, before, after} {}
 
         /** @overload
          * Equivalent to calling @ref TrackView(const Containers::StridedArrayView<const K>&, const Containers::StridedArrayView<const V>&, Interpolation, Interpolator, Extrapolation, Extrapolation)
          * with both @p before and @p after set to @p extrapolation.
          */
-        explicit TrackView(const Containers::StridedArrayView<const K>& keys, const Containers::StridedArrayView<const V>& values, Interpolation interpolation, Interpolator interpolator, Extrapolation extrapolation = Extrapolation::Extrapolated) noexcept: TrackView<K, V, R>{keys, values, interpolation, interpolator, extrapolation, extrapolation} {}
+        /*implicit*/ TrackView(const Containers::StridedArrayView<const K>& keys, const Containers::StridedArrayView<const V>& values, Interpolation interpolation, Interpolator interpolator, Extrapolation extrapolation = Extrapolation::Extrapolated) noexcept: TrackView<K, V, R>{keys, values, interpolation, interpolator, extrapolation, extrapolation} {}
 
         /**
          * @brief Construct with both generic and custom interpolator from an interleaved array
@@ -600,13 +600,13 @@ template<class K, class V, class R
          * Converts @p data to a pair of strided array views and calls
          * @ref TrackView(const Containers::StridedArrayView<const K>&, const Containers::StridedArrayView<const V>&, Interpolator, Extrapolation, Extrapolation).
          */
-        explicit TrackView(Containers::ArrayView<const std::pair<K, V>> data, Interpolation interpolation, Interpolator interpolator, Extrapolation before, Extrapolation after) noexcept: TrackViewStorage<K>{Containers::StridedArrayView<const K>{data ? &data[0].first : nullptr, data.size(), sizeof(std::pair<K, V>)}, Containers::StridedArrayView<const V>{data ? &data[0].second : nullptr, data.size(), sizeof(std::pair<K, V>)}, interpolation, interpolator, before, after} {}
+        /*implicit*/ TrackView(Containers::ArrayView<const std::pair<K, V>> data, Interpolation interpolation, Interpolator interpolator, Extrapolation before, Extrapolation after) noexcept: TrackViewStorage<K>{Containers::StridedArrayView<const K>{data ? &data[0].first : nullptr, data.size(), sizeof(std::pair<K, V>)}, Containers::StridedArrayView<const V>{data ? &data[0].second : nullptr, data.size(), sizeof(std::pair<K, V>)}, interpolation, interpolator, before, after} {}
 
         /** @overload
          * Equivalent to calling @ref TrackView(Containers::ArrayView<const std::pair<K, V>>, Interpolation, Interpolator, Extrapolation, Extrapolation)
          * with both @p before and @p after set to @p extrapolation.
          */
-        explicit TrackView(Containers::ArrayView<const std::pair<K, V>> data, Interpolation interpolation, Interpolator interpolator, Extrapolation extrapolation = Extrapolation::Extrapolated) noexcept: TrackView<K, V, R>{data, interpolation, interpolator, extrapolation, extrapolation} {}
+        /*implicit*/ TrackView(Containers::ArrayView<const std::pair<K, V>> data, Interpolation interpolation, Interpolator interpolator, Extrapolation extrapolation = Extrapolation::Extrapolated) noexcept: TrackView<K, V, R>{data, interpolation, interpolator, extrapolation, extrapolation} {}
 
         /**
          * @brief Construct with generic interpolation behavior
@@ -622,13 +622,13 @@ template<class K, class V, class R
          * @p interpolation using @ref interpolatorFor(). See its documentation
          * for more information.
          */
-        explicit TrackView(const Containers::StridedArrayView<const K>& keys, const Containers::StridedArrayView<const V>& values, Interpolation interpolation, Extrapolation before, Extrapolation after) noexcept: TrackViewStorage<K>{keys, values, interpolation, interpolatorFor<V, R>(interpolation), before, after} {}
+        /*implicit*/ TrackView(const Containers::StridedArrayView<const K>& keys, const Containers::StridedArrayView<const V>& values, Interpolation interpolation, Extrapolation before, Extrapolation after) noexcept: TrackViewStorage<K>{keys, values, interpolation, interpolatorFor<V, R>(interpolation), before, after} {}
 
         /** @overload
          * Equivalent to calling @ref TrackView(const Containers::StridedArrayView<const K>&, const Containers::StridedArrayView<const V>&, Interpolation, Extrapolation, Extrapolation)
          * with both @p before and @p after set to @p extrapolation.
          */
-        explicit TrackView(const Containers::StridedArrayView<const K>& keys, const Containers::StridedArrayView<const V>& values, Interpolation interpolation, Extrapolation extrapolation = Extrapolation::Extrapolated) noexcept: TrackView<K, V, R>{keys, values, interpolation, extrapolation, extrapolation} {}
+        /*implicit*/ TrackView(const Containers::StridedArrayView<const K>& keys, const Containers::StridedArrayView<const V>& values, Interpolation interpolation, Extrapolation extrapolation = Extrapolation::Extrapolated) noexcept: TrackView<K, V, R>{keys, values, interpolation, extrapolation, extrapolation} {}
 
         /**
          * @brief Construct with generic interpolation behavior from an interleaved array
@@ -640,13 +640,13 @@ template<class K, class V, class R
          * Converts @p data to a pair of strided array views and calls
          * @ref TrackView(const Containers::StridedArrayView<const K>&, const Containers::StridedArrayView<const V>&, Interpolator, Extrapolation, Extrapolation).
          */
-        explicit TrackView(Containers::ArrayView<const std::pair<K, V>> data, Interpolation interpolation, Extrapolation before, Extrapolation after) noexcept: TrackView<K, V, R>{Containers::StridedArrayView<const K>{data ? &data[0].first : nullptr, data.size(), sizeof(std::pair<K, V>)}, Containers::StridedArrayView<const V>{data ? &data[0].second : nullptr, data.size(), sizeof(std::pair<K, V>)}, interpolation, before, after} {}
+        /*implicit*/ TrackView(Containers::ArrayView<const std::pair<K, V>> data, Interpolation interpolation, Extrapolation before, Extrapolation after) noexcept: TrackView<K, V, R>{Containers::StridedArrayView<const K>{data ? &data[0].first : nullptr, data.size(), sizeof(std::pair<K, V>)}, Containers::StridedArrayView<const V>{data ? &data[0].second : nullptr, data.size(), sizeof(std::pair<K, V>)}, interpolation, before, after} {}
 
         /** @overload
          * Equivalent to calling @ref TrackView(Containers::ArrayView<const std::pair<K, V>>, Interpolation, Extrapolation, Extrapolation)
          * with both @p before and @p after set to @p extrapolation.
          */
-        explicit TrackView(Containers::ArrayView<const std::pair<K, V>> data, Interpolation interpolation, Extrapolation extrapolation = Extrapolation::Extrapolated) noexcept: TrackView<K, V, R>{data, interpolation, extrapolation, extrapolation} {}
+        /*implicit*/ TrackView(Containers::ArrayView<const std::pair<K, V>> data, Interpolation interpolation, Extrapolation extrapolation = Extrapolation::Extrapolated) noexcept: TrackView<K, V, R>{data, interpolation, extrapolation, extrapolation} {}
 
         /**
          * @brief Interpolation function