SceneGraph: don't pass duration in Animable constructor.

It gets lost in the whole parameter list, using protected function
setDuration() instead. Default is `0.0f`, which means infinite duration.

src/SceneGraph/Animable.h

@@ -60,8 +60,8 @@ which takes care of running the animations.
 
 First thing is add Animable feature to some object and implement
 animationStep(). You can do it conveniently using multiple inheritance (see
-@ref scenegraph-features for introduction). You need to pass animation
+@ref scenegraph-features for introduction). Override animationStep() to
-duration to constructor, animationStep() provides both absolute animation
+implement your animation, the function provides both absolute animation
 time and time delta. Example:
 @code
 typedef SceneGraph::Object<SceneGraph::MatrixTransformation3D<>> Object3D;
@@ -69,7 +69,8 @@ typedef SceneGraph::Scene<SceneGraph::MatrixTransformation3D<>> Scene3D;
 
 class AnimableObject: public Object3D, SceneGraph::Animable3D<> {
     public:
-        AnimableObject(Object* parent = nullptr, SceneGraph::DrawableGroup3D<>* group = nullptr): Object3D(parent), SceneGraph::Animable3D<>(this, 10.0f, group) {
+        AnimableObject(Object* parent = nullptr, SceneGraph::DrawableGroup3D<>* group = nullptr): Object3D(parent), SceneGraph::Animable3D<>(this, group) {
+            setDuration(10.0f);
             // ...
         }
 
@@ -141,15 +142,13 @@ class MAGNUM_SCENEGRAPH_EXPORT Animable: public AbstractGroupedFeature<dimension
         /**
          * @brief Constructor
          * @param object    %Object this animable belongs to
-         * @param duration  Duration of the animation cycle in seconds. Set to
-         *      0 for infinite non-repeating animation.
          * @param group     Group this animable belongs to
          *
-         * Creates stopped non-repeating animation with specified duration,
+         * Creates stopped non-repeating animation with infinite duration,
          * adds the feature to the object and also to group, if specified.
-         * @see setRepeated(), AnimableGroup::add()
+         * @see setDuration(), setState(), setRepeated(), AnimableGroup::add()
          */
-        explicit Animable(AbstractObject<dimensions, T>* object, GLfloat duration, AnimableGroup<dimensions, T>* group = nullptr);
+        explicit Animable(AbstractObject<dimensions, T>* object, AnimableGroup<dimensions, T>* group = nullptr);
 
         /** @brief Animation duration */
         inline GLfloat duration() const { return _duration; }
@@ -213,6 +212,19 @@ class MAGNUM_SCENEGRAPH_EXPORT Animable: public AbstractGroupedFeature<dimension
         const AnimableGroup<dimensions, T>* group() const;
 
     protected:
+        /**
+         * @brief Set animation duration
+         * @return Pointer to self (for method chaining)
+         *
+         * Sets duration of the animation cycle in seconds. Set to `0.0f` for
+         * infinite non-repeating animation. Default is `0.0f`.
+         */
+        /* Protected so only animation implementer can change it */
+        inline Animable<dimensions, T>* setDuration(GLfloat duration) {
+            _duration = duration;
+            return this;
+        }
+
         /**
          * @brief Perform animation step
          * @param time      Time from start of the animation
@@ -294,7 +306,7 @@ class MAGNUM_SCENEGRAPH_EXPORT Animable: public AbstractGroupedFeature<dimension
         inline virtual void animationStopped() {}
 
     private:
-        const GLfloat _duration;
+        GLfloat _duration;
         GLfloat startTime, pauseTime;
         AnimationState previousState;
         AnimationState currentState;

src/SceneGraph/Animable.hpp

@@ -26,7 +26,7 @@
 
 namespace Magnum { namespace SceneGraph {
 
-template<std::uint8_t dimensions, class T> Animable<dimensions, T>::Animable(AbstractObject<dimensions, T>* object, GLfloat duration, AnimableGroup<dimensions, T>* group): AbstractGroupedFeature<dimensions, Animable<dimensions, T>, T>(object, group), _duration(duration), startTime(std::numeric_limits<GLfloat>::infinity()), pauseTime(-std::numeric_limits<GLfloat>::infinity()), previousState(AnimationState::Stopped), currentState(AnimationState::Stopped), _repeated(false), _repeatCount(0), repeats(0) {}
+template<std::uint8_t dimensions, class T> Animable<dimensions, T>::Animable(AbstractObject<dimensions, T>* object, AnimableGroup<dimensions, T>* group): AbstractGroupedFeature<dimensions, Animable<dimensions, T>, T>(object, group), _duration(0.0f), startTime(std::numeric_limits<GLfloat>::infinity()), pauseTime(-std::numeric_limits<GLfloat>::infinity()), previousState(AnimationState::Stopped), currentState(AnimationState::Stopped), _repeated(false), _repeatCount(0), repeats(0) {}
 
 template<std::uint8_t dimensions, class T> Animable<dimensions, T>* Animable<dimensions, T>::setState(AnimationState state) {
     if(currentState == state) return this;

src/SceneGraph/Test/AnimableTest.cpp

@@ -51,7 +51,9 @@ AnimableTest::AnimableTest() {
 void AnimableTest::state() {
     class StateTrackingAnimable: public SceneGraph::Animable<3> {
         public:
-            StateTrackingAnimable(AbstractObject<3>* object, AnimableGroup<3>* group = nullptr): SceneGraph::Animable<3>(object, 1.0f, group) {}
+            StateTrackingAnimable(AbstractObject<3>* object, AnimableGroup<3>* group = nullptr): SceneGraph::Animable<3>(object, group) {
+                setDuration(1.0f);
+            }
 
             std::string trackedState;
 
@@ -139,7 +141,8 @@ void AnimableTest::state() {
 
 class OneShotAnimable: public SceneGraph::Animable<3> {
     public:
-        OneShotAnimable(AbstractObject<3>* object, AnimableGroup<3>* group = nullptr): SceneGraph::Animable<3>(object, 10.0f, group), time(-1.0f) {
+        OneShotAnimable(AbstractObject<3>* object, AnimableGroup<3>* group = nullptr): SceneGraph::Animable<3>(object, group), time(-1.0f) {
+            setDuration(10.0f);
             setState(AnimationState::Running);
         }
 
@@ -163,7 +166,7 @@ class OneShotAnimable: public SceneGraph::Animable<3> {
 void AnimableTest::step() {
     class InifiniteAnimable: public SceneGraph::Animable<3> {
         public:
-            InifiniteAnimable(AbstractObject<3>* object, AnimableGroup<3>* group = nullptr): SceneGraph::Animable<3>(object, 0.0f, group), time(-1.0f), delta(0.0f) {}
+            InifiniteAnimable(AbstractObject<3>* object, AnimableGroup<3>* group = nullptr): SceneGraph::Animable<3>(object, group), time(-1.0f), delta(0.0f) {}
 
             GLfloat time, delta;
 
@@ -222,7 +225,8 @@ void AnimableTest::duration() {
 void AnimableTest::repeat() {
     class RepeatingAnimable: public SceneGraph::Animable<3> {
         public:
-            RepeatingAnimable(AbstractObject<3>* object, AnimableGroup<3>* group = nullptr): SceneGraph::Animable<3>(object, 10.0f, group), time(-1.0f) {
+            RepeatingAnimable(AbstractObject<3>* object, AnimableGroup<3>* group = nullptr): SceneGraph::Animable<3>(object, group), time(-1.0f) {
+                setDuration(10.0f);
                 setState(AnimationState::Running);
                 setRepeated(true);
             }