RmlUi/Source/Core/ElementAnimation.h

#pragma once

#include "../../Include/RmlUi/Core/Header.h"
#include "../../Include/RmlUi/Core/Property.h"
#include "../../Include/RmlUi/Core/Tween.h"

namespace Rml {

struct AnimationKey {
	AnimationKey(float time, const Property& property, Tween tween) : time(time), property(property), tween(tween) {}
	float time;  // Local animation time (Zero means the time when the animation iteration starts)
	Property property;
	Tween tween; // Tweening between the previous and this key. Ignored for the first animation key.
};

// The origin is tracked for determining its behavior when adding and removing animations.
// User: Animation started by the Element API
// Animation: Animation started by the 'animation' property
// Transition: Animation started by the 'transition' property
enum class ElementAnimationOrigin : uint8_t { User, Animation, Transition };

class ElementAnimation {
private:
	PropertyId property_id = PropertyId::Invalid;

	float duration = 0;               // for a single iteration
	int num_iterations = 0;           // -1 for infinity
	bool alternate_direction = false; // between iterations

	Vector<AnimationKey> keys;

	double last_update_world_time = 0;
	float time_since_iteration_start = 0;
	int current_iteration = 0;
	bool reverse_direction = false;

	bool animation_complete = false;
	ElementAnimationOrigin origin = ElementAnimationOrigin::User;

	bool InternalAddKey(float time, const Property& property, Element& element, Tween tween);

	float GetInterpolationFactorAndKeys(int* out_key0, int* out_key1) const;

public:
	ElementAnimation() {}
	ElementAnimation(PropertyId property_id, ElementAnimationOrigin origin, const Property& current_value, Element& element, double start_world_time,
		float duration, int num_iterations, bool alternate_direction);

	bool AddKey(float target_time, const Property& property, Element& element, Tween tween, bool extend_duration);

	Property UpdateAndGetProperty(double time, Element& element);

	PropertyId GetPropertyId() const { return property_id; }
	float GetDuration() const { return duration; }
	bool IsComplete() const { return animation_complete; }
	bool IsTransition() const { return origin == ElementAnimationOrigin::Transition; }
	bool IsInitalized() const { return !keys.empty(); }
	float GetInterpolationFactor() const { return GetInterpolationFactorAndKeys(nullptr, nullptr); }
	ElementAnimationOrigin GetOrigin() const { return origin; }
};

} // namespace Rml