juce_AnimatedPosition.h

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 /*
  ==============================================================================
 
   This file is part of the JUCE library.
   Copyright (c) 2022 - Raw Material Software Limited
 
   JUCE is an open source library subject to commercial or open-source
   licensing.
 
   By using JUCE, you agree to the terms of both the JUCE 7 End-User License
   Agreement and JUCE Privacy Policy.
 
   End User License Agreement: www.juce.com/juce-7-licence
   Privacy Policy: www.juce.com/juce-privacy-policy
 
   Or: You may also use this code under the terms of the GPL v3 (see
   www.gnu.org/licenses).
 
   JUCE IS PROVIDED "AS IS" WITHOUT ANY WARRANTY, AND ALL WARRANTIES, WHETHER
   EXPRESSED OR IMPLIED, INCLUDING MERCHANTABILITY AND FITNESS FOR PURPOSE, ARE
   DISCLAIMED.
 
  ==============================================================================
*/
 
namespace juce
{
 
//==============================================================================
template <typename Behaviour>
class AnimatedPosition  : private Timer
{
public:
    AnimatedPosition()
        :  range (-std::numeric_limits<double>::max(),
                   std::numeric_limits<double>::max())
    {
    }
 
    void setLimits (Range<double> newRange) noexcept
    {
        range = newRange;
    }
 
    //==============================================================================
    void beginDrag()
    {
        grabbedPos = position;
        releaseVelocity = 0;
        stopTimer();
    }
 
    void drag (double deltaFromStartOfDrag)
    {
        moveTo (grabbedPos + deltaFromStartOfDrag);
    }
 
    void endDrag()
    {
        startTimerHz (60);
    }
 
    void nudge (double deltaFromCurrentPosition)
    {
        startTimerHz (10);
        moveTo (position + deltaFromCurrentPosition);
    }
 
    //==============================================================================
    double getPosition() const noexcept
    {
        return position;
    }
 
    void setPosition (double newPosition)
    {
        stopTimer();
        setPositionAndSendChange (newPosition);
    }
 
    //==============================================================================
    class Listener
    {
    public:
        virtual ~Listener() = default;
 
        virtual void positionChanged (AnimatedPosition&, double newPosition) = 0;
    };
 
    void addListener (Listener* listener)       { listeners.add (listener); }
 
    void removeListener (Listener* listener)    { listeners.remove (listener); }
 
    //==============================================================================
    Behaviour behaviour;
 
private:
    //==============================================================================
    double position = 0.0, grabbedPos = 0.0, releaseVelocity = 0.0;
    Range<double> range;
    Time lastUpdate, lastDrag;
    ListenerList<Listener> listeners;
 
    static double getSpeed (const Time last, double lastPos,
                            const Time now, double newPos)
    {
        auto elapsedSecs = jmax (0.005, (now - last).inSeconds());
        auto v = (newPos - lastPos) / elapsedSecs;
        return std::abs (v) > 0.2 ? v : 0.0;
    }
 
    void moveTo (double newPos)
    {
        auto now = Time::getCurrentTime();
        releaseVelocity = getSpeed (lastDrag, position, now, newPos);
        behaviour.releasedWithVelocity (newPos, releaseVelocity);
        lastDrag = now;
 
        setPositionAndSendChange (newPos);
    }
 
    void setPositionAndSendChange (double newPosition)
    {
        newPosition = range.clipValue (newPosition);
 
        if (! approximatelyEqual (position, newPosition))
        {
            position = newPosition;
            listeners.call ([this, newPosition] (Listener& l) { l.positionChanged (*this, newPosition); });
        }
    }
 
    void timerCallback() override
    {
        auto now = Time::getCurrentTime();
        auto elapsed = jlimit (0.001, 0.020, (now - lastUpdate).inSeconds());
        lastUpdate = now;
        auto newPos = behaviour.getNextPosition (position, elapsed);
 
        if (behaviour.isStopped (newPos))
            stopTimer();
        else
            startTimerHz (60);
 
        setPositionAndSendChange (newPos);
    }
 
    JUCE_DECLARE_NON_COPYABLE_WITH_LEAK_DETECTOR (AnimatedPosition)
};
 
} // namespace juce