tb_scroller.h

// ================================================================================
// ==      This file is a part of Turbo Badger. (C) 2011-2014, Emil Segerås      ==
// ==                     See tb_core.h for more information.                    ==
// ================================================================================

#ifndef TB_SCROLLER_H
#define TB_SCROLLER_H

#include "tb_core.h"
#include "tb_msg.h"

namespace tb {

class TBWidget;

class TBScrollerFunction
{
public:
    TBScrollerFunction(float decay) : m_decay(decay) {}

    float GetDurationFromSpeed(float start_speed);

    float GetSpeedFromDistance(float distance);

    float GetDistanceAtTime(float start_speed, float elapsed_time_ms);

    int GetDistanceAtTimeInt(float start_speed, float elapsed_time_ms);
private:
    float m_decay;
};

class TBScrollerSnapListener
{
public:
    virtual ~TBScrollerSnapListener() {};

    virtual void OnScrollSnap(TBWidget *target_widget, int &target_x, int &target_y) = 0;
};

class TBScroller : private TBMessageHandler
{
public:
    TBScroller(TBWidget *target);
    ~TBScroller();

    void SetSnapListener(TBScrollerSnapListener *listener) { m_snap_listener = listener; }

    void Start();

    void Stop();

    bool IsStarted() const { return m_is_started; }

    TBWidget *GetTarget() const { return m_target; }

    bool OnPan(int dx, int dy);

    void OnPanReleased();

    void OnScrollBy(int dx, int dy, bool accumulative);
private:
    virtual void OnMessageReceived(TBMessage *msg);
    bool IsScrolling();
    bool StopIfAlmostStill();
    void StopOrSnapScroll();
    void Reset();
    void AdjustToSnappingAndScroll(float ppms_x, float ppms_y);
    void Scroll(float start_speed_ppms_x, float start_speed_ppms_y);
    void GetTargetChildTranslation(int &x, int &y) const;
    void GetTargetScrollXY(int &x, int &y) const;
    TBWidget *m_target;
    TBScrollerSnapListener *m_snap_listener;
    TBScrollerFunction m_func;
    bool m_is_started;
    float m_pan_dx, m_pan_dy;
    float m_previous_pan_dx, m_previous_pan_dy;
    double m_pan_time_ms;
    double m_pan_delta_time_ms;
    float m_scroll_start_speed_ppms_x, m_scroll_start_speed_ppms_y;
    double m_scroll_start_ms;
    float m_scroll_duration_x_ms, m_scroll_duration_y_ms;
    int m_scroll_start_scroll_x, m_scroll_start_scroll_y;
    float m_pan_power_multiplier_x;
    float m_pan_power_multiplier_y;
    int m_expected_scroll_x;
    int m_expected_scroll_y;
};

} // namespace tb

#endif // TB_SCROLLER_H