// the panning speed threshold, no matter how far is the pan displacement, pan fast to left/right quickly (speed > 0.3) will turn over/back the page
const float GESTURE_SPEED_THRESHOLD(0.3f);
// the animation duration of turning the previous page back when an outwards flick is detected
const float PAGE_TURN_OVER_ANIMATION_DURATION(0.5f);
// the panning speed threshold, no matter how far is the pan displacement, pan fast to left/right quickly (speed > 0.3) will turn over/back the page
const float GESTURE_SPEED_THRESHOLD(0.3f);
// the animation duration of turning the previous page back when an outwards flick is detected
const float PAGE_TURN_OVER_ANIMATION_DURATION(0.5f);