private void startPanning(float x, float y, long time) {
float dx = mX.panDistance(x);
float dy = mY.panDistance(y);
double angle = Math.atan2(dy, dx); // range [-pi, pi]
angle = Math.abs(angle); // range [0, pi]
// When the touch move breaks through the pan threshold, reposition the touch down origin
// so the page won't jump when we start panning.
mX.startTouch(x);
mY.startTouch(y);
mLastEventTime = time;
if (!mX.scrollable() || !mY.scrollable()) {
setState(PanZoomState.PANNING);
} else if (angle < AXIS_LOCK_ANGLE || angle > (Math.PI - AXIS_LOCK_ANGLE)) {
mY.setScrollingDisabled(true);
setState(PanZoomState.PANNING_LOCKED);
} else if (Math.abs(angle - (Math.PI / 2)) < AXIS_LOCK_ANGLE) {
mX.setScrollingDisabled(true);
setState(PanZoomState.PANNING_LOCKED);
} else {
setState(PanZoomState.PANNING);
}
}
