movePage method
Implementation
bool movePage(Offset delta) {
final bool canMoveHorizontal = delta.dx != 0 &&
((delta.dx < 0 && boundary.right) ||
(delta.dx > 0 && boundary.left) ||
!_computeHorizontalBoundary);
final bool canMoveVertical = delta.dy != 0 &&
((delta.dy < 0 && boundary.bottom) ||
(delta.dy > 0 && boundary.top) ||
!_computeVerticalBoundary);
return canMoveHorizontal || canMoveVertical || totalScale! <= 1.0;
}