code: function (evt) {
              var target = evt.target;
              var val = parseInt(target.value, 10);
              var id = target.id;
  
              // Positive value was entered (negative values are allowed, but the boundaries would be off screen)
              if (val > 0) {
                  if ($showBoundsCheck.is(':checked')) {
                      $('.boundary-' + id).show();
                      _drawBound(id, val);
                  }
                  else {
                      $('.boundary-' + id).hide();
                  }
              }
              // Hide boundaries
              else {
                  $('.boundary-' + id).hide();
              }
  
              // Update the page
              withinviewport.defaults[id] = val;
              _updateBoxes();
              _toggleBoundaryToggle();
          }
docs: When a boundary value changes