message: Bug fix and some refactoring in ListBox.
diff: @@ -143,14 +143,13 @@ void ListBox::removeItem(const std::string& item)
  {
  mItems.erase(it);
  mCurrentSelection = constants::NO_SELECTION;
  + sort();
  + _updateItemDisplay();
  return;
  }
  ++it;
  }
  -
  - sort();
  - _updateItemDisplay();
  }
  @@ -239,16 +238,11 @@ void ListBox::onMouseMove(int x, int y, int relX, int relY)
  /**
  * \todo Make the scroll amount configurable.
  */
  -void ListBox::onMouseWheel(int x, int y) //-V751
  -{
  - if (y < 0)
  +void ListBox::onMouseWheel(int x, int y)
  {
  - mSlider.changeThumbPosition(16.0);
  - }
  - else if (y > 0)
  - {
  - mSlider.changeThumbPosition(-16.0);
  - }
  + if (empty() || !visible()) { return; }
  +
  + mSlider.changeThumbPosition((y < 0 ? 16.0 : -16.0));
  }
  