When a bar chart does not have enough space (or when it thinks it is the case), it will rotate the tick labels by 90 degrees. There a two issues here :
1) It would be nice to be able to customize this, such as by rotation the label by 45° (making more easily readable). The problem being that the rotation is not even the same as the YAxis legend so it makes the chart a bit confusing.
I have found a workaround to prevent any rotation : manually set the tickLabelRotation at 360° (0 does not work). I feel really akward having to do that to prevent this label from turning...
2) Once the tickLabel have been turned by the application, they will not go back to being horizontal even though the scene become larger and would have enough space to do so.