When the graphics info contains negative coordinates, the diagram generation in Activiti mess up. It always assumes the canvas space to be X(0, width) Y(0, height). Because of this, there are two issues:
1. The height and width of canvas is lesser than that of actual diagram.
2. The portion of the diagram, with negative coordinates get cut off.
Issue seems to be in initProcessDiagramCanvas() of DefaultProcessDiagramGenerator.java.