Description Laurent Redor 2017-06-19 04:20:20 EDT

+++ This bug was initially created as a clone of Bug #485010 +++

Steps to reproduce: 
> In a runtime, on master, open the docbook sample VSP
> open the sample aird model
> open the obvious diagram and create a chapter, a big section, a medium section, a tiny section and a note
> open the evoluate view diagram
> select "Sect2" and try to move it

You will get the following stack
> org.eclipse.core.commands.ExecutionException: While executing ... exception occurred
> at org.eclipse.core.commands.operations.DefaultOperationHistory.execute(:524)
> at org.eclipse.sirius.diagram.ui.tools.internal.editor.DDiagramCommandStack.exe..(71
> ...
> Caused by: java.lang.ArithmeticException: / by zero
>	at java.math.BigDecimal.divideAndRound(BigDecimal.java:4106)
>	at java.math.BigDecimal.divide(BigDecimal.java:5153)
>	at java.math.BigDecimal.divide(BigDecimal.java:1561)
>       at org.eclipse.draw2d.geometry.PrecisionGeometry.preciseDivide(l48)
>	at org.eclipse.draw2d.geometry.Vector.getAngle(Vector.java:168)
>	at oesd.ui.internal.edit.parts.locator.EdgeLabelQuery.getSameLineStatus(l507)

For the current case, both vectors are horizontal (and the edge is hidden, we see only the arrow), it seems we might use referenceVector.isParallelTo(vector) and then check the horizontallity/verticallity and direction before computing the angle.