In SequenceDiagram, observation points do or do not allow Message Creation depending on mouse movement

[peransin-obeo]

When having a observation point on a ExecutionMapping, the user may be forbidden to create a message depending on how the mouse moves over EditParts.

Symptoms:

• When entering the ExecutionMapping by the Observation Point part, it is possible to start creating a message but not possible to finish the action.
• When entering the ExecutionMapping by its body then moving to the observation point it is possible to start creating a message and to finish the action.

How to reproduce:

See attached video for mouse event sequence.

With provided interaction.odesign, use it org.eclipse.sirius.sample.interactions.design plugin from code.

• Creates 2 Lifelines and 1 Execution objects.
• Select 'read' tool
• Move to ObservationPoint without moving over neither the lifeline nor the Execution.
• Click and move to the next lifeline
• => Mouse cursor indicates no creation is possible.

Modifications of ODesign are:

• Greater size for ObservationPoint,
• Additional mapping for 'read' tool including ObservationPoint,
• Additional layer active by default.

Analysis

ObservationPointEditPart does not contain SequenceSiriusGraphicalNodeEditPolicy Edit Policy unlike ExecutionEditPart (or equivalent).

When selecting the source when creating a message, for nodes, the edit policy sets DRAW2D_EDGE_LOCATION_SOURCE data in CreateRequest.
This data is expected when selecting the target by getConnectionCompleteCommand to create the GEF Command.