Creation tool uses the wrong location when creating a border node from inner container in a Stack

[mypsycho]

Use case:
It is possible in ContainerMapping to create an inner ContainerMapping using childrenPresentation as ContainerLayout.VERTICAL_STACK.
This designs creates a separation between the title zone and the Free form zone.
In this design, the click zone to create a border node is very limited.
A solution is to add the inner ContainerMapping in extraMappings of the NodeCreation tool.

The issue is, in this configuration, location to create the view of a new element is wrong :

[mypsycho]

Analysis:
The issue takes place in the following method:

sirius-desktop/plugins/org.eclipse.sirius.diagram.ui/src-diag/org/eclipse/sirius/diagram/ui/internal/refresh/AbstractCanonicalSynchronizer.java

Line 547 in 130c209

private LayoutDataResult updateAbstractDNode_ownedBorderedNodes_Bounds(View createdView) {

On classic mapping (ContainerMapping with FreeForm),
this method can find the proper layoutData as the layoutData target the container of the created portNode.

But when using a combinaison ContainerMapping{vertical_stack} + ContainerMapping{FreeForm}, layoutData is not found and port is placed on default location (left/top corner).

A solution may be to update the behavior of SiriusLayoutDataManager.INSTANCE.getData(portNode, true) invocation to also consider that layoutData targeting a child of the container is valid match.

See this method to search the proper location:

sirius-desktop/plugins/org.eclipse.sirius.diagram.ui/src-diag/org/eclipse/sirius/diagram/ui/business/internal/view/SiriusLayoutDataManagerImpl.java

Line 307 in 130c209

public LayoutData getData(final AbstractDNode node, final boolean searchParent) {

[lredor]

Step to reproduce:

• Import project Issue396 from Issue396ProjectSample.zip
• Open the diagram root class diagram
• Execute the tool EReference by clicking in the middle of the right border of Class1
• Expected: A border node is created on the click location.
• Observed: A border node is created in the top left corner of Class1.
  

[lredor]

Step to reproduce:

• Import project Issue396 from Issue396ProjectSample.zip
• ...

Issue396ProjectSample-v2.zip
This project sample is more complete:

• a standard container (free form),
• a list container,
• a container with several levels of regions.
  With a tool associated with each type of container, it allows you to compare the different cases.

[lredor]

@mypsycho Thank for your analysis, however I think it will be simpler to do the right processing upstream. That is to say, add the correct "LayoutData", with the correct parent edit part associated with the tool, when creating commands in org.eclipse.sirius.diagram.ui.graphical.edit.policies.NodeCreationEditPolicy.
Indeed, doing this in updateAbstractDNode_ownedBorderedNodes_Bounds would force us to redo the calculation of "relative/absolute" positions when we do not have all the necessary elements.