Just some commentary on the different cases - mainly thinking out loud to clarify my own thoughts...

You can see in all case el1 to el8, the child elements have shifted in relation to el0.
However the hotspot remains aligned with the location in el0.

I think part of the problem is that ROChildrenShape is a ROAbstractEndingShape and is always at the end of the line - so the translation is applied to the children elements.
Whereas it might work better if the position of the child elements was not affected by ROTranslatingShape, such that it becomes the reference for the position of any other translated shapes.
This would require ROChildrenShape be always the first shape of an element, rather than always be the last shape.
--------------------

The following code snippet...
el := ROElement on: 1.
(el + ROBorder + ROTranslatingShape + ROLabel ) inspect.
produces shapes chained in order of: ROLabel-->ROTranslatingShape-->ROBorder-->ROChildrenShape.
which seems reversed from what I would intuitively expect reading the code left to right.
I think ideally the shape chain would be: ROChildrenShape-->ROBorder-->ROTranslatingShape-->ROLabel-->RONullShape

Otherwise as in el1 you can see the position of the label is the same as el0, since the label has actually been drawn first prior to the translation, and instead the translation is applied to the border and child elements, the latter of which affects the mouse hotspot.

cheers, Ben

Ben Coman wrote:

I was trying to apply ROTranslatingShape to produce a label sitting above the children nodes. To understand it better how to get what I
need, I made ROExample>>nestingTranslate to show a permutation of the order the shapes can be applied. I have attached a screen snapshot and fileout for this. The case I am particularly interested in is el3.
The 'el0' case is the reference without any ROTranslatingShape.
When running the example hover near and over the inner elements to view the misalignment of the mouse hotspot. I have marked the approximate offset in green in the snapshot.

I notice that the existing call chain goes...
ROView>>localElementAt:
ROElement>>elementAt:
ROElement>>contains:
ROElemenet>>bounds
ROShape>>extentFor: (union of extent of each shape)

It seems to me the hotspot misalignment is related to the translation being applied at the shape draw level whereas the #contains: checking is done at the element level. This relies on the union of the shape extents to set the element bounds, but I can't see how that extent union could be modified to account for the translation - particular in the case of a negative translation since extents throw away information
about any negative offset.
So I thought perhaps that the element #contains: checking needs might be better chained through the shaped, so that the translation
could be applied similar to ROTranslatingShape>>chainedDrawOn:for: and that this would not cause any/much additional computation since all the shapes were being cycled through anyway for #extentFor:

Something like...
ROView>>localElementAt:
ROElement>>elementAt:
ROElement>>contains:
ROShape>>chainedContains:For: (for each shape)

cheers, Ben
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