Is it possible in Roassal to draw nodes in a layout with different opacities? A simple example would be: drawing a tree with nodes less opaque the deeper their nesting level is.

Well... You will need to manually assign the color to the nodes. 

I've just made the following example:


Alpha is interesting to make translucent colors.

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view shape rectangle borderColor: Color veryVeryLightGray.
view nodes: (T copyFrom: 1 to: 10) forEach: [ :aClass | 
view shape rectangle borderColor: Color white.
view nodes: aClass methods.

view shape line color: (Color blue alpha: 0.2).
view edges: aClass methods from: #yourself toAll: [ :m | m queryAllOutgoingInvocations opposites asArray ].
view gridLayout.
].
view gridLayout.
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Alexandre Bergel  http://www.bergel.eu
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