1. For the layer above a group
2. For the group above a layer, or a group
3. For the layer above a layer or a group that has layer mask
4. For the layer that has layer mask above a layer or a group (that has layer mask)
I was working in CSP and using clipping masks all over the layering quite often, just wish these features are available in Paintstorm too
Because painstorm's brush engine is unbeatable IMO, love it so much, and it has a Linux version.