Thanks guys for your tests.
I tried the downgrade, it makes first a compound that needs to be downgraded in turn, but after that, it is not possible to undowngrade (upgrade) ... I think.
I used CTRLZ to rollback, from the fusion, all was ok until the compound, but I didn't find the original roof again. it appears in the treeview, but is not visible (seems to have been reduced to a zero size).
Of course, the idea is to continue working with roofs... to be able to adjust its properties.
it will be nice if you find something in the code, rockn.
BTW, I have tried to make a roof with only one pane, I never succeed really (there is still one line beeing visible on one side)
- roof vanished after undo downgrade.PNG (16.05 KiB) Viewed 1643 times