I have a content that is 200x100. I give the container (i.e. Grid Panel or any other) Size To Content = True. That works fine.
Now if I also give the container offsets (i.e. 10,10,10,10), I expect the container to add the offsets and become 220x120. But instead it subtracts the offset from the content. The container will still be 200x100 but the content will now be cut off and become 180x80.
Observe the Grid Panel is shrinking down and cutting off the content, even though it has Size To Content checked.
The Canvas Panel still has the same size, instead of growing by 20x20.
After following the steps above it appears that this is working as intended. You have set the panel to size itself to its content, however you are then overriding the size of the grid panel but changing it’s anchors and applying an offset.
I see, so offset is intended to layout a top->bottom (outer->inner) layout. Since I want to use a bottom->up (inner->outer) layout, I can use the Size Box with Padding. That delivers the result I want.
(Still, I can see no situation where SizeToContent + offset makes sense. Since the outer container does still SizeToContent (It’s not a complete override), but then cuts it off by the offset.)