Gap is not taken into account to compute sizes in toJSON()

[vincent-lecrubier-skydio]

Describe the bug

When gap=0, the api.fromJSON(api.toJSON()) operation is a no-op, as expected, we restore the layout exactly as it was saved.

But when gap>0, api.toJSON() operation actually changes the sizes (height, width) of elements a little bit (omitting gaps), which causes the api.fromJSON(api.toJSON()) to actually slightly change the layout. Doing this repeatedly (e.g. if the user edits and saves the layout multiple times) ends up changing the layout significantly

To Reproduce

Steps to reproduce the behavior:

1. have a dockview with gap=20
2. have a button to call api.fromJSON(api.toJSON())
3. click the button repeatedly
4. See error

Expected behavior

api.fromJSON(api.toJSON()) should be a no-op basically, not changing sizes

Screenshots

No issue when gap=0

https://www.loom.com/share/dec0b95292404ffbb858095918ee99df?sid=bdfe41d1-4f72-491e-93d3-9920ab826a60

Issue with gap>0

https://www.loom.com/share/e3bdd197762040eb904c61ea2eb4cb90?sid=bc202fe0-ad47-4ab7-a854-81562e0dc1a4