Doing some layout class

Hello again,
Merry Christmas also. 🎅

... Let's says... like if ... I needed to code my own Layout class... for some purpose.
I couldn't find any example to do that anywhere, but I guess most job is in GM_LAYOUT...
... and well I was asking myself 2 questions so far:

- Is gadget recursion managed in a layout done by intuition methods "AddGadget() / RemoveGadget() ", or by just using DoGadgetMethod() recursively for all GM_XX methods ?
Isn't calling DoGadgetMethod() recursively under a GM_RENDER dangerous ?

- Let's say: I add or remove a gadget under my own layout, how do I send refresh message to myself so it reaches GM_LAYOUT , like when resize is done ?

Thank youhappy new year also