// Lock horizontal starting position + capture group bounding box into one "item" (so you can use IsItemHovered() or layout primitives such as SameLine() on whole group, etc.)
// Groups are currently a mishmash of functionalities which should perhaps be clarified and separated.
// If the current ActiveId was declared within the boundary of our group, we copy it to LastItemId so IsItemActive(), IsItemDeactivated() etc. will be functional on the entire group.
// It would be be neater if we replaced window.DC.LastItemId by e.g. 'bool LastItemIsActive', but would put a little more burden on individual widgets.
// Also if you grep for LastItemId you'll notice it is only used in that context.
// (The tests not symmetrical because ActiveIdIsAlive is an ID itself, in order to be able to handle ActiveId being overwritten during the frame.)
// (The two tests not the same because ActiveIdIsAlive is an ID itself, in order to be able to handle ActiveId being overwritten during the frame.)