pub fn stack_zpos(entries: &mut [StackEntry<'_>]) -> boolExpand description
Number the armed planes’ zpos densely, in requested order.
A mutable plane gets max(previous + 1, zpos_min); a fixed-slot plane keeps
its slot. Only the planes actually armed take values, so layers that end up
composited do not use up the range, and the stack stays clear of its top,
which some controllers advertise but refuse (the SA8155P advertises
[0, 10] and rejects 9 and 10 even on a lone plane). Ties are broken by
plane id, except that a below_ties entry goes under the others. Order is
preserved, so stacking_consistent’s rulings stand.
Greedy-lowest is optimal, so when it overflows a plane’s zpos_max, or meets
a fixed slot at or below the previous value, no dense numbering exists:
every written is left equal to requested and this returns false.
Entries with no requested zpos or no zpos range are not numbered.