prepare
Resolves native attachment requests after final layout, producing each attachment at most once.
Every request is validated before any producer or drawing output is invoked. Unavailable permits or a producer returning no capture keep the exact previous token and snapshot; an initial canvas remains transparent. The supplied command list and original runtime frame are never mutated.
Return
detached immutable presentation; its targets remain pinned until consumption or cancellation.
Parameters
complete immutable core display list, including portable commands and clips.
timestamp of this actual presentation, independent of extra host frames used for hover convergence.
positive resolved integer GUI scale, applied only to native target allocation.
Throws
when validation, capture, allocation, or cleanup fails, preserving the primary exception.