retainedGuiResourceSetCount
Reports separately budgeted portable GUI resource sets across every registered native device.
The sum includes active, retired, partially initialized, quarantined, and asynchronously destroying sets. It neither polls nor invokes a native API, is safe after terminal shutdown, and does not change Canvas target accounting.
Return
the current portable-set permit count, or zero when all registered devices have released their resources.
Throws
off the registry owner thread.
if the sum cannot be represented as an Int.