debugOverprintCompositing property

@visibleForTesting bool debugOverprintCompositing

Overprint fallback-compositing kill switch (the A/B baseline is "off"). Off, setOverprint still records the state but fills/strokes composite normally, exactly as before overprint was consumed.

This governs only the RGB stand-in below. Faithful overprint is resolved upstream in the interpreter's colorant buffer (issue #502), which hands this device an already-composited colour with the overprint flag cleared; PdfInterpreter.debugResolveOverprint is that path's switch.

Implementation

@visibleForTesting
static bool debugOverprintCompositing = true;