Oracle confirmed the separate-window glass mode WAS fast and tanked ~2 builds
back, so the regression is real and expresses only on his machine. This names
the cost from inside his own session log:
[glassperf] ticks=N tickMs=T | <window> n=paints ms=cost | ...
tickMs is the synchronous UpdateWindow sweep measured INSIDE the render frame
(L4VIDEO calls the tick), so on a machine where GDI serialises against D3D
present it IS the per-frame tax, and the per-window split names the panel.
Each WM_PAINT is QPC-timed at the dispatch chokepoint (the HALFTONE
StretchDIBits whose cost is driver-dependent). Default ON like [segperf];
BT_PERF_LOG=0 opts out. Smoke-tested: lines live in a 60s panel run.
Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_018SgmXGNMXavXiafKXf9MDC