No HDR / EDR: the framebuffer offers 8 bits per channel only #7

openarea:displaykind:upstreamseverity:lowfound-by:featuretestkind:feature

watchthelight 2026-10-18

NSScreen.maximumPotentialExtendedDynamicRangeColorComponentValue is 1.0 and the screen depth is 24 bits per pixel. NVRMFB publishes only IO32BitDirectPixels (8 bpc), so there is no HDR or EDR on the internal panel (upstream #30). This is recorded for the feature matrix, not as a defect of the fork.

Tested on RTX 5070 Laptop (GB206, 10DE:2D18), Lenovo Legion 5 15IAX10, macOS 26.7.1 (25G241), stock 2.3.7. Evidence: project-legion evidence/native/featuretest-2026-10-18/A/disp.edr.txt.

watchthelight 2026-10-27

A report in nullmoth/nvidia-macos-driver#341 narrows down why 10-bit never shows up: CoreDisplay takes the vendor from the framebuffer class name, and a name containing "NVDA" gets force8BPC = YES. Advertising 10 bpc, BT.2020 and HDR10 left SupportsHDRMode false. Renaming the class cleared the flag, but WindowServer then lost its Metal compositor and aborted.

So the pixel format alone was never going to be enough, which matches what our 30-bit boots showed. Not reproduced here yet.

Write-up: https://github.com/watchthelight-labs/research/blob/main/scout/nvgfx/2026-10-27.md

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