Exclude software-dimming overlay windows from screen capture#1877
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cgchiroyasu-dev wants to merge 2 commits into
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Exclude software-dimming overlay windows from screen capture#1877cgchiroyasu-dev wants to merge 2 commits into
cgchiroyasu-dev wants to merge 2 commits into
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For displays without DDC or gamma support (e.g. DisplayLink / virtual displays), MonitorControl dims via a full-screen black 'shade' NSWindow. Because the shade window's sharingType defaults to .readOnly, it is captured by screenshots and screen recordings, so any capture taken while a display is dimmed comes out darkened (see discussions MonitorControl#1453, MonitorControl#866, MonitorControl#1446). Set sharingType = .none on the shade windows and the gamma activity enforcer so they no longer appear in screen captures. This is display-only chrome; excluding it from capture does not change what the user sees on screen.
Virtual displays (AirPlay/Sidecar/DisplayLink) are themselves presented to the physical monitor via screen capture. Setting sharingType=.none on their shade would remove the dimming from the actual monitor, not just from screenshots. Guard the opt-out with !isVirtual so DisplayLink etc. keep dimming, while real displays using shade (e.g. Mac mini HDMI) still get screenshot-clean dimming.
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Problem
When a display is dimmed using software dimming (the black "shade" overlay), screenshots and screen recordings of that display come out darkened — the capture includes the dimming overlay. This is most visible on displays that have no DDC and no gamma support, such as DisplayLink / virtual displays, where the shade overlay is the only dimming mechanism available.
Reported in:
Root cause
DisplayManager.createShadeOnDisplay(...)creates a full‑screen blackNSWindowto act as the dimming shade, but never sets itssharingType. The default is.readOnly, so the shade window is visible to the screen‑capture system (CGWindowList/ ScreenCaptureKit). Any screenshot or recording taken while a display is dimmed therefore captures the shade and looks dark. The same applies to the 1×1gammaActivityEnforcerhelper window.Fix
Set
sharingType = .noneon the shade windows and the gamma activity enforcer. These windows are display‑only chrome; excluding them from capture does not change what the user sees on screen — the display stays visibly dimmed, but captures are taken from the content underneath.Verification (macOS 15, DisplayLink displays)
Enumerated MonitorControl's on‑screen windows via
CGWindowListCopyWindowInfoand readkCGWindowSharingState:1(ReadOnly → captured)0(None → excluded)1(captured)0(excluded)With the fix, the dimmed display still looks dimmed to the eye, but
screencaptureof that display no longer includes the shade — screenshots come out at normal brightness. An isolated test window withsharingType = .noneconfirmed it is excluded from capture (content behind shows through) rather than rendered black.No behavior change for users who don't use software dimming.