GeezerVison

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:

• Screenshots come up blank when brightness dimmed #1453 (Screenshots come up blank/dark when brightness dimmed)
• Screenshot from external screen is dimmer when MonitorControl is set to `Avoid gamma table manipulation`? #866 (Screenshot from external screen is dimmer with "Avoid gamma table manipulation")
• Screenshots come up blank when brightness dimmed #1446

Root cause

DisplayManager.createShadeOnDisplay(...) creates a full‑screen black NSWindow to act as the dimming shade, but never sets its sharingType. 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 1×1 gammaActivityEnforcer helper window.

Fix

Set sharingType = .none on 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.

shade.sharingType = .none
self.gammaActivityEnforcer.sharingType = .none

Verification (macOS 15, DisplayLink displays)

Enumerated MonitorControl's on‑screen windows via CGWindowListCopyWindowInfo and read kCGWindowSharingState:

With the fix, the dimmed display still looks dimmed to the eye, but screencapture of that display no longer includes the shade — screenshots come out at normal brightness. An isolated test window with sharingType = .none confirmed it is excluded from capture (content behind shows through) rather than rendered black.

No behavior change for users who don't use software dimming.