[dragoshont]

On my MacBook Pro with an external 60 Hz main display, a VM window on the built-in 120 Hz ProMotion panel never shows more than 60 fps.

The display is drawn from MTKView's own timer, and on that panel the timer stayed at 60 callbacks per second even with preferredFramesPerSecond = 120 (confirmed in lldb). A CAMetalDisplayLink on the same layer runs at the rate it requests, and its frames reach the screen at 120 Hz. I haven't tried a ProMotion Mac without an external display.

On macOS 14+ this drives the renderer from a CAMetalDisplayLink. VMMetalView hands the renderer the drawable from each update, so CSMetalRenderer doesn't change. Behaviour:

• The rate follows the screen the window is on.
• The link pauses while the VM is suspended.
• An FPS limit changed in Settings applies on the next VM start. Before, it applied only when the window was created, and that window is reused across restarts (see Crash (index out of range) starting a VM after its displays are removed: stale Metal display window is reused #7882).
• macOS 12/13 keep the MTKView timer.

Related: #7820. With #7982 the guest itself can also run at 120 Hz.

Testing: macOS 27.0.1, MacBook Pro M5 Max. Debug builds with and without this change, and a disposable Alpine VM whose console scrolls constantly. With the VM window on the 120 Hz panel, I counted distinct frames per second with ScreenCaptureKit and checked them against the Metal HUD:

Build	Window fps (3 runs)	Metal HUD
main	59.9 / 60.0 / 60.1	59.8
this PR	119.6 / 119.9 / 120.1	120.0

Also with this PR:

• Moving the window to the 60 Hz display and back: 59.6, then 119.5 fps.
• Pause and resume work.
• Fullscreen scales correctly at 119.2 fps.
• Closing the window is clean.
• Idle cost rises from 1.5% to 2.1% of a core, because the link ticks at 120 Hz.

Windows 11 Pro ARM64 (build 26300, viogpu3d, D3DMetal), window on the 120 Hz panel and the guest at 120 Hz through #7982. A D3D11 test presenting ~560 fps in the guest:

• Window: 76 fps over 10 s (ScreenCaptureKit, median frame 11.9 ms); Metal HUD 95 fps.
• UTM 5.0.8 on the same panel stayed at or below 60 (58.5 fps in an earlier Hollow Knight run).

The Mac was busy with another app using 3+ cores during the Windows run, so those numbers are noisy. The point is that the window gets past 60.

Not tested yet: macOS 12/13, secondary displays.

An AI agent ran these tests on my Mac.

I have read the AI contribution guidelines and have followed them to the best of my ability.