With Steam's Frame Limit on, gamescope forces FIFO while the WSI layer
always hands the driver MAILBOX, so a game with the eight images the app
asks for could queue up to seven frames ahead of the screen. While the
limiter forces FIFO the layer now uses its default of 3 images; DXVK and
VKD3D-Proton already recreate their swapchain when the limiter changes,
other apps are asked to with VK_SUBOPTIMAL_KHR (0119).
-r fixed gamescope's pacing and limiter rate for the whole session, so a
panel switched to another mode kept the old rate until the next session.
With GAMESCOPE_NESTED_REFRESH_FOLLOWS_HOST=1 the rate the host compositor
reports replaces it, and Steam gets the display information again (0120).
The session sets it whenever it passes -r.
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