Minecraft: Bedrock Edition on Windows doesn't opt in for Screen Tearing causing V-Sync Off to not behave correctly.

Examples:

• Game FPS capped 2x the refresh rate.
• Capped FPS in fullscreen but Uncapped in windowed.

The root issue seems to be how the game is requesting V-Sync to be turned off.

By using PresentMon, a tool that allows us to see performance metrics of a graphical application we can see how IDXGISwapChain::Present() is being called.
Make sure to download their CLI tool & not their installer for PresentMon!

Using the following command in an admin Command Prompt window with gfx_vsync set to 0 disable V-Sync ingame:

presentmon.exe -no_csv -process_name Minecraft.Windows.exe 

Minecraft: Bedrock Edition internally calls the function as follows:

IDXGISwapChain::Present(0, 0)

Technically this does disable V-Sync but as mentioned before it doesn't behave as intended.

My monitor is 75 Hz & as you can see it's capped double the refresh rate.

Microsoft's Documentation for IDXGISwapchain::Present flags specifically mentions DXGI_PRESENT_ALLOW_TEARING must be used in an windowed application to allow for screen tearing as well as the swapchain having screen tearing support via DXGI_SWAP_CHAIN_FLAG_ALLOW_TEARING.

For demonstration purposes, here is the game modded to add screen tearing support.

This is done by:

• Hooking IDXGISwapchain::Present(), IDXGISwapchain::ResizeBuffers() & IDXGIFactory2::CreateSwapChainForCoreWindow.
• Add screen tearing support via flags as required.

As you can see as soon as we add screen tearing support, V-Sync works as intended.

Additionally this also fixes MCPE-98861 since V-Sync off works as intended.