How has the Metal framework been upgraded to boost graphics rendering, and what new functionalities should developers focus on for creating high-performance games?

The Metal framework has received several significant upgrades to boost graphics rendering and provide new functionalities for developers creating high-performance games. Here are the key enhancements:

1. Unified Metal Shaders: Developers can now compile their shaders once and deploy them across both macOS and iOS, simplifying the development process (Port advanced games to Apple platforms).

2. Metal Device Initialization: The initialization process is now unified, allowing the same creation API to be used for both macOS and iOS. Additionally, the device certification API helps scale the game's configuration by querying devices for performance profiles (Port advanced games to Apple platforms).

3. Game Mode on iOS: iOS now includes a game mode that reduces background activity and Bluetooth latency, improving input and headphone responsiveness. Developers can opt into this mode by adding the GCSupportsGameMode key in the iOS info plist (Port advanced games to Apple platforms).

4. MetalFX Upscaling: MetalFX allows for significant performance improvements by scaling a lower resolution image up to the target output resolution more efficiently. This year, a new reactive mask feature has been added to achieve higher upscaling fidelity in scenes with fast-moving objects (Port advanced games to Apple platforms).

5. Debugging and Profiling HLSL Shaders: Xcode now supports debugging and profiling the source of original HLSL shaders at any stage of the development process, whether evaluating the original Windows binary or debugging the Metal version of the game (Platforms State of the Union).

6. Gameporting Toolkit 2: This toolkit includes updates to help developers bring more advanced games to Mac, iPad, and iPhone. It supports improved compatibility with technologies like AVX2 and advanced gaming features like ray tracing (Platforms State of the Union).

7. Resource Residency: Metal now includes improvements for resource residency, allowing for better management of GPU memory and resources (Port advanced games to Apple platforms).

Developers should focus on these new functionalities to create high-performance games that leverage the full capabilities of the Metal framework and Apple devices. For more detailed guidance, refer to the sessions "Port advanced games to Apple platforms" and "Platforms State of the Union" from WWDC 2024.