Swiftgram/submodules/TelegramUI/Components/Calls/CallScreen/Sources/CallScreen.swift

import Foundation
import UIKit
import Display
import MetalKit

private final class BundleMarker: NSObject {
}

private var metalLibraryValue: MTLLibrary?
func metalLibrary(device: MTLDevice) -> MTLLibrary? {
    if let metalLibraryValue {
        return metalLibraryValue
    }
    
    let mainBundle = Bundle(for: BundleMarker.self)
    guard let path = mainBundle.path(forResource: "CallScreenMetalSourcesBundle", ofType: "bundle") else {
        return nil
    }
    guard let bundle = Bundle(path: path) else {
        return nil
    }
    guard let library = try? device.makeDefaultLibrary(bundle: bundle) else {
        return nil
    }
    
    metalLibraryValue = library
    return library
}