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// This Source Code Form is subject to the terms of the Mozilla Public
// License, v. 2.0. If a copy of the MPL was not distributed with this
import SwiftUI
import MetalKit
import Common
enum MilkyWayRendererError: Error {
case failedToCreateCommandQueue
case missingShaderFunction(name: String)
}
class MilkyWayRenderer: NSObject, MTKViewDelegate {
// MARK: – Logger
private var logger: Logger = DefaultLogger.shared
// MARK: – Properties
private let device: MTLDevice
private let commandQueue: MTLCommandQueue
private let pipelineState: MTLRenderPipelineState
private var time: Float = 0.0
private let timeIncrement: Float = 0.0045
private var previousFrameTexture: MTLTexture?
// MARK: – Init
init(device: MTLDevice = MTLCreateSystemDefaultDevice()!) throws {
self.device = device
// Command queue
guard let queue = device.makeCommandQueue() else {
logger.log(
"Failed to create Metal command queue",
level: .fatal,
category: .onboarding
)
throw MilkyWayRendererError.failedToCreateCommandQueue
}
self.commandQueue = queue
// Shader functions
let library = try device.makeDefaultLibrary(bundle: .module)
guard
let vfn = library.makeFunction(name: "milky_way_vertex"),
let ffn = library.makeFunction(name: "milky_way_fragment")
else {
let msg = "Missing shader functions milky_way_vertex / milky_way_fragment"
logger.log(msg, level: .fatal, category: .onboarding)
throw MilkyWayRendererError.missingShaderFunction(name: msg)
}
// Pipeline
let pd = MTLRenderPipelineDescriptor()
pd.vertexFunction = vfn
pd.fragmentFunction = ffn
pd.colorAttachments[0].pixelFormat = .bgra8Unorm
self.pipelineState = try device.makeRenderPipelineState(descriptor: pd)
super.init()
logger.log(
"MilkyWayRenderer initialized successfully",
level: .info,
category: .onboarding
)
}
// MARK: – MTKViewDelegate
func mtkView(_ view: MTKView, drawableSizeWillChange size: CGSize) {
createPreviousFrameTexture(size: size)
}
func draw(in view: MTKView) {
// Acquire drawable
guard let drawable = view.currentDrawable else {
logger.log(
"No currentDrawable available",
level: .warning,
category: .onboarding
)
return
}
// Acquire render pass descriptor
guard let rpd = view.currentRenderPassDescriptor else {
logger.log(
"No currentRenderPassDescriptor",
level: .warning,
category: .onboarding
)
return
}
// Make command buffer
guard let cmdBuf = commandQueue.makeCommandBuffer() else {
logger.log(
"Failed to create commandBuffer",
level: .warning,
category: .onboarding
)
return
}
// Resize history texture if needed
if previousFrameTexture?.width != Int(view.drawableSize.width) ||
previousFrameTexture?.height != Int(view.drawableSize.height) {
createPreviousFrameTexture(size: view.drawableSize)
}
// Encode draw commands
guard let encoder = cmdBuf.makeRenderCommandEncoder(descriptor: rpd) else {
logger.log(
"Failed to create renderCommandEncoder",
level: .warning,
category: .onboarding
)
return
}
encoder.setRenderPipelineState(pipelineState)
encoder.setFragmentBytes(&time,
length: MemoryLayout<Float>.size,
index: 0)
encoder.setFragmentTexture(previousFrameTexture,
index: 0)
encoder.drawPrimitives(type: .triangleStrip,
vertexStart: 0,
vertexCount: 4)
encoder.endEncoding()
// Blit into history
copyCurrentFrameToPrevious(drawable: drawable,
commandBuffer: cmdBuf)
// Present & commit
cmdBuf.present(drawable)
cmdBuf.commit()
// Advance time
time += timeIncrement
}
// MARK: – Helpers
private func createPreviousFrameTexture(size: CGSize) {
let desc = MTLTextureDescriptor.texture2DDescriptor(
pixelFormat: .bgra8Unorm,
width: Int(size.width),
height: Int(size.height),
mipmapped: false
)
desc.usage = [.shaderRead, .renderTarget]
previousFrameTexture = device.makeTexture(descriptor: desc)
}
private func copyCurrentFrameToPrevious(drawable: CAMetalDrawable,
commandBuffer: MTLCommandBuffer) {
guard let history = previousFrameTexture else { return }
let blit = commandBuffer.makeBlitCommandEncoder()
blit?.copy(
from: drawable.texture,
sourceSlice: 0,
sourceLevel: 0,
sourceOrigin: MTLOrigin(x: 0, y: 0, z: 0),
sourceSize: MTLSize(
width: history.width,
height: history.height,
depth: 1
),
to: history,
destinationSlice: 0,
destinationLevel: 0,
destinationOrigin: MTLOrigin(x: 0, y: 0, z: 0)
)
blit?.endEncoding()
}
}
// MARK: – SwiftUI Bridge
struct MilkyWayMetalView: UIViewRepresentable {
func makeUIView(context: Context) -> MTKView {
let view = MTKView()
view.device = MTLCreateSystemDefaultDevice()
view.framebufferOnly = false
view.colorPixelFormat = .bgra8Unorm
view.delegate = context.coordinator
return view
}
func updateUIView(_ uiView: MTKView, context: Context) { }
func makeCoordinator() -> MilkyWayRenderer {
do {
return try MilkyWayRenderer()
} catch {
// If init fails here, it’s truly unrecoverable
DefaultLogger.shared.log(
"Fatal: could not instantiate MilkyWayRenderer – \(error)",
level: .fatal,
category: .onboarding
)
fatalError("MilkyWayRenderer init failed: \(error)")
}
}
}
struct MetalView_Previews: PreviewProvider {
static var previews: some View {
MilkyWayMetalView()
.edgesIgnoringSafeArea(.all)
}
}