This MVP Metal main.swift shows up blank - swift

Question

So in a main.swift file in your project, you can create a window (and go from there) like this:
let nsapp = NSApplication.shared
let window = NSWindow(
contentRect: NSMakeRect(0, 0, 200, 200),
styleMask: .fullSizeContentView,
backing: NSWindow.BackingStoreType.buffered,
defer: false
)
window.cascadeTopLeft(from:NSMakePoint(20,20))
nsapp.run()
I'm wondering how to do the same thing but with a Metal triangle. I've been looking through github.com/topics/metalkit but the closest thing I've found so far wasn't there but in a gist.
import Cocoa
import MetalKit
#NSApplicationMain
class AppDelegate: NSObject, NSApplicationDelegate, MTKViewDelegate {
weak var window: NSWindow!
weak var metalView: MTKView!
let device = MTLCreateSystemDefaultDevice()!
var commandQueue: MTLCommandQueue!
var pipelineState: MTLRenderPipelineState!
func applicationDidFinishLaunching(_ aNotification: Notification) {
metalView = MTKView(frame: NSRect(origin: CGPoint.zero, size: window.frame.size), device: device)
metalView.delegate = self
window.contentView = metalView
commandQueue = device.makeCommandQueue()
let shaders = """
#include <metal_stdlib>
using namespace metal;
struct VertexIn {
packed_float3 position;
packed_float3 color;
};
struct VertexOut {
float4 position [[position]];
float4 color;
};
vertex VertexOut vertex_main(device const VertexIn *vertices [[buffer(0)]],
uint vertexId [[vertex_id]]) {
VertexOut out;
out.position = float4(vertices[vertexId].position, 1);
out.color = float4(vertices[vertexId].color, 1);
return out;
}
fragment float4 fragment_main(VertexOut in [[stage_in]]) {
return in.color;
}
"""
do {
let library = try device.makeLibrary(source: shaders, options: nil)
let pipelineDescriptor = MTLRenderPipelineDescriptor()
pipelineDescriptor.colorAttachments[0].pixelFormat = metalView.colorPixelFormat
pipelineDescriptor.vertexFunction = library.makeFunction(name: "vertex_main")
pipelineDescriptor.fragmentFunction = library.makeFunction(name: "fragment_main")
pipelineState = try device.makeRenderPipelineState(descriptor: pipelineDescriptor)
} catch {}
}
func mtkView(_ view: MTKView, drawableSizeWillChange size: CGSize) {
}
func draw(in view: MTKView) {
guard let commandBuffer = commandQueue.makeCommandBuffer() else { return }
guard let passDescriptor = view.currentRenderPassDescriptor else { return }
guard let encoder = commandBuffer.makeRenderCommandEncoder(descriptor: passDescriptor) else { return }
let vertexData: [Float] = [ -0.5, -0.5, 0, 1, 0, 0,
0.5, -0.5, 0, 0, 1, 0,
0, 0.5, 0, 0, 0, 1 ]
encoder.setVertexBytes(vertexData, length: vertexData.count * MemoryLayout<Float>.stride, index: 0)
encoder.setRenderPipelineState(pipelineState)
encoder.drawPrimitives(type: .triangle, vertexStart: 0, vertexCount: 3)
encoder.endEncoding()
commandBuffer.present(view.currentDrawable!)
commandBuffer.commit()
}
}
It at least builds an MTKView from scratch. But I'm not sure yet what the minimum viable product is for getting a metal thing working without any controllers, delegates, applications, I'm going to start just doing trial and error to get it working but it's going to probably take a few days and thought it might be helpful for others if someone's already figured this out.
I have combined the two but it isn't rendering anything from what I can tell.
import AVFoundation
import AudioToolbox
import Foundation
import QuartzCore
import Security
import WebKit
import Cocoa
import Metal
import MetalKit
import Swift
let device = MTLCreateSystemDefaultDevice()!
// Our clear color, can be set to any color
let clearColor = MTLClearColor(red: 0.1, green: 0.57, blue: 0.25, alpha: 1)
let nsapp = NSApplication.shared
let appName = ProcessInfo.processInfo.processName
let window = NSWindow(
contentRect: NSMakeRect(0, 0, 1000, 1000),
styleMask: .fullSizeContentView,
backing: NSWindow.BackingStoreType.buffered,
defer: false
)
window.cascadeTopLeft(from:NSMakePoint(20,20))
window.title = appName;
window.makeKeyAndOrderFront(nil)
struct Vertex {
var position: float3
var color: float4
}
let view = MTKView(frame: NSRect(origin: CGPoint.zero, size: window.frame.size), device: device)
window.contentView = view
view.device = device
view.colorPixelFormat = .bgra8Unorm
view.clearColor = clearColor
let queue = device.makeCommandQueue()!
var vertexBuffer: MTLBuffer!
var vertices: [Vertex] = [
Vertex(position: float3(0,1,0), color: float4(1,0,0,1)),
Vertex(position: float3(-1,-1,0), color: float4(0,1,0,1)),
Vertex(position: float3(1,-1,0), color: float4(0,0,1,1))
]
let shaders = """
#include <metal_stdlib>
using namespace metal;
// Basic Struct to match our Swift type
// This is what is passed into the Vertex Shader
struct VertexIn {
float3 position;
float4 color;
};
// What is returned by the Vertex Shader
// This is what is passed into the Fragment Shader
struct VertexOut {
float4 position [[ position ]];
float4 color;
};
vertex VertexOut basic_vertex_function(const device VertexIn *vertices [[ buffer(0) ]],
uint vertexID [[ vertex_id ]]) {
VertexOut vOut;
vOut.position = float4(vertices[vertexID].position,1);
vOut.color = vertices[vertexID].color;
return vOut;
}
fragment float4 basic_fragment_function(VertexOut vIn [[ stage_in ]]) {
return vIn.color;
}
"""
let library = try device.makeLibrary(source: shaders, options: nil)
let pipelineDescriptor = MTLRenderPipelineDescriptor()
pipelineDescriptor.colorAttachments[0].pixelFormat = .bgra8Unorm
pipelineDescriptor.vertexFunction = library.makeFunction(name: "basic_vertex_function")
pipelineDescriptor.fragmentFunction = library.makeFunction(name: "basic_fragment_function")
let pipelineState = try device.makeRenderPipelineState(descriptor: pipelineDescriptor)
vertexBuffer = device.makeBuffer(
bytes: vertices,
length: MemoryLayout<Vertex>.stride * vertices.count,
options: []
)
enum MetalErrors: Error {
case commandBuffer
case passDescriptor
case encoder
}
guard let drawable = view.currentDrawable else { throw MetalErrors.commandBuffer }
guard let commandBuffer = queue.makeCommandBuffer() else { throw MetalErrors.commandBuffer }
guard let passDescriptor = view.currentRenderPassDescriptor else { throw MetalErrors.passDescriptor }
guard let encoder = commandBuffer.makeRenderCommandEncoder(descriptor: passDescriptor) else { throw MetalErrors.encoder }
nsapp.run()
// let vertexData: [Float] = [ -0.5, -0.5, 0, 1, 0, 0,
// 0.5, -0.5, 0, 0, 1, 0,
// 0, 0.5, 0, 0, 0, 1 ]
encoder.setRenderPipelineState(pipelineState)
// encoder.setVertexBytes(vertexData, length: vertexData.count * MemoryLayout<Float>.stride, index: 0)
encoder.drawPrimitives(type: .triangle, vertexStart: 0, vertexCount: vertices.count)
encoder.endEncoding()
commandBuffer.present(drawable)
commandBuffer.commit()
It's blank for me. I tried following this as well.
This is getting closer.

Answer 1

The main problem here is that NSApplication's run method doesn't return until the app terminates, so your render command encoding never happens. You can subclass MTKView and override its draw method to do your drawing instead:
import Cocoa
import MetalKit
let device = MTLCreateSystemDefaultDevice()!
// Our clear color, can be set to any color
let clearColor = MTLClearColor(red: 0.1, green: 0.57, blue: 0.25, alpha: 1)
let shaders = """
#include <metal_stdlib>
using namespace metal;
// Basic Struct to match our Swift type
// This is what is passed into the Vertex Shader
struct VertexIn {
float3 position;
float4 color;
};
// What is returned by the Vertex Shader
// This is what is passed into the Fragment Shader
struct VertexOut {
float4 position [[ position ]];
float4 color;
};
vertex VertexOut basic_vertex_function(const device VertexIn *vertices [[ buffer(0) ]],
uint vertexID [[ vertex_id ]]) {
VertexOut vOut;
vOut.position = float4(vertices[vertexID].position,1);
vOut.color = vertices[vertexID].color;
return vOut;
}
fragment float4 basic_fragment_function(VertexOut vIn [[ stage_in ]]) {
return vIn.color;
}
"""
let library = try device.makeLibrary(source: shaders, options: nil)
let pipelineDescriptor = MTLRenderPipelineDescriptor()
pipelineDescriptor.colorAttachments[0].pixelFormat = .bgra8Unorm
pipelineDescriptor.vertexFunction = library.makeFunction(name: "basic_vertex_function")
pipelineDescriptor.fragmentFunction = library.makeFunction(name: "basic_fragment_function")
let pipelineState = try device.makeRenderPipelineState(descriptor: pipelineDescriptor)
struct Vertex {
var position: float3
var color: float4
}
let queue = device.makeCommandQueue()!
var vertexBuffer: MTLBuffer!
var vertices: [Vertex] = [
Vertex(position: float3(0,1,0), color: float4(1,0,0,1)),
Vertex(position: float3(-1,-1,0), color: float4(0,1,0,1)),
Vertex(position: float3(1,-1,0), color: float4(0,0,1,1))
]
vertexBuffer = device.makeBuffer(
bytes: vertices,
length: MemoryLayout<Vertex>.stride * vertices.count,
options: []
)
enum MetalErrors: Error {
case commandBuffer
case passDescriptor
case encoder
}
class MyMTKView : MTKView {
override func draw() {
guard let drawable = currentDrawable else { return }
guard let passDescriptor = currentRenderPassDescriptor else { return }
guard let commandBuffer = queue.makeCommandBuffer() else { return }
guard let encoder = commandBuffer.makeRenderCommandEncoder(descriptor: passDescriptor) else { return }
encoder.setRenderPipelineState(pipelineState)
encoder.setVertexBuffer(vertexBuffer, offset: 0, index: 0 )
encoder.drawPrimitives(type: .triangle, vertexStart: 0, vertexCount: vertices.count)
encoder.endEncoding()
commandBuffer.present(drawable)
commandBuffer.commit()
}
}
let nsapp = NSApplication.shared
let appName = ProcessInfo.processInfo.processName
let window = NSWindow(
contentRect: NSMakeRect(0, 0, 1000, 1000),
styleMask: [.titled, .closable, .resizable],
backing: NSWindow.BackingStoreType.buffered,
defer: false
)
window.cascadeTopLeft(from:NSMakePoint(20,20))
window.title = appName;
let view = MyMTKView(frame: NSRect(origin: CGPoint.zero, size: window.frame.size), device: device)
window.contentView = view
view.device = device
view.colorPixelFormat = .bgra8Unorm
view.clearColor = clearColor
window.makeKeyAndOrderFront(nil)
nsapp.run()