This is possibly at least dispatching an empty command buffer correctly.

OSBindings/Mac/Clock Signal/ScanTarget/CSScanTarget.h

@@ -7,12 +7,13 @@
 //
 
 #import <Foundation/Foundation.h>
+#import <MetalKit/MetalKit.h>
 
 /*!
 	Provides a ScanTarget that uses Metal as its back-end.
 */
-@interface CSScanTarget : NSObject
+@interface CSScanTarget : NSObject <MTKViewDelegate>
 
-- (nonnull instancetype)init;
+- (nonnull instancetype)initWithView:(nonnull MTKView *)view;
 
 @end

OSBindings/Mac/Clock Signal/ScanTarget/CSScanTarget.mm

@@ -11,18 +11,47 @@
 #import <Metal/Metal.h>
 
 @implementation CSScanTarget {
-	id<MTLDevice> _device;
 	id<MTLCommandQueue> _commandQueue;
 }
 
-- (nonnull instancetype)init {
+- (nonnull instancetype)initWithView:(nonnull MTKView *)view {
 	self = [super init];
 	if(self) {
-		_device = MTLCreateSystemDefaultDevice();
-		_commandQueue = [_device newCommandQueue];
-		NSLog(@"%@; %@", _device, _commandQueue);
+		_commandQueue = [view.device newCommandQueue];
 	}
 	return self;
 }
 
+/*!
+ @method mtkView:drawableSizeWillChange:
+ @abstract Called whenever the drawableSize of the view will change
+ @discussion Delegate can recompute view and projection matricies or regenerate any buffers to be compatible with the new view size or resolution
+ @param view MTKView which called this method
+ @param size New drawable size in pixels
+ */
+- (void)mtkView:(nonnull MTKView *)view drawableSizeWillChange:(CGSize)size {
+	NSLog(@"New size: %@", NSStringFromSize(size));
+}
+
+/*!
+ @method drawInMTKView:
+ @abstract Called on the delegate when it is asked to render into the view
+ @discussion Called on the delegate when it is asked to render into the view
+ */
+- (void)drawInMTKView:(nonnull MTKView *)view {
+	id <MTLCommandBuffer> commandBuffer = [_commandQueue commandBuffer];
+	MTLRenderPassDescriptor *const descriptor = view.currentRenderPassDescriptor;
+	id <MTLRenderCommandEncoder> encoder = [commandBuffer renderCommandEncoderWithDescriptor:descriptor];
+
+	// TODO: the drawing (!)
+
+	[encoder endEncoding];
+
+	// "Register the drawable's presentation".
+	[commandBuffer presentDrawable:view.currentDrawable];
+
+	// Finalise and commit.
+	[commandBuffer commit];
+}
+
 @end

OSBindings/Mac/Clock Signal/Views/CSScanTargetView.m

@@ -8,6 +8,7 @@
 
 #import "CSScanTargetView.h"
 #import "CSApplication.h"
+#import "CSScanTarget.h"
 @import CoreVideo;
 @import GLKit;
 
@@ -27,6 +28,8 @@
 
 	atomic_int _isDrawingFlag;
 	BOOL _isInvalid;
+
+	CSScanTarget *_scanTarget;
 }
 
 //- (void)prepareOpenGL {
@@ -120,9 +123,10 @@ static CVReturn DisplayLinkCallback(__unused CVDisplayLinkRef displayLink, const
 	[self redrawWithEvent:CSScanTargetViewRedrawEventTimer];
 }
 
-- (void)drawRect:(NSRect)dirtyRect {
-	[self redrawWithEvent:CSScanTargetViewRedrawEventAppKit];
-}
+//- (void)drawRect:(NSRect)dirtyRect {
+//	[self redrawWithEvent:CSScanTargetViewRedrawEventAppKit];
+//	NSLog(@"...");
+//}
 
 - (void)redrawWithEvent:(CSScanTargetViewRedrawEvent)event  {
 	[self performWithGLContext:^{
@@ -179,6 +183,13 @@ static CVReturn DisplayLinkCallback(__unused CVDisplayLinkRef displayLink, const
 //}
 
 - (void)awakeFromNib {
+	// Use the preferred device if available.
+	if(@available(macOS 10.15, *)) {
+		self.device = self.preferredDevice;
+	} else {
+		self.device = MTLCreateSystemDefaultDevice();
+	}
+
 //	NSOpenGLPixelFormatAttribute attributes[] = {
 //		NSOpenGLPFADoubleBuffer,
 //		NSOpenGLPFAOpenGLProfile,	NSOpenGLProfileVersion3_2Core,
@@ -203,6 +214,9 @@ static CVReturn DisplayLinkCallback(__unused CVDisplayLinkRef displayLink, const
 //	self.pixelFormat = pixelFormat;
 //	self.openGLContext = context;
 //	self.wantsBestResolutionOpenGLSurface = YES;
+	// Create the scan target.
+	_scanTarget = [[CSScanTarget alloc] initWithView:self];
+	self.delegate = _scanTarget;
 
 	// Register to receive dragged and dropped file URLs.
 	[self registerForDraggedTypes:@[(__bridge NSString *)kUTTypeFileURL]];