Gets some uniforms in on the action.

With some effort towards scans, but incompletely so.

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

@@ -10,16 +10,26 @@
 
 #import <Metal/Metal.h>
 
+namespace {
+
+struct Uniforms {
+	int32_t scale[2];
+	float lineWidth;
+};
+
+}
+
 @implementation CSScanTarget {
 	id<MTLCommandQueue> _commandQueue;
 
-	// TEST ONLY: to check that I'm drawing _something_, I'm heading towards ye standard
-	// Gouraud shading triangle. https://metalbyexample.com/up-and-running-2/ is providing
-	// much of the inspiration, albeit that I'm proceeding via MKLView.
 	id<MTLFunction> _vertexShader;
 	id<MTLFunction> _fragmentShader;
-	id<MTLBuffer> _verticesBuffer;
 	id<MTLRenderPipelineState> _gouraudPipeline;
+
+	// Buffers.
+	id<MTLBuffer> _quadBuffer;		// i.e. four vertices defining a quad.
+	id<MTLBuffer> _uniformsBuffer;
+	id<MTLBuffer> _scansBuffer;
 }
 
 - (nonnull instancetype)initWithView:(nonnull MTKView *)view {
@@ -27,42 +37,35 @@
 	if(self) {
 		_commandQueue = [view.device newCommandQueue];
 
-		// Generate some static buffers. AS A TEST.
+		// Install the standard quad.
 		constexpr float vertices[] = {
-			-0.9f,	-0.9f,			// Position.
-			1.0f, 	0.0f, 	0.0f,	// Colour.
-
+			-0.9f,	-0.9f,
 			-0.9f,	0.9f,
-			0.0f, 	1.0f, 	0.0f,
-
 			0.9f,	-0.9f,
-			0.0f, 	0.0f, 	1.0f,
-
 			0.9f,	0.9f,
-			0.0f, 	1.0f, 	1.0f,
 		};
-		_verticesBuffer = [view.device newBufferWithBytes:vertices length:sizeof(vertices) options:MTLResourceOptionCPUCacheModeDefault];
+		_quadBuffer = [view.device newBufferWithBytes:vertices length:sizeof(vertices) options:MTLResourceCPUCacheModeDefaultCache];
 
+		// Allocate space for uniforms.
+		_uniformsBuffer = [view.device newBufferWithLength:16 options:MTLResourceCPUCacheModeWriteCombined];
+		Uniforms testUniforms = {
+			.scale = {0, 0},
+			.lineWidth = 0.1f
+		};
+		[self setUniforms:testUniforms];
+
+		// The quad buffer has only 2d positions.
 		MTLVertexDescriptor *vertexDescriptor = [[MTLVertexDescriptor alloc] init];
-
-		// Position.
 		vertexDescriptor.attributes[0].bufferIndex = 0;
 		vertexDescriptor.attributes[0].offset = 0;
 		vertexDescriptor.attributes[0].format = MTLVertexFormatFloat2;
-
-		// Colour.
-		vertexDescriptor.attributes[1].bufferIndex = 0;
-		vertexDescriptor.attributes[1].offset = sizeof(float)*2;
-		vertexDescriptor.attributes[1].format = MTLVertexFormatFloat3;
-
-		// Total vertex size.
-		vertexDescriptor.layouts[0].stride = sizeof(float)*5;
+		vertexDescriptor.layouts[0].stride = sizeof(float)*2;
 
 		// Generate TEST pipeline.
 		id<MTLLibrary> library = [view.device newDefaultLibrary];
 		MTLRenderPipelineDescriptor *pipelineDescriptor = [[MTLRenderPipelineDescriptor alloc] init];
-		pipelineDescriptor.vertexFunction = [library newFunctionWithName:@"vertex_main"];
-		pipelineDescriptor.fragmentFunction = [library newFunctionWithName:@"fragment_main"];
+		pipelineDescriptor.vertexFunction = [library newFunctionWithName:@"scanVertexMain"];
+		pipelineDescriptor.fragmentFunction = [library newFunctionWithName:@"scanFragmentMain"];
 		pipelineDescriptor.colorAttachments[0].pixelFormat = view.colorPixelFormat;
 		pipelineDescriptor.vertexDescriptor = vertexDescriptor;
 		_gouraudPipeline = [view.device newRenderPipelineStateWithDescriptor:pipelineDescriptor error:nil];
@@ -70,6 +73,11 @@
 	return self;
 }
 
+- (void)setUniforms:(const Uniforms &)uniforms {
+	memcpy(_uniformsBuffer.contents, &uniforms, sizeof(Uniforms));
+//	[_uniformsBuffer didModifyRange:NSMakeRange(0, sizeof(Uniforms))];
+}
+
 /*!
  @method mtkView:drawableSizeWillChange:
  @abstract Called whenever the drawableSize of the view will change
@@ -95,7 +103,10 @@
 
 	// Drawing. Just the test triangle, as described above.
 	[encoder setRenderPipelineState:_gouraudPipeline];
-	[encoder setVertexBuffer:_verticesBuffer offset:0 atIndex:0];
+
+	[encoder setVertexBuffer:_quadBuffer offset:0 atIndex:0];
+	[encoder setVertexBuffer:_uniformsBuffer offset:0 atIndex:1];
+
 	[encoder drawPrimitives:MTLPrimitiveTypeTriangleStrip vertexStart:0 vertexCount:4 instanceCount:1];
 
 	// Complete encoding.

OSBindings/Mac/Clock Signal/ScanTarget/ScanTarget.metal

@@ -12,23 +12,52 @@ using namespace metal;
 // These two structs are the same, but defined separately as an artefact
 // of my learning process, and the fact that they soon won't be.
 
-struct InputVertex {
+struct Uniforms {
+	// This is used to scale scan positions, i.e. it provides the range
+	// for mapping from scan-style integer positions into eye space.
+	int2 scale						[[attribute(0)]];
+
+	// This provides the intended width of a scan, in eye-coordinate terms.
+	float lineWidth					[[attribute(1)]];
+};
+
+// This is intended to match `Scan` as defined by the BufferingScanTarget.
+// Fields have been combined as necessary to make them all at least four
+// bytes in size, since that is the required attribute alignment in Swift.
+struct Scan {
+	uint32_t startPosition			[[attribute(0)]];
+	uint32_t startOffsetAndAngle	[[attribute(1)]];
+	uint32_t startCycles			[[attribute(2)]];
+
+	uint32_t endPosition			[[attribute(3)]];
+	uint32_t endOffsetAndAngle		[[attribute(4)]];
+	uint32_t endCycles				[[attribute(5)]];
+
+	uint32_t compositeAmplitude		[[attribute(6)]];
+	uint32_t dataYAndLine			[[attribute(7)]];
+};
+
+// This is a custom thing defining one corner of a quad.
+struct QuadInputVertex {
 	float2 position	[[attribute(0)]];
-	float3 colour	[[attribute(1)]];
 };
 
 struct ColouredVertex {
 	float4 position [[position]];
-	float4 colour;
 };
 
-vertex ColouredVertex vertex_main(InputVertex vert [[stage_in]]) {
+
+// MARK: - Scan shaders; these do final output to the display.
+
+vertex ColouredVertex scanVertexMain(	QuadInputVertex vert [[stage_in]],
+										constant Uniforms &uniforms [[buffer(1)]],
+										constant Scan *scans [[buffer(2)]],
+										ushort instance [[instance_id]]) {
 	ColouredVertex output;
-	output.position = float4(vert.position, 0.0, 1.0);
-	output.colour = float4(vert.colour, 1.0);
+	output.position = float4(vert.position * uniforms.lineWidth, 0.0, 1.0);
 	return output;
 }
 
-fragment float4 fragment_main(ColouredVertex vert [[stage_in]]) {
-	return vert.colour;
+fragment float4 scanFragmentMain(ColouredVertex vert [[stage_in]]) {
+	return float4(1.0);
 }