feat: add vertex generator in eraser render pass

Memola/Canvas/RenderPasses/EraserRenderPass.swift

@@ -14,12 +14,14 @@ class EraserRenderPass: RenderPass {
     var descriptor: MTLRenderPassDescriptor?
 
     var eraserPipelineState: MTLRenderPipelineState?
+    var quadPipelineState: MTLComputePipelineState?
 
     var stroke: Stroke?
     weak var graphicTexture: MTLTexture?
 
     init(renderer: Renderer) {
         eraserPipelineState = PipelineStates.createEraserPipelineState(from: renderer)
+        quadPipelineState = PipelineStates.createQuadPipelineState(from: renderer)
     }
 
     func resize(on view: MTKView, to size: CGSize, with renderer: Renderer) { }
@@ -27,6 +29,8 @@ class EraserRenderPass: RenderPass {
     func draw(on canvas: Canvas, with renderer: Renderer) {
         guard let descriptor else { return }
 
+        generateVertexBuffer(on: canvas, with: renderer)
+
         guard let commandBuffer = renderer.commandQueue.makeCommandBuffer() else { return }
         commandBuffer.label = "Eraser Command Buffer"
 
@@ -42,4 +46,30 @@ class EraserRenderPass: RenderPass {
         renderEncoder.endEncoding()
         commandBuffer.commit()
     }
+
+    private func generateVertexBuffer(on canvas: Canvas, with renderer: Renderer) {
+        guard let stroke, !stroke.quads.isEmpty, let quadPipelineState else { return }
+        guard let quadCommandBuffer = renderer.commandQueue.makeCommandBuffer() else { return }
+        guard let computeEncoder = quadCommandBuffer.makeComputeCommandEncoder() else { return }
+
+        computeEncoder.label = "Quad Render Pass"
+
+        let quadCount = stroke.quads.endIndex
+        var quads = stroke.quads
+        let quadBuffer = renderer.device.makeBuffer(bytes: &quads, length: MemoryLayout<Quad>.stride * quadCount, options: [])
+        let vertexBuffer = renderer.device.makeBuffer(length: MemoryLayout<QuadVertex>.stride * quadCount * 6, options: [])
+
+        computeEncoder.setComputePipelineState(quadPipelineState)
+        computeEncoder.setBuffer(quadBuffer, offset: 0, index: 0)
+        computeEncoder.setBuffer(vertexBuffer, offset: 0, index: 1)
+
+        stroke.vertexBuffer = vertexBuffer
+
+        let threadsPerGroup = MTLSize(width: 1, height: 1, depth: 1)
+        let numThreadgroups = MTLSize(width: quadCount + 1, height: 1, depth: 1)
+        computeEncoder.dispatchThreadgroups(numThreadgroups, threadsPerThreadgroup: threadsPerGroup)
+        computeEncoder.endEncoding()
+        quadCommandBuffer.commit()
+        quadCommandBuffer.waitUntilCompleted()
+    }
 }

Memola/Features/Memo/PenTool/PenToolView.swift

@@ -129,6 +129,7 @@ struct PenToolView: View {
                 .font(.title2)
                 .contentShape(.circle)
         }
+        .foregroundStyle(.green)
         .hoverEffect(.lift)
         .padding(10)
     }