chore: refactor render pipeline

Memola.xcodeproj/project.pbxproj

@@ -22,6 +22,7 @@
 		EC35655A2BF060D900A4E0BF /* Quad.metal in Sources */ = {isa = PBXBuildFile; fileRef = EC3565592BF060D900A4E0BF /* Quad.metal */; };
 		EC35655C2BF0712A00A4E0BF /* Float++.swift in Sources */ = {isa = PBXBuildFile; fileRef = EC35655B2BF0712A00A4E0BF /* Float++.swift */; };
 		EC37FB122C1B2DD90008D976 /* ToolSelection.swift in Sources */ = {isa = PBXBuildFile; fileRef = EC37FB112C1B2DD90008D976 /* ToolSelection.swift */; };
+		EC42F7852C25267000E86E96 /* ElementGroup.swift in Sources */ = {isa = PBXBuildFile; fileRef = EC42F7842C25267000E86E96 /* ElementGroup.swift */; };
 		EC4538892BEBCAE000A86FEC /* Quad.swift in Sources */ = {isa = PBXBuildFile; fileRef = EC4538882BEBCAE000A86FEC /* Quad.swift */; };
 		EC5050072BF65CED00B4D86E /* PenDropDelegate.swift in Sources */ = {isa = PBXBuildFile; fileRef = EC5050062BF65CED00B4D86E /* PenDropDelegate.swift */; };
 		EC50500D2BF6674400B4D86E /* OnDragViewModifier.swift in Sources */ = {isa = PBXBuildFile; fileRef = EC50500C2BF6674400B4D86E /* OnDragViewModifier.swift */; };
@@ -124,6 +125,7 @@
 		EC3565592BF060D900A4E0BF /* Quad.metal */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.metal; path = Quad.metal; sourceTree = "<group>"; };
 		EC35655B2BF0712A00A4E0BF /* Float++.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = "Float++.swift"; sourceTree = "<group>"; };
 		EC37FB112C1B2DD90008D976 /* ToolSelection.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = ToolSelection.swift; sourceTree = "<group>"; };
+		EC42F7842C25267000E86E96 /* ElementGroup.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = ElementGroup.swift; sourceTree = "<group>"; };
 		EC4538882BEBCAE000A86FEC /* Quad.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = Quad.swift; sourceTree = "<group>"; };
 		EC5050062BF65CED00B4D86E /* PenDropDelegate.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = PenDropDelegate.swift; sourceTree = "<group>"; };
 		EC50500C2BF6674400B4D86E /* OnDragViewModifier.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = OnDragViewModifier.swift; sourceTree = "<group>"; };
@@ -713,6 +715,7 @@
 			isa = PBXGroup;
 			children = (
 				ECD12A892C19EFB000B96E12 /* Element.swift */,
+				EC42F7842C25267000E86E96 /* ElementGroup.swift */,
 			);
 			path = Core;
 			sourceTree = "<group>";
@@ -906,6 +909,7 @@
 				ECA738F42BE612A000A4542E /* Array++.swift in Sources */,
 				EC4538892BEBCAE000A86FEC /* Quad.swift in Sources */,
 				ECE883BD2C00AA170045C53D /* EraserStroke.swift in Sources */,
+				EC42F7852C25267000E86E96 /* ElementGroup.swift in Sources */,
 				ECD12A8F2C1AEBA400B96E12 /* Photo.swift in Sources */,
 				ECD12A932C1B062000B96E12 /* Photo.metal in Sources */,
 				ECA7388F2BE600DA00A4542E /* Grid.metal in Sources */,

Memola/Canvas/Abstracts/RenderPass.swift

@@ -12,5 +12,5 @@ protocol RenderPass {
     var label: String { get }
     var descriptor: MTLRenderPassDescriptor? { get set }
     func resize(on view: MTKView, to size: CGSize, with renderer: Renderer)
-    func draw(on canvas: Canvas, with renderer: Renderer)
+    func draw(into commandBuffer: MTLCommandBuffer, on canvas: Canvas, with renderer: Renderer)
 }

Memola/Canvas/Core/Renderer.swift

@@ -72,13 +72,17 @@ final class Renderer {
     }
 
     func draw(in view: MTKView, on canvas: Canvas) {
+        guard let commandBuffer = commandQueue.makeCommandBuffer() else {
+            NSLog("[Memola] - Unable to create command buffer")
+            return
+        }
         if !updatesViewPort {
             strokeRenderPass.eraserRenderPass = eraserRenderPass
             graphicRenderPass.photoRenderPass = photoRenderPass
             graphicRenderPass.strokeRenderPass = strokeRenderPass
             graphicRenderPass.eraserRenderPass = eraserRenderPass
             graphicRenderPass.photoBackgroundRenderPass = photoBackgroundRenderPass
-            graphicRenderPass.draw(on: canvas, with: self)
+            graphicRenderPass.draw(into: commandBuffer, on: canvas, with: self)
         }
 
         cacheRenderPass.clearsTexture = graphicRenderPass.clearsTexture
@@ -87,11 +91,11 @@ final class Renderer {
         cacheRenderPass.eraserRenderPass = eraserRenderPass
         cacheRenderPass.graphicTexture = graphicRenderPass.graphicTexture
         cacheRenderPass.graphicPipelineState = graphicRenderPass.graphicPipelineState
-        cacheRenderPass.draw(on: canvas, with: self)
+        cacheRenderPass.draw(into: commandBuffer, on: canvas, with: self)
 
         viewPortRenderPass.descriptor = view.currentRenderPassDescriptor
         viewPortRenderPass.photoBackgroundTexture = photoBackgroundRenderPass.photoBackgroundTexture
         viewPortRenderPass.cacheTexture = cacheRenderPass.cacheTexture
-        viewPortRenderPass.draw(on: canvas, with: self)
+        viewPortRenderPass.draw(into: commandBuffer, on: canvas, with: self)
     }
 }

Memola/Canvas/Elements/Core/Element.swift

@@ -41,6 +41,18 @@ enum Element: Equatable, Comparable {
         }
     }
 
+    var elementGroupType: ElementGroup.ElementGroupType {
+        switch self {
+        case .stroke(let anyStroke):
+            switch anyStroke.value.style {
+            case .marker: return .stroke
+            case .eraser: return .eraser
+            }
+        case .photo:
+            return .photo
+        }
+    }
+
     static func < (lhs: Element, rhs: Element) -> Bool {
         switch (lhs, rhs) {
         case let (.stroke(leftStroke), .stroke(rightStroke)):
@@ -53,4 +65,15 @@ enum Element: Equatable, Comparable {
             stroke.value.createdAt < photo.createdAt
         }
     }
+
+    static func ^= (lhs: Element, rhs: Element) -> Bool {
+        switch (lhs, rhs) {
+        case let (.stroke(leftStroke), .stroke(rightStroke)):
+            leftStroke ^= rightStroke
+        case let (.photo(leftPhoto), .photo(rightPhoto)):
+            leftPhoto == rightPhoto
+        default:
+            false
+        }
+    }
 }

Memola/Canvas/Elements/Core/ElementGroup.swift

@@ -0,0 +1,51 @@
+//
+//  ElementGroup.swift
+//  Memola
+//
+//  Created by Dscyre Scotti on 6/21/24.
+//
+
+import Foundation
+
+class ElementGroup {
+    var elements: [Element] = []
+    var type: ElementGroupType
+
+    init(_ element: Element) {
+        elements = [element]
+        type = element.elementGroupType
+    }
+
+    var isEmpty: Bool { elements.isEmpty }
+
+    func add(_ element: Element) {
+        elements.append(element)
+    }
+
+    func isSameElement(_ element: Element) -> Bool {
+        guard let last = elements.last else { return false }
+        return element ^= last
+    }
+
+    func getPenStyle() -> PenStyle? {
+        if let last = elements.last, case let .stroke(anyStroke) = last {
+            return anyStroke.value.penStyle
+        }
+        return nil
+    }
+
+    func getPenColor() -> [CGFloat]? {
+        if let last = elements.last, case let .stroke(anyStroke) = last {
+            return anyStroke.value.color
+        }
+        return nil
+    }
+}
+
+extension ElementGroup {
+    enum ElementGroupType {
+        case stroke
+        case eraser
+        case photo
+    }
+}

Memola/Canvas/Elements/Geometries/Stroke/Core/AnyStroke.swift

@@ -18,6 +18,10 @@ struct AnyStroke: Equatable, Comparable {
         lhs.value.id == rhs.value.id
     }
 
+    static func ^= (lhs: AnyStroke, rhs: AnyStroke) -> Bool {
+        lhs.value.color == rhs.value.color && lhs.value.style == rhs.value.style
+    }
+
     static func < (lhs: AnyStroke, rhs: AnyStroke) -> Bool {
         lhs.value.createdAt < rhs.value.createdAt
     }

Memola/Canvas/Elements/Geometries/Stroke/Core/Stroke.swift

@@ -8,7 +8,7 @@
 import MetalKit
 import Foundation
 
-protocol Stroke: AnyObject, Drawable, Hashable, Equatable, Comparable {
+protocol Stroke: AnyObject, Drawable, Hashable, Equatable {
     var id: UUID { get set }
     var bounds: [CGFloat] { get set }
     var color: [CGFloat] { get set }
@@ -102,8 +102,6 @@ extension Stroke {
             indexBuffer: indexBuffer,
             indexBufferOffset: 0
         )
-        self.vertexBuffer = nil
-        self.indexBuffer = nil
     }
 }
 

Memola/Canvas/Elements/Geometries/Stroke/Strokes/PenStroke.swift

@@ -167,7 +167,5 @@ final class PenStroke: Stroke, @unchecked Sendable {
             indexBuffer: erasedIndexBuffer,
             indexBufferOffset: 0
         )
-        self.erasedIndexBuffer = nil
-        self.erasedVertexBuffer = nil
     }
 }

Memola/Canvas/Elements/Photo/Photo.swift

@@ -8,7 +8,7 @@
 import MetalKit
 import Foundation
 
-final class Photo: @unchecked Sendable, Equatable, Comparable {
+final class Photo: @unchecked Sendable, Equatable {
     var id: UUID = UUID()
     var size: CGSize
     var origin: CGPoint
@@ -93,6 +93,10 @@ extension Photo {
     static func < (lhs: Photo, rhs: Photo) -> Bool {
         lhs.createdAt < rhs.createdAt
     }
+
+    static func ^= (lhs: Photo, rhs: Photo) -> Bool {
+        lhs == rhs
+    }
 }
 
 extension Photo {

Memola/Canvas/RenderPasses/CacheRenderPass.swift

@@ -34,53 +34,16 @@ class CacheRenderPass: RenderPass {
         cacheTexture = Textures.createCacheTexture(from: renderer, size: size, pixelFormat: view.colorPixelFormat)
     }
 
-    func draw(on canvas: Canvas, with renderer: Renderer) {
+    func draw(into commandBuffer: any MTLCommandBuffer, on canvas: Canvas, with renderer: Renderer) {
-        guard let descriptor, let strokeRenderPass, let eraserRenderPass, let photoRenderPass else { return }
+        guard let descriptor else { return }
 
-        copyTexture(on: canvas, with: renderer)
+        // MARK: - Copying texture
-
-        guard let graphicPipelineState else { return }
-        descriptor.colorAttachments[0].texture = cacheTexture
-        descriptor.colorAttachments[0].clearColor = MTLClearColor(red: 1, green: 1, blue: 1, alpha: 0)
-        descriptor.colorAttachments[0].loadAction = clearsTexture ? .clear : .load
-        descriptor.colorAttachments[0].storeAction = .store
-
-        let graphicContext = canvas.graphicContext
-        if let element = graphicContext.currentElement {
-            switch element {
-            case .stroke(let anyStroke):
-                let stroke = anyStroke.value
-                switch stroke.style {
-                case .eraser:
-                    eraserRenderPass.stroke = stroke
-                    eraserRenderPass.descriptor = descriptor
-                    eraserRenderPass.draw(on: canvas, with: renderer)
-                case .marker:
-                    canvas.setGraphicRenderType(.inProgress)
-                    strokeRenderPass.stroke = stroke
-                    strokeRenderPass.graphicDescriptor = descriptor
-                    strokeRenderPass.graphicPipelineState = graphicPipelineState
-                    strokeRenderPass.draw(on: canvas, with: renderer)
-                }
-            case .photo(let photo):
-                photoRenderPass.photo = photo
-                photoRenderPass.descriptor = descriptor
-                photoRenderPass.draw(on: canvas, with: renderer)
-            }
-            clearsTexture = false
-        }
-    }
-
-    private func copyTexture(on canvas: Canvas, with renderer: Renderer) {
         guard let graphicTexture, let cacheTexture else { return }
         guard let cachePipelineState else { return }
-        guard let copyCommandBuffer = renderer.commandQueue.makeCommandBuffer() else {
+        guard let computeEncoder = commandBuffer.makeComputeCommandEncoder() else {
             return
         }
-        guard let computeEncoder = copyCommandBuffer.makeComputeCommandEncoder() else {
+        computeEncoder.label = "Cache Compute Encoder"
-            return
-        }
-        computeEncoder.label = label
 
         computeEncoder.setComputePipelineState(cachePipelineState)
         computeEncoder.setTexture(graphicTexture, index: 0)
@@ -93,6 +56,34 @@ class CacheRenderPass: RenderPass {
         )
         computeEncoder.dispatchThreadgroups(threadgroupCount, threadsPerThreadgroup: threadgroupSize)
         computeEncoder.endEncoding()
-        copyCommandBuffer.commit()
+
+        // MARK: - Drawing 
+        guard let graphicPipelineState else { return }
+        descriptor.colorAttachments[0].texture = cacheTexture
+        descriptor.colorAttachments[0].clearColor = MTLClearColor(red: 1, green: 1, blue: 1, alpha: 0)
+        descriptor.colorAttachments[0].loadAction = clearsTexture ? .clear : .load
+        descriptor.colorAttachments[0].storeAction = .store
+
+        let graphicContext = canvas.graphicContext
+        if let element = graphicContext.currentElement {
+            let elementGroup = ElementGroup(element)
+            switch elementGroup.type {
+            case .stroke:
+                canvas.setGraphicRenderType(.inProgress)
+                strokeRenderPass?.elementGroup = elementGroup
+                strokeRenderPass?.graphicDescriptor = descriptor
+                strokeRenderPass?.graphicPipelineState = graphicPipelineState
+                strokeRenderPass?.draw(into: commandBuffer, on: canvas, with: renderer)
+            case .eraser:
+                eraserRenderPass?.elementGroup = elementGroup
+                eraserRenderPass?.descriptor = descriptor
+                eraserRenderPass?.draw(into: commandBuffer, on: canvas, with: renderer)
+            case .photo:
+                photoRenderPass?.elementGroup = elementGroup
+                photoRenderPass?.descriptor = descriptor
+                photoRenderPass?.draw(into: commandBuffer, on: canvas, with: renderer)
+            }
+            clearsTexture = false
+        }
     }
 }

Memola/Canvas/RenderPasses/EraserRenderPass.swift

@@ -16,7 +16,7 @@ class EraserRenderPass: RenderPass {
     var eraserPipelineState: MTLRenderPipelineState?
     var quadPipelineState: MTLComputePipelineState?
 
-    var stroke: (any Stroke)?
+    var elementGroup: ElementGroup?
     weak var graphicTexture: MTLTexture?
 
     init(renderer: Renderer) {
@@ -26,49 +26,24 @@ class EraserRenderPass: RenderPass {
 
     func resize(on view: MTKView, to size: CGSize, with renderer: Renderer) { }
 
-    func draw(on canvas: Canvas, with renderer: Renderer) {
+    func draw(into commandBuffer: any MTLCommandBuffer, on canvas: Canvas, with renderer: Renderer) {
+        guard let elementGroup else { return }
         guard let descriptor else { return }
 
-        generateVertexBuffer(on: canvas, with: renderer)
+        // MARK: - Generating vertices
-
+        guard !elementGroup.isEmpty, let quadPipelineState else { return }
-        guard let commandBuffer = renderer.commandQueue.makeCommandBuffer() else { return }
+        let eraserStrokes = elementGroup.elements.compactMap { element -> EraserStroke? in
-        commandBuffer.label = "Eraser Command Buffer"
+            guard case .stroke(let anyStroke) = element else { return nil }
-
+            return anyStroke.value as? EraserStroke
-        guard let renderEncoder = commandBuffer.makeRenderCommandEncoder(descriptor: descriptor) else { return }
-        renderEncoder.label = label
-
-        guard let eraserPipelineState else { return }
-        renderEncoder.setRenderPipelineState(eraserPipelineState)
-
-        canvas.setUniformsBuffer(device: renderer.device, renderEncoder: renderEncoder)
-        if let stroke = stroke as? PenStroke {
-            stroke.erase(device: renderer.device, renderEncoder: renderEncoder)
-        } else {
-            stroke?.draw(device: renderer.device, renderEncoder: renderEncoder)
         }
+        let quads = eraserStrokes.flatMap { $0.quads }
+        guard !quads.isEmpty else { return }
+        guard let computeEncoder = commandBuffer.makeComputeCommandEncoder() else { return }
 
-        renderEncoder.endEncoding()
+        computeEncoder.label = "Quad Compute Encoder"
-        commandBuffer.commit()
-    }
 
-    private func generateVertexBuffer(on canvas: Canvas, with renderer: Renderer) {
+        let quadCount = quads.endIndex
-        guard let stroke else { return }
+        let quadBuffer = renderer.device.makeBuffer(bytes: quads, length: MemoryLayout<Quad>.stride * quadCount, options: [])
-        let quadCount: Int
-        var quads: [Quad]
-        if let stroke = stroke as? PenStroke {
-            quads = stroke.getAllErasedQuads()
-            quadCount = quads.endIndex
-        } else {
-            quadCount = stroke.quads.endIndex
-            quads = stroke.quads
-        }
-        guard !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 quadBuffer = renderer.device.makeBuffer(bytes: &quads, length: MemoryLayout<Quad>.stride * quadCount, options: [])
         let indexBuffer = renderer.device.makeBuffer(length: MemoryLayout<UInt>.stride * quadCount * 6, options: [.cpuCacheModeWriteCombined])
         let vertexBuffer = renderer.device.makeBuffer(length: MemoryLayout<QuadVertex>.stride * quadCount * 4, options: [.cpuCacheModeWriteCombined])
 
@@ -77,20 +52,30 @@ class EraserRenderPass: RenderPass {
         computeEncoder.setBuffer(indexBuffer, offset: 0, index: 1)
         computeEncoder.setBuffer(vertexBuffer, offset: 0, index: 2)
 
-        if let stroke = stroke as? PenStroke {
-            stroke.erasedIndexBuffer = indexBuffer
-            stroke.erasedVertexBuffer = vertexBuffer
-            stroke.erasedQuadCount = quadCount
-        } else {
-            stroke.indexBuffer = indexBuffer
-            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()
+        // MARK: - Rendering eraser
+        guard let renderEncoder = commandBuffer.makeRenderCommandEncoder(descriptor: descriptor) else { return }
+        renderEncoder.label = "Stroke Render Encoder"
+
+        guard let eraserPipelineState else { return }
+        renderEncoder.setRenderPipelineState(eraserPipelineState)
+
+        canvas.setUniformsBuffer(device: renderer.device, renderEncoder: renderEncoder)
+
+        if let indexBuffer {
+            renderEncoder.setVertexBuffer(vertexBuffer, offset: 0, index: 0)
+            renderEncoder.drawIndexedPrimitives(
+                type: .triangle,
+                indexCount: quads.endIndex * 6,
+                indexType: .uint32,
+                indexBuffer: indexBuffer,
+                indexBufferOffset: 0
+            )
+        }
+        renderEncoder.endEncoding()
     }
 }

Memola/Canvas/RenderPasses/GraphicRenderPass.swift

@@ -33,94 +33,71 @@ class GraphicRenderPass: RenderPass {
         clearsTexture = true
     }
 
-    func draw(on canvas: Canvas, with renderer: Renderer) {
+    func draw(into commandBuffer: any MTLCommandBuffer, on canvas: Canvas, with renderer: Renderer) {
-        guard let strokeRenderPass, let eraserRenderPass, let photoRenderPass, let photoBackgroundRenderPass else { return }
+        descriptor?.colorAttachments[0].texture = graphicTexture
-        guard let descriptor else { return }
+        descriptor?.colorAttachments[0].clearColor = MTLClearColor(red: 1, green: 1, blue: 1, alpha: 0)
-
+        descriptor?.colorAttachments[0].storeAction = .store
-        guard let graphicPipelineState else { return }
-        guard let graphicTexture else { return }
-
-        descriptor.colorAttachments[0].texture = graphicTexture
-        descriptor.colorAttachments[0].clearColor = MTLClearColor(red: 1, green: 1, blue: 1, alpha: 0)
-        descriptor.colorAttachments[0].storeAction = .store
 
         let graphicContext = canvas.graphicContext
         if renderer.redrawsGraphicRender {
             canvas.setGraphicRenderType(.finished)
+            var elementGroup: ElementGroup?
+            let start = Date.now.timeIntervalSince1970 * 1000
             for _element in graphicContext.tree.search(box: canvas.bounds.box) {
                 if graphicContext.previousElement == _element || graphicContext.currentElement == _element {
                     continue
                 }
-                switch _element {
+                if elementGroup == nil {
-                case .stroke(let _stroke):
+                    let _elementGroup = ElementGroup(_element)
-                    let stroke = _stroke.value
+                    elementGroup = _elementGroup
-                    guard stroke.isVisible(in: canvas.bounds) else { continue }
+                } else {
-                    descriptor.colorAttachments[0].loadAction = clearsTexture ? .clear : .load
+                    guard let _elementGroup = elementGroup else { return }
-                    switch stroke.style {
+                    if _elementGroup.isSameElement(_element) {
-                    case .eraser:
+                        _elementGroup.add(_element)
-                        eraserRenderPass.stroke = stroke
+                    } else {
-                        eraserRenderPass.descriptor = descriptor
+                        if let elementGroup {
-                        eraserRenderPass.draw(on: canvas, with: renderer)
+                            draw(for: elementGroup, into: commandBuffer, on: canvas, with: renderer)
-                    case .marker:
+                        }
-                        canvas.setGraphicRenderType(.finished)
+                        let _elementGroup = ElementGroup(_element)
-                        strokeRenderPass.stroke = stroke
+                        elementGroup = _elementGroup
-                        strokeRenderPass.graphicDescriptor = descriptor
-                        strokeRenderPass.graphicPipelineState = graphicPipelineState
-                        strokeRenderPass.draw(on: canvas, with: renderer)
                     }
-                    clearsTexture = false
-                case .photo(let photo):
-                    descriptor.colorAttachments[0].loadAction = clearsTexture ? .clear : .load
-                    photoRenderPass.photo = photo
-                    photoRenderPass.descriptor = descriptor
-                    photoRenderPass.draw(on: canvas, with: renderer)
-
-                    photoBackgroundRenderPass.photo = photo
-                    photoBackgroundRenderPass.clearsTexture = clearsTexture
-                    photoBackgroundRenderPass.draw(on: canvas, with: renderer)
-
-                    clearsTexture = false
                 }
             }
+            if let elementGroup {
+                draw(for: elementGroup, into: commandBuffer, on: canvas, with: renderer)
+            }
+            let end = Date.now.timeIntervalSince1970 * 1000
+            NSLog("[Memola] - duration: \(end - start)")
             renderer.redrawsGraphicRender = false
         }
-
         if let element = graphicContext.previousElement {
-            descriptor.colorAttachments[0].loadAction = clearsTexture ? .clear : .load
+            let elementGroup = ElementGroup(element)
-            switch element {
+            draw(for: elementGroup, into: commandBuffer, on: canvas, with: renderer)
-            case .stroke(let anyStroke):
-                let stroke = anyStroke.value
-                switch stroke.style {
-                case .eraser:
-                    eraserRenderPass.stroke = stroke
-                    eraserRenderPass.descriptor = descriptor
-                    eraserRenderPass.draw(on: canvas, with: renderer)
-                case .marker:
-                    canvas.setGraphicRenderType(.newlyFinished)
-                    strokeRenderPass.stroke = stroke
-                    strokeRenderPass.graphicDescriptor = descriptor
-                    strokeRenderPass.graphicPipelineState = graphicPipelineState
-                    strokeRenderPass.draw(on: canvas, with: renderer)
-                }
-            case .photo(let photo):
-                photoRenderPass.photo = photo
-                photoRenderPass.descriptor = descriptor
-                photoRenderPass.draw(on: canvas, with: renderer)
-
-                photoBackgroundRenderPass.photo = photo
-                photoBackgroundRenderPass.clearsTexture = clearsTexture
-                photoBackgroundRenderPass.draw(on: canvas, with: renderer)
-            }
-            clearsTexture = false
             graphicContext.previousElement = nil
         }
+    }
 
-        let eraserStrokes = graphicContext.eraserStrokes
+    private func draw(for elementGroup: ElementGroup, into commandBuffer: MTLCommandBuffer, on canvas: Canvas, with renderer: Renderer) {
-        for eraserStroke in eraserStrokes {
+        switch elementGroup.type {
-            if eraserStroke.finishesSaving {
+        case .stroke:
-                graphicContext.eraserStrokes.remove(eraserStroke)
+            descriptor?.colorAttachments[0].loadAction = clearsTexture ? .clear : .load
-                continue
+            strokeRenderPass?.elementGroup = elementGroup
-            }
+            strokeRenderPass?.graphicDescriptor = descriptor
+            strokeRenderPass?.graphicPipelineState = graphicPipelineState
+            strokeRenderPass?.draw(into: commandBuffer, on: canvas, with: renderer)
+            clearsTexture = false
+        case .eraser:
+            descriptor?.colorAttachments[0].loadAction = clearsTexture ? .clear : .load
+            eraserRenderPass?.elementGroup = elementGroup
+            eraserRenderPass?.descriptor = descriptor
+            eraserRenderPass?.draw(into: commandBuffer, on: canvas, with: renderer)
+            clearsTexture = false
+        case .photo:
+            descriptor?.colorAttachments[0].loadAction = clearsTexture ? .clear : .load
+            photoRenderPass?.elementGroup = elementGroup
+            photoRenderPass?.descriptor = descriptor
+            photoRenderPass?.draw(into: commandBuffer, on: canvas, with: renderer)
+            clearsTexture = false
         }
     }
 }

Memola/Canvas/RenderPasses/PhotoBackgroundRenderPass.swift

@@ -30,6 +30,10 @@ class PhotoBackgroundRenderPass: RenderPass {
         photoBackgroundTexture = Textures.createPhotoBackgroundTexture(from: renderer, size: size, pixelFormat: renderer.pixelFormat)
     }
 
+    func draw(into commandBuffer: any MTLCommandBuffer, on canvas: Canvas, with renderer: Renderer) {
+        
+    }
+
     func draw(on canvas: Canvas, with renderer: Renderer) {
         guard let descriptor else { return }
 

Memola/Canvas/RenderPasses/PhotoRenderPass.swift

@@ -16,7 +16,7 @@ class PhotoRenderPass: RenderPass {
     var photoPipelineState: MTLRenderPipelineState?
     weak var graphicTexture: MTLTexture?
 
-    var photo: Photo?
+    var elementGroup: ElementGroup?
 
     init(renderer: Renderer) {
         photoPipelineState = PipelineStates.createPhotoPipelineState(from: renderer)
@@ -24,11 +24,16 @@ class PhotoRenderPass: RenderPass {
 
     func resize(on view: MTKView, to size: CGSize, with renderer: Renderer) { }
 
-    func draw(on canvas: Canvas, with renderer: Renderer) {
+    func draw(into commandBuffer: any MTLCommandBuffer, on canvas: Canvas, with renderer: Renderer) {
+        guard let elementGroup else { return }
         guard let descriptor else { return }
 
-        guard let commandBuffer = renderer.commandQueue.makeCommandBuffer() else { return }
+        guard !elementGroup.isEmpty else { return }
-        commandBuffer.label = "Photo Command Buffer"
+
+        let photos = elementGroup.elements.compactMap { element -> Photo? in
+            guard case .photo(let photo) = element else { return nil }
+            return photo
+        }
 
         guard let renderEncoder = commandBuffer.makeRenderCommandEncoder(descriptor: descriptor) else { return }
         renderEncoder.label = label
@@ -37,10 +42,11 @@ class PhotoRenderPass: RenderPass {
         renderEncoder.setRenderPipelineState(photoPipelineState)
 
         canvas.setUniformsBuffer(device: renderer.device, renderEncoder: renderEncoder)
-        photo?.draw(device: renderer.device, renderEncoder: renderEncoder)
+
+        for photo in photos {
+            photo.draw(device: renderer.device, renderEncoder: renderEncoder)
+        }
 
         renderEncoder.endEncoding()
-        commandBuffer.commit()
-        commandBuffer.waitUntilCompleted()
     }
 }

Memola/Canvas/RenderPasses/StrokeRenderPass.swift

@@ -18,7 +18,7 @@ class StrokeRenderPass: RenderPass {
     var quadPipelineState: MTLComputePipelineState?
     weak var graphicPipelineState: MTLRenderPipelineState?
 
-    var stroke: (any Stroke)?
+    var elementGroup: ElementGroup?
     var strokeTexture: MTLTexture?
 
     weak var eraserRenderPass: EraserRenderPass?
@@ -34,51 +34,26 @@ class StrokeRenderPass: RenderPass {
         strokeTexture = Textures.createStrokeTexture(from: renderer, size: size, pixelFormat: view.colorPixelFormat)
     }
     
-    func draw(on canvas: Canvas, with renderer: Renderer) {
+    func draw(into commandBuffer: any MTLCommandBuffer, on canvas: Canvas, with renderer: Renderer) {
+        guard let elementGroup else { return }
         guard let descriptor else { return }
 
-        generateVertexBuffer(on: canvas, with: renderer)
+        // MARK: - Generating vertices
-
+        guard !elementGroup.isEmpty, let quadPipelineState else { return }
-        guard let strokeTexture else { return }
+        let penStrokes = elementGroup.elements.compactMap { element -> PenStroke? in
-        descriptor.colorAttachments[0].texture = strokeTexture
+            guard case .stroke(let anyStroke) = element else { return nil }
-        descriptor.colorAttachments[0].clearColor = MTLClearColor(red: 1, green: 1, blue: 1, alpha: 0)
+            return anyStroke.value as? PenStroke
-        descriptor.colorAttachments[0].loadAction = .clear
-        descriptor.colorAttachments[0].storeAction = .store
-
-        guard let commandBuffer = renderer.commandQueue.makeCommandBuffer() else { return }
-        commandBuffer.label = "Stroke Command Buffer"
-
-        guard let renderEncoder = commandBuffer.makeRenderCommandEncoder(descriptor: descriptor) else { return }
-        renderEncoder.label = label
-
-        guard let strokePipelineState else { return }
-        renderEncoder.setRenderPipelineState(strokePipelineState)
-
-        canvas.setUniformsBuffer(device: renderer.device, renderEncoder: renderEncoder)
-        stroke?.draw(device: renderer.device, renderEncoder: renderEncoder)
-        renderEncoder.endEncoding()
-        commandBuffer.commit()
-
-        if let eraserRenderPass, let stroke = stroke as? PenStroke, !stroke.isEmptyErasedQuads {
-            descriptor.colorAttachments[0].loadAction = .load
-            eraserRenderPass.stroke = stroke
-            eraserRenderPass.descriptor = descriptor
-            eraserRenderPass.draw(on: canvas, with: renderer)
         }
+        let penStroke = penStrokes.first
+        let quads = penStrokes.flatMap { $0.quads }
+        let erasedQuads = Set(penStrokes.flatMap { $0.eraserStrokes }).flatMap { $0.quads }
+        guard !quads.isEmpty else { return }
+        guard let computeEncoder = commandBuffer.makeComputeCommandEncoder() else { return }
 
-        drawStrokeTexture(on: canvas, with: renderer)
+        computeEncoder.label = "Quad Compute Encoder"
-    }
 
-    private func generateVertexBuffer(on canvas: Canvas, with renderer: Renderer) {
+        let quadCount = quads.endIndex
-        guard let stroke, !stroke.isEmpty, let quadPipelineState else { return }
+        let quadBuffer = renderer.device.makeBuffer(bytes: quads, length: MemoryLayout<Quad>.stride * quadCount, options: [])
-        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 indexBuffer = renderer.device.makeBuffer(length: MemoryLayout<UInt>.stride * quadCount * 6, options: [.cpuCacheModeWriteCombined])
         let vertexBuffer = renderer.device.makeBuffer(length: MemoryLayout<QuadVertex>.stride * quadCount * 4, options: [.cpuCacheModeWriteCombined])
 
@@ -87,33 +62,94 @@ class StrokeRenderPass: RenderPass {
         computeEncoder.setBuffer(indexBuffer, offset: 0, index: 1)
         computeEncoder.setBuffer(vertexBuffer, offset: 0, index: 2)
 
-        stroke.indexBuffer = indexBuffer
-        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()
-    }
 
-    private func drawStrokeTexture(on canvas: Canvas, with renderer: Renderer) {
+        // MARK: - Rendering stroke
-        guard let stroke else { return }
+        guard let strokeTexture else { return }
+        descriptor.colorAttachments[0].texture = strokeTexture
+        descriptor.colorAttachments[0].clearColor = MTLClearColor(red: 1, green: 1, blue: 1, alpha: 0)
+        descriptor.colorAttachments[0].loadAction = .clear
+        descriptor.colorAttachments[0].storeAction = .store
+
+        guard let renderEncoder = commandBuffer.makeRenderCommandEncoder(descriptor: descriptor) else { return }
+        renderEncoder.label = "Stroke Render Encoder"
+
+        guard let strokePipelineState else { return }
+        renderEncoder.setRenderPipelineState(strokePipelineState)
+
+        canvas.setUniformsBuffer(device: renderer.device, renderEncoder: renderEncoder)
+        
+        if let penStyle = penStroke?.penStyle, let indexBuffer {
+            if penStyle.textureName != nil {
+                let texture = penStyle.loadTexture(on: renderer.device)
+                renderEncoder.setFragmentTexture(texture, index: 0)
+            }
+            renderEncoder.setVertexBuffer(vertexBuffer, offset: 0, index: 0)
+            renderEncoder.drawIndexedPrimitives(
+                type: .triangle,
+                indexCount: quads.endIndex * 6,
+                indexType: .uint32,
+                indexBuffer: indexBuffer,
+                indexBufferOffset: 0
+            )
+        }
+        renderEncoder.endEncoding()
+
+        // MARK: Erasing path
+        if let eraserPipelineState = eraserRenderPass?.eraserPipelineState, !erasedQuads.isEmpty {
+            guard let computeEncoder = commandBuffer.makeComputeCommandEncoder() else { return }
+
+            computeEncoder.label = "Erased Quad Compute Encoder"
+
+            let erasedQuadCount = erasedQuads.endIndex
+            let erasedQuadBuffer = renderer.device.makeBuffer(bytes: erasedQuads, length: MemoryLayout<Quad>.stride * erasedQuadCount, options: [])
+            let erasedIndexBuffer = renderer.device.makeBuffer(length: MemoryLayout<UInt>.stride * erasedQuadCount * 6, options: [.cpuCacheModeWriteCombined])
+            let erasedVertexBuffer = renderer.device.makeBuffer(length: MemoryLayout<QuadVertex>.stride * erasedQuadCount * 4, options: [.cpuCacheModeWriteCombined])
+
+            computeEncoder.setComputePipelineState(quadPipelineState)
+            computeEncoder.setBuffer(erasedQuadBuffer, offset: 0, index: 0)
+            computeEncoder.setBuffer(erasedIndexBuffer, offset: 0, index: 1)
+            computeEncoder.setBuffer(erasedVertexBuffer, offset: 0, index: 2)
+
+            let threadsPerGroup = MTLSize(width: 1, height: 1, depth: 1)
+            let numThreadgroups = MTLSize(width: erasedQuadCount + 1, height: 1, depth: 1)
+            computeEncoder.dispatchThreadgroups(numThreadgroups, threadsPerThreadgroup: threadsPerGroup)
+            computeEncoder.endEncoding()
+
+            descriptor.colorAttachments[0].loadAction = .load
+            guard let renderEncoder = commandBuffer.makeRenderCommandEncoder(descriptor: descriptor) else { return }
+            renderEncoder.label = "Stroke Eraser Render Encoder"
+            
+            renderEncoder.setRenderPipelineState(eraserPipelineState)
+
+            canvas.setUniformsBuffer(device: renderer.device, renderEncoder: renderEncoder)
+            if let erasedIndexBuffer {
+                renderEncoder.setVertexBuffer(erasedVertexBuffer, offset: 0, index: 0)
+                renderEncoder.drawIndexedPrimitives(
+                    type: .triangle,
+                    indexCount: erasedQuadCount * 6,
+                    indexType: .uint32,
+                    indexBuffer: erasedIndexBuffer,
+                    indexBufferOffset: 0
+                )
+            }
+            renderEncoder.endEncoding()
+        }
+
+        // MARK: Drawing on graphic texture
         guard let graphicDescriptor, let graphicPipelineState else { return }
-
-        guard let commandBuffer = renderer.commandQueue.makeCommandBuffer() else { return }
-        commandBuffer.label = "Graphic Command Buffer"
         guard let renderEncoder = commandBuffer.makeRenderCommandEncoder(descriptor: graphicDescriptor) else { return }
-        renderEncoder.label = "Graphic Render Pass"
+        renderEncoder.label = "Stroke Graphic Render Encoder"
         renderEncoder.setRenderPipelineState(graphicPipelineState)
 
         renderEncoder.setFragmentTexture(strokeTexture, index: 0)
-        var uniforms = GraphicUniforms(color: stroke.color)
+        var uniforms = GraphicUniforms(color: elementGroup.getPenColor() ?? [])
         let uniformsBuffer = renderer.device.makeBuffer(bytes: &uniforms, length: MemoryLayout<Uniforms>.size)
         renderEncoder.setVertexBuffer(uniformsBuffer, offset: 0, index: 11)
         canvas.renderGraphic(device: renderer.device, renderEncoder: renderEncoder)
         renderEncoder.endEncoding()
-        commandBuffer.commit()
     }
 }

Memola/Canvas/RenderPasses/ViewPortRenderPass.swift

@@ -29,18 +29,14 @@ class ViewPortRenderPass: RenderPass {
 
     func resize(on view: MTKView, to size: CGSize, with renderer: Renderer) { }
 
-    func draw(on canvas: Canvas, with renderer: Renderer) {
+    func draw(into commandBuffer: any MTLCommandBuffer, on canvas: Canvas, with renderer: Renderer) {
         guard let descriptor else {
             return
         }
-        guard let commandBuffer = renderer.commandQueue.makeCommandBuffer() else {
-            return
-        }
-        commandBuffer.label = "View Port Command Buffer"
         guard let renderEncoder = commandBuffer.makeRenderCommandEncoder(descriptor: descriptor) else {
             return
         }
-        renderEncoder.label = label
+        renderEncoder.label = "View Port Render Encoder"
 
         guard let gridPipelineState else { return }
         renderEncoder.setRenderPipelineState(gridPipelineState)