feat: generate quad texture programmatically

Memola/Canvas/Core/PipelineStates.swift

@@ -77,7 +77,7 @@ struct PipelineStates {
         let library = renderer.library
         let pipelineDescriptor = MTLRenderPipelineDescriptor()
         pipelineDescriptor.vertexFunction = library.makeFunction(name: "vertex_stroke")
-        pipelineDescriptor.fragmentFunction = library.makeFunction(name: "fragment_stroke")
+        pipelineDescriptor.fragmentFunction = library.makeFunction(name: "fragment_stroke_eraser")
         pipelineDescriptor.colorAttachments[0].pixelFormat = pixelFormat ?? renderer.pixelFormat
         pipelineDescriptor.label = "Eraser Pipeline State"
 

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

@@ -83,13 +83,17 @@ extension Stroke {
 extension Stroke {
     func prepare(device: MTLDevice) {
         guard texture == nil else { return }
-        texture = penStyle.loadTexture(on: device)
+        if penStyle.textureName != nil {
+            texture = penStyle.loadTexture(on: device)
+        }
     }
 
     func draw(device: MTLDevice, renderEncoder: MTLRenderCommandEncoder) {
         guard !isEmpty, let indexBuffer else { return }
         prepare(device: device)
-        renderEncoder.setFragmentTexture(texture, index: 0)
+        if penStyle.textureName != nil {
+            renderEncoder.setFragmentTexture(texture, index: 0)
+        }
         renderEncoder.setVertexBuffer(vertexBuffer, offset: 0, index: 0)
         renderEncoder.drawIndexedPrimitives(
             type: .triangle,

Memola/Canvas/RenderPasses/PhotoBackgroundRenderPass.swift

@@ -52,5 +52,6 @@ class PhotoBackgroundRenderPass: RenderPass {
 
         renderEncoder.endEncoding()
         commandBuffer.commit()
+        commandBuffer.waitUntilCompleted()
     }
 }

Memola/Canvas/RenderPasses/PhotoRenderPass.swift

@@ -41,5 +41,6 @@ class PhotoRenderPass: RenderPass {
 
         renderEncoder.endEncoding()
         commandBuffer.commit()
+        commandBuffer.waitUntilCompleted()
     }
 }

Memola/Canvas/RenderPasses/ViewPortRenderPass.swift

@@ -54,7 +54,7 @@ class ViewPortRenderPass: RenderPass {
             renderEncoder.setRenderPipelineState(viewPortUpdatePipelineState)
 
             renderEncoder.setFragmentTexture(photoBackgroundTexture, index: 0)
-            canvas.renderViewPort(device: renderer.device, renderEncoder: renderEncoder)
+            canvas.renderViewPortUpdate(device: renderer.device, renderEncoder: renderEncoder)
 
             renderEncoder.setFragmentTexture(cacheTexture, index: 0)
             canvas.renderViewPortUpdate(device: renderer.device, renderEncoder: renderEncoder)

Memola/Canvas/Shaders/Stroke.metal

@@ -53,3 +53,21 @@ fragment float4 fragment_stroke(
     float4 color = float4(texture.sample(textureSampler, out.textCoord));
     return float4(1, 1, 1, color.a);
 }
+
+fragment float4 fragment_stroke_eraser(
+    VertexOut out [[stage_in]],
+    texture2d<float> texture [[texture(0)]]
+) {
+    float2 circleCenter = float2(0.5, 0.5);
+    float radius = 0.4;
+    float4 circleColor = float4(1.0, 0.0, 0.0, 1.0);
+
+    float2 fragCoord = out.textCoord;
+    float distance = length(fragCoord - circleCenter);
+
+    if (distance < radius) {
+        return circleColor;
+    } else {
+        return float4(0.0);
+    }
+}

Memola/Canvas/Tool/Pen/Core/PenStyle.swift

@@ -10,7 +10,7 @@ import Foundation
 
 protocol PenStyle {
     var icon: (base: String, tip: String?) { get }
-    var textureName: String { get }
+    var textureName: String? { get }
     var thickness: (min: CGFloat, max: CGFloat) { get }
     var thicknessSteps: [CGFloat] { get }
     var color: [CGFloat] { get }
@@ -22,6 +22,7 @@ protocol PenStyle {
 extension PenStyle {
     @discardableResult
     func loadTexture(on device: MTLDevice) -> MTLTexture? {
-        Textures.createPenTexture(with: textureName, on: device)
+        guard let textureName else { return nil }
+        return Textures.createPenTexture(with: textureName, on: device)
     }
 }

Memola/Canvas/Tool/Pen/PenStyles/EraserPenStyle.swift

@@ -10,7 +10,7 @@ import Foundation
 struct EraserPenStyle: PenStyle {
     var icon: (base: String, tip: String?) = ("eraser", nil)
 
-    var textureName: String = "point-texture"
+    var textureName: String? = nil
 
     var thickness: (min: CGFloat, max: CGFloat) = (0.5, 30)
 

Memola/Canvas/Tool/Pen/PenStyles/MarkerPenStyle.swift

@@ -10,7 +10,7 @@ import Foundation
 struct MarkerPenStyle: PenStyle {
     var icon: (base: String, tip: String?) = ("marker-base", "marker-tip")
 
-    var textureName: String = "point-texture"
+    var textureName: String? = "point-texture"
 
     var thickness: (min: CGFloat, max: CGFloat) = (0.5, 30)