Allow user to cancel generation.

This will be more useful when we allow multiple images.

Diffusion-macOS/GeneratedImageView.swift

@@ -22,7 +22,15 @@ struct GeneratedImageView: View {
             let step = Int(progress.step) + 1
             let fraction = Double(step) / Double(progress.stepCount)
             let label = "Step \(step) of \(progress.stepCount)"
-            return AnyView(ProgressView(label, value: fraction, total: 1).padding())
+            return AnyView(HStack {
+                ProgressView(label, value: fraction, total: 1).padding()
+                Button {
+                    generation.cancelGeneration()
+                } label: {
+                    Image(systemName: "x.circle.fill").foregroundColor(.gray)
+                }
+                .buttonStyle(.plain)
+            })
         case .complete(_, let image, _, _):
             guard let theImage = image else {
                 return AnyView(Image(systemName: "exclamationmark.triangle").resizable())
@@ -34,6 +42,8 @@ struct GeneratedImageView: View {
             )
         case .failed(_):
             return AnyView(Image(systemName: "exclamationmark.triangle").resizable())
+        case .userCanceled:
+            return AnyView(Text("Generation canceled"))
         }
     }
 }

Diffusion-macOS/StatusView.swift

@@ -20,7 +20,11 @@ struct StatusView: View {
             generation.state = .running(nil)
             do {
                 let result = try await generation.generate()
-                generation.state = .complete(generation.positivePrompt, result.image, result.lastSeed, result.interval)
+                if result.userCanceled {
+                    generation.state = .userCanceled
+                } else {
+                    generation.state = .complete(generation.positivePrompt, result.image, result.lastSeed, result.interval)
+                }
             } catch {
                 generation.state = .failed(error)
             }
@@ -92,6 +96,11 @@ struct StatusView: View {
             }.frame(maxHeight: 25)
         case .failed(let error):
             return errorWithDetails("Generation error", error: error)
+        case .userCanceled:
+            return HStack {
+                Text("Generation canceled.")
+                Spacer()
+            }
         }
     }
     

Diffusion/Pipeline/Pipeline.swift

@@ -18,6 +18,7 @@ struct GenerationResult {
     var image: CGImage?
     var lastSeed: UInt32
     var interval: TimeInterval?
+    var userCanceled: Bool
 }
 
 class Pipeline {
@@ -30,7 +31,8 @@ class Pipeline {
         }
     }
     lazy private(set) var progressPublisher: CurrentValueSubject<StableDiffusionProgress?, Never> = CurrentValueSubject(progress)
-
+    
+    private var canceled = false
 
     init(_ pipeline: StableDiffusionPipeline, maxSeed: UInt32 = UInt32.max) {
         self.pipeline = pipeline
@@ -47,6 +49,7 @@ class Pipeline {
         disableSafety: Bool = false
     ) throws -> GenerationResult {
         let beginDate = Date()
+        canceled = false
         print("Generating...")
         let theSeed = seed ?? UInt32.random(in: 0...maxSeed)
         let images = try pipeline.generateImages(
@@ -60,17 +63,21 @@ class Pipeline {
             scheduler: scheduler
         ) { progress in
             handleProgress(progress)
-            return true
+            return !canceled
         }
         let interval = Date().timeIntervalSince(beginDate)
         print("Got images: \(images) in \(interval)")
         
         // Unwrap the 1 image we asked for, nil means safety checker triggered
         let image = images.compactMap({ $0 }).first
-        return GenerationResult(image: image, lastSeed: theSeed, interval: interval)
+        return GenerationResult(image: image, lastSeed: theSeed, interval: interval, userCanceled: canceled)
     }
 
     func handleProgress(_ progress: StableDiffusionPipeline.Progress) {
         self.progress = progress
     }
+    
+    func setCancelled() {
+        canceled = true
+    }
 }

Diffusion/State.swift

@@ -17,6 +17,7 @@ enum GenerationState {
     case startup
     case running(StableDiffusionProgress?)
     case complete(String, CGImage?, UInt32, TimeInterval?)
+    case userCanceled
     case failed(Error)
 }
 
@@ -63,6 +64,10 @@ class GenerationContext: ObservableObject {
             disableSafety: disableSafety
         )
     }
+    
+    func cancelGeneration() {
+        pipeline?.setCancelled()
+    }
 }
 
 class Settings {