New preferences (#58)

DemoApp/DemoApp/TestViews/ExpandingView.swift

@@ -7,6 +7,7 @@
 
 import Foundation
 import SwiftUI
+import SnapshotPreferences
 
 struct ExpandingView: View {
   var body: some View {

Package.swift

@@ -16,6 +16,12 @@ let package = Package(
         .library(
           name: "SnapshottingTests",
           targets: ["SnapshottingTests"]),
+        // Link the main app to this target to use custom snapshot settings
+        // This lib does not get inserted when running tests to avoid
+        // duplicate symbols.
+        .library(
+          name: "SnapshotPreferences",
+          targets: ["SnapshotPreferences"]),
         // Core functionality for snapshotting exported from the internal package
         .library(
           name: "SnapshotPreviewsCore",
@@ -36,11 +42,12 @@ let package = Package(
         .target(name: "SnapshottingTests"),
         // Core functionality
         .target(name: "SnapshotPreviewsCore"),
+        .target(name: "SnapshotPreferences", dependencies: ["SnapshotPreviewsCore"]),
         // Inserted dylib
         .target(name: "Snapshotting", dependencies: ["SnapshottingSwift"]),
         // Swift code in the inserted dylib
         .target(name: "SnapshottingSwift", dependencies: ["SnapshotPreviewsCore", .product(name: "FlyingFox", package: "FlyingFox")]),
-        .target(name: "PreviewGallery", dependencies: ["SnapshotPreviewsCore"]),
+        .target(name: "PreviewGallery", dependencies: ["SnapshotPreviewsCore", "SnapshotPreferences"]),
         .testTarget(
             name: "SnapshotPreviewsTests",
             dependencies: ["SnapshotPreviewsCore"]),

Sources/SnapshotPreferences/EmergeModifierFinder.swift

@@ -0,0 +1,48 @@
+//
+//  EmergeModifierFinder.swift
+//
+//
+//  Created by Noah Martin on 10/6/23.
+//
+
+import Foundation
+import SwiftUI
+import SnapshotPreviewsCore
+
+// Classes in this file get compiled to an app that use any of the custom preview preferences.
+// The inserted test runner code finds these classes through ObjC runtime functions (NSClassFromString)
+// and Swift reflection (Mirror).
+
+@objc(EmergeModifierState)
+class EmergeModifierState: NSObject {
+
+  @objc
+  static let shared = EmergeModifierState()
+
+  func reset() {
+    expansionPreference = nil
+    renderingMode = nil
+    precision = nil
+  }
+
+  var expansionPreference: Bool?
+  var renderingMode: EmergeRenderingMode.RawValue?
+  var precision: Float?
+}
+
+@objc(EmergeModifierFinder)
+class EmergeModifierFinder: NSObject {
+  let finder: (any View) -> (any View) = { view in
+    EmergeModifierState.shared.reset()
+    return view
+      .onPreferenceChange(ExpansionPreferenceKey.self, perform: { value in
+        EmergeModifierState.shared.expansionPreference = value
+      })
+      .onPreferenceChange(RenderingModePreferenceKey.self, perform: { value in
+        EmergeModifierState.shared.renderingMode = value
+      })
+      .onPreferenceChange(PrecisionPreferenceKey.self, perform: { value in
+        EmergeModifierState.shared.precision = value
+      })
+  }
+}

Sources/SnapshotPreferences/ExpansionPreference.swift

@@ -0,0 +1,25 @@
+//
+//  ExpansionPreference.swift
+//
+//
+//  Created by Noah Martin on 9/7/23.
+//
+
+import Foundation
+import SwiftUI
+
+struct ExpansionPreferenceKey: PreferenceKey {
+  static func reduce(value: inout Bool?, nextValue: () -> Bool?) {
+    if value == nil {
+      value = nextValue()
+    }
+  }
+
+  static var defaultValue: Bool? = nil
+}
+
+extension View {
+  public func emergeExpansion(_ enabled: Bool?) -> some View {
+    preference(key: ExpansionPreferenceKey.self, value: enabled)
+  }
+}

Sources/SnapshotPreferences/PrecisionPreference.swift

@@ -0,0 +1,23 @@
+//
+//  PrecisionPreference.swift
+//  
+//
+//  Created by Noah Martin on 9/5/23.
+//
+
+import Foundation
+import SwiftUI
+
+struct PrecisionPreferenceKey: PreferenceKey {
+  static func reduce(value: inout Float?, nextValue: () -> Float?) {
+    value = nextValue()
+  }
+
+  static var defaultValue: Float? = nil
+}
+
+extension View {
+  public func emergeSnapshotPrecision(_ precision: Float?) -> some View {
+    preference(key: PrecisionPreferenceKey.self, value: precision)
+  }
+}

Sources/SnapshotPreferences/RenderingModePreference.swift

@@ -0,0 +1,24 @@
+//
+//  RenderingModePreference.swift
+//
+//
+//  Created by Noah Martin on 9/7/23.
+//
+
+import Foundation
+import SwiftUI
+import SnapshotPreviewsCore
+
+struct RenderingModePreferenceKey: PreferenceKey {
+  static func reduce(value: inout Int?, nextValue: () -> Int?) {
+    value = nextValue()
+  }
+
+  static var defaultValue: EmergeRenderingMode.RawValue? = nil
+}
+
+extension View {
+  public func emergeRenderingMode(_ renderingMode: EmergeRenderingMode?) -> some View {
+    preference(key: RenderingModePreferenceKey.self, value: renderingMode?.rawValue)
+  }
+}

Sources/SnapshotPreviewsCore/ExpandingViewController.swift

@@ -34,19 +34,28 @@ extension UIView {
   }
 }
 
-public final class ExpandingViewController<Content: View>: UIHostingController<Content> {
+let modifierFinderClass = (NSClassFromString("EmergeModifierFinder") as? NSObject.Type)?.init()
+let finder = modifierFinderClass != nil ? Mirror(reflecting: modifierFinderClass!).descendant("finder") as? (any View) -> any View : nil
+let modifierState = NSClassFromString("EmergeModifierState") as? NSObject.Type
+let stateMirror = modifierState != nil ? Mirror(
+  reflecting: modifierState!
+    .perform(NSSelectorFromString("shared"))
+    .takeUnretainedValue()) : nil
+
+public final class ExpandingViewController<Content: View>: UIHostingController<AnyView> {
 
   private var didCall = false
   private var previousHeight: CGFloat?
   private let supportsExpansion: Bool
 
   private var heightAnchor: NSLayoutConstraint?
 
-  var expansionSettled: (() -> Void)?
+  var expansionSettled: ((EmergeRenderingMode?, Float?) -> Void)?
 
   init(rootView: Content, layout: PreviewLayout, supportsExpansion: Bool) {
     self.supportsExpansion = supportsExpansion
-    super.init(rootView: rootView)
+    let newView = finder?(rootView)
+    super.init(rootView: newView != nil ? AnyView(newView!) : AnyView(rootView))
 
     switch layout {
     case let .fixed(width: width, height: height):
@@ -63,12 +72,14 @@ public final class ExpandingViewController<Content: View>: UIHostingController<C
   @MainActor required dynamic init?(coder aDecoder: NSCoder) {
     fatalError("init(coder:) has not been implemented")
   }
-  
+
   private func runCallback() {
     guard !didCall else { return }
 
     didCall = true
-    expansionSettled?()
+    let renderingMode = stateMirror?.descendant("renderingMode") as? EmergeRenderingMode.RawValue
+    let emergeRenderingMode = renderingMode != nil ? EmergeRenderingMode(rawValue: renderingMode!) : nil
+    expansionSettled?(emergeRenderingMode, stateMirror?.descendant("precision") as? Float)
   }
 
   public override func viewDidLayoutSubviews() {
@@ -83,6 +94,9 @@ public final class ExpandingViewController<Content: View>: UIHostingController<C
       return
     }
 
+    let expansionPreference = stateMirror?.descendant("expansionPreference") as? Bool
+
+    let supportsExpansion = expansionPreference ?? self.supportsExpansion
     let scrollView = view.firstScrollView
     if let scrollView, supportsExpansion {
       let diff = Int(scrollView.contentSize.height - scrollView.visibleContentHeight)

Sources/SnapshotPreviewsCore/RenderingMode.swift

@@ -0,0 +1,15 @@
+//
+//  EmergeRenderingMode.swift
+//  
+//
+//  Created by Noah Martin on 10/6/23.
+//
+
+import Foundation
+
+public enum EmergeRenderingMode: Int {
+  // Renders using CALayer render(in:)
+  case coreAnimation
+  // Renders using UIView drawHierarchy(in: , afterScreenUpdates: true)
+  case uiView
+}

Sources/SnapshotPreviewsCore/SnapshotPreviewsCore.swift

@@ -13,7 +13,7 @@ public struct Preview: Identifiable {
     displayName = preview.displayName
     device = preview.device
     layout = preview.layout
-    let _view = {
+    _view = {
       let children = try extraction.previews.get()
 
       let (v, modifiers) = children[preview.id]
@@ -23,7 +23,6 @@ public struct Preview: Identifiable {
       }
       return AnyView(result)
     }
-    self._view = _view
   }
 
 #if swift(>=5.9)

Sources/SnapshotPreviewsCore/View+Snapshot.swift

@@ -17,16 +17,16 @@ extension View {
   public func snapshot(
     layout: PreviewLayout,
     window: UIWindow,
-    supportsExpansion: Bool,
-    renderingMode: EmergeRenderingMode?,
+    legacySupportsExpansion: Bool,
+    legacyRenderingMode: EmergeRenderingMode?,
     async: Bool,
-    completion: @escaping (Result<UIImage, Error>) -> Void)
+    completion: @escaping (Result<UIImage, Error>, Float?) -> Void)
   {
     UIView.setAnimationsEnabled(false)
     let animationDisabledView = self.transaction { transaction in
       transaction.disablesAnimations = true
     }
-    let controller = ExpandingViewController(rootView: animationDisabledView, layout: layout, supportsExpansion: supportsExpansion)
+    let controller = ExpandingViewController(rootView: animationDisabledView, layout: layout, supportsExpansion: legacySupportsExpansion)
     if #available(iOS 16, *) {
       controller.sizingOptions = .intrinsicContentSize
     }
@@ -37,14 +37,14 @@ extension View {
 
     let (windowRootVC, containerVC) = Self.setupRootVC(subVC: controller)
     window.rootViewController = windowRootVC
-    controller.expansionSettled = {
+    controller.expansionSettled = { renderingMode, precision in
       if async {
         DispatchQueue.main.asyncAfter(deadline: .now() + 2) {
-          completion(Self.takeSnapshot(layout: layout, renderingMode: renderingMode, rootVC: containerVC, controller: controller))
+          completion(Self.takeSnapshot(layout: layout, renderingMode: legacyRenderingMode ?? renderingMode, rootVC: containerVC, controller: controller), precision)
         }
       } else {
         DispatchQueue.main.async {
-          completion(Self.takeSnapshot(layout: layout, renderingMode: renderingMode, rootVC: containerVC, controller: controller))
+          completion(Self.takeSnapshot(layout: layout, renderingMode: legacyRenderingMode ?? renderingMode, rootVC: containerVC, controller: controller), precision)
         }
       }
     }

Sources/SnapshottingSwift/Snapshots.swift

@@ -114,21 +114,21 @@ class Snapshots {
 
     let provider = previewTypes[0]
     let preview = provider.previews.filter { $0.previewId == id }[0]
-    try! display(preview: preview) { imageResult in
+    try! display(preview: preview) { imageResult, _ in
       completion(imageResult, preview)
     }
   }
 
-  @MainActor func display(preview: SnapshotPreviewsCore.Preview, completion: @escaping (Result<UIImage, Error>) -> Void) throws {
+  @MainActor func display(preview: SnapshotPreviewsCore.Preview, completion: @escaping (Result<UIImage, Error>, Float?) -> Void) throws {
     var view = try preview.view()
     let supportsExpansion = ViewInspection.shouldExpand(view)
     let renderingMode = ViewInspection.renderingMode(of: view)
     view = AnyView(PreferredColorSchemeWrapper { view })
     view.snapshot(
       layout: preview.layout,
       window: window,
-      supportsExpansion: supportsExpansion,
-      renderingMode: renderingMode,
+      legacySupportsExpansion: supportsExpansion,
+      legacyRenderingMode: renderingMode,
       async: false,
       completion: completion)
   }