prototype for perf swiftUI trace

Author: themiswang

FirebasePerformance/Sources/SwiftUI/PerfTracedView.swift

@@ -0,0 +1,151 @@
+// Copyright 2025 Google LLC
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+#if canImport(SwiftUI)
+  import FirebasePerformance
+  import Foundation
+  import SwiftUI
+
+  // foregroud trace, screen render, refresh times
+  // background trace, duration
+  class PerfTraceViewModel {
+    enum TraceType: String {
+      case forground
+      case background
+    }
+
+    let name: String
+    var trace: Trace?
+    var traceType: TraceType?
+
+    var refreshCount: Int64 = 0
+
+    lazy var displayLink: CADisplayLink = .init(target: self, selector: #selector(displayLinkStep))
+    var previousTimestamp: CFTimeInterval = -1.0
+    var slowFrameCount: Int64 = 0
+    var totalFrameCount: Int64 = 0
+
+    init(name: String) {
+      self.name = name
+    }
+
+    func startScreenRenderMonitoring() {
+      displayLink.add(to: .main, forMode: .common)
+    }
+
+    func stopScreenRenderMonitoring() {
+      displayLink.remove(from: .main, forMode: .common)
+    }
+
+    // calling perf to start the trace
+    func startTrace(_ traceType: TraceType) {
+      if trace != nil {
+        print("there is active trace already, can't start another one")
+      }
+      self.traceType = traceType
+      trace = Performance().trace(name: "\(name)_\(traceType.rawValue)")
+      print("trace start \(name)")
+      trace?.start()
+      if self.traceType == .forground {
+        startScreenRenderMonitoring()
+      }
+    }
+
+    // calling perf to end the trace
+    func endTrace() {
+      print("trace end")
+      if traceType == .forground {
+        stopScreenRenderMonitoring()
+        trace?.setValue(totalFrameCount, forMetric: "totalFrameCount")
+        trace?.setValue(slowFrameCount, forMetric: "slowFrameCount")
+      }
+      trace?.stop()
+      trace = nil
+      traceType = nil
+      refreshCount = 0
+    }
+
+    func logChanges() {
+      refreshCount = refreshCount + 1
+      print("refresh count changed to: \(refreshCount)")
+      trace?.setValue(refreshCount, forMetric: "refreshCount")
+    }
+
+    @objc
+    func displayLinkStep() {
+      let currentTimestamp = displayLink.timestamp
+      if previousTimestamp > 0 {
+        let frameDuration = currentTimestamp - previousTimestamp
+        if frameDuration > 1.0 / 59.0 {
+          slowFrameCount += 1
+        }
+      }
+      totalFrameCount += 1
+      previousTimestamp = currentTimestamp
+    }
+  }
+
+  public struct PerfTracedView<Content: View>: View {
+    @State private var viewModel: PerfTraceViewModel
+
+    let content: () -> Content
+
+    // Init through view builder
+    public init(_ viewName: String, @ViewBuilder content: @escaping () -> Content) {
+      self.content = content
+      // print("Type of this content is: \(content()) ")
+      viewModel = PerfTraceViewModel(name: viewName)
+    }
+
+    @Environment(\.scenePhase) var scenePhase
+
+    public var body: some View {
+      viewModel.logChanges()
+
+      return content()
+        .onAppear {
+          print("\(viewModel.name) On appear \(Date().timeIntervalSince1970)")
+          viewModel.startTrace(.forground)
+        }
+        .onDisappear {
+          print("\(viewModel.name) On disaappear \(Date().timeIntervalSince1970)")
+          viewModel.endTrace()
+        }
+        .onChange(of: scenePhase) { oldValue, newPhase in
+          if newPhase == .active {
+            print("\(viewModel.name) Active \(Date().timeIntervalSince1970)")
+            if viewModel.traceType == .forground {
+              print("foreground trace already running")
+            } else {
+              viewModel.endTrace()
+              viewModel.startTrace(.forground)
+            }
+          } else if newPhase == .inactive {
+            print("\(viewModel.name) Inactive \(Date().timeIntervalSince1970)")
+            viewModel.endTrace()
+            viewModel.startTrace(.background)
+          } else if newPhase == .background {
+            print("\(viewModel.name) Background \(Date().timeIntervalSince1970)")
+          }
+        }
+    }
+  }
+
+  public extension View {
+    func perfTrace(_ viewName: String) -> some View {
+      return PerfTracedView(viewName) {
+        self
+      }
+    }
+  }
+#endif

Package.swift

@@ -924,6 +924,8 @@ let package = Package(
     .target(
       name: "FirebasePerformanceTarget",
       dependencies: [.target(name: "FirebasePerformance",
+                             condition: .when(platforms: [.iOS, .tvOS, .visionOS])),
+                     .target(name: "FirebasePerformanceSwift",
                              condition: .when(platforms: [.iOS, .tvOS, .visionOS]))],
       path: "SwiftPM-PlatformExclude/FirebasePerformanceWrap"
     ),
@@ -943,7 +945,12 @@ let package = Package(
         .product(name: "GULUserDefaults", package: "GoogleUtilities"),
         .product(name: "nanopb", package: "nanopb"),
       ],
-      path: "FirebasePerformance/Sources",
+      path: "FirebasePerformance",
+      source: [
+        "Sources/",
+      ],
+      exclude:
+      ["Sources/SwiftUI/"],
       publicHeadersPath: "Public",
       cSettings: [
         .headerSearchPath("../../"),
@@ -957,6 +964,11 @@ let package = Package(
         .linkedFramework("QuartzCore", .when(platforms: [.iOS, .tvOS])),
       ]
     ),
+    .tartget(
+      name: "FirebasePerformanceSwift",
+      dependencies: ["FirebasePerformance"],
+      path: "FirebasePerformance/Sources/SwiftUI/"
+    ),
     .testTarget(
       name: "PerformanceUnit",
       dependencies: [