DesignProbe

DesignProbe.swift

import SwiftUI

// 设计锚点：在 Preview 渲染进程内收集元素坐标并写成 JSON，替代模拟器中的 XCUI 层级采集。

struct DesignAnchorEntry {
    let id: String
    let instance: String?
    let label: String?
    let bounds: Anchor<CGRect>
}

struct DesignAnchorKey: PreferenceKey {
    static let defaultValue: [DesignAnchorEntry] = []

    static func reduce(value: inout [DesignAnchorEntry], nextValue: () -> [DesignAnchorEntry]) {
        value.append(contentsOf: nextValue())
    }
}

extension View {
    /// 同时设置 accessibilityIdentifier 与设计锚点；instance 用于区分列表中的同一组件。
    func designAnchor(_ id: String, instance: String? = nil, label: String? = nil) -> some View {
        accessibilityIdentifier(id)
            // anchorPreference 会覆盖子视图的值，嵌套锚点必须用 transform 版本追加
            .transformAnchorPreference(key: DesignAnchorKey.self, value: .bounds) { value, anchor in
                value.append(DesignAnchorEntry(id: id, instance: instance, label: label, bounds: anchor))
            }
    }

    /// 放在节点根视图上：把锚点坐标（window 坐标系，单位 pt）写到宿主机目录。
    /// build 是编译进这次构建的源码指纹（生成的 Preview 以类型名传入），随记录写回，供 FlowCanvas 核对截图来自哪一版代码。
    func designProbe(_ node: String, build: String? = nil) -> some View {
        modifier(DesignProbeModifier(node: node, build: build))
    }
}

private struct ProbeRecord: Codable, Equatable {
    let id: String
    let instance: String?
    let label: String?
    let frame: [Double]
}

private struct DesignProbeModifier: ViewModifier {
    static let screenRecord = "__screen"
    static let buildRecord = "__build"
    let node: String
    let build: String?
    @Environment(\.colorScheme) private var colorScheme
    @Environment(\.dynamicTypeSize) private var dynamicTypeSize

    func body(content: Content) -> some View {
        content.overlayPreferenceValue(DesignAnchorKey.self) { entries in
            GeometryReader { proxy in
                let origin = proxy.frame(in: .global).origin
                // 屏幕尺寸（pt）：根视图加上它的安全区，供 FlowCanvas 核对 Preview 实际按哪种设备渲染
                let insets = proxy.safeAreaInsets
                let screen = ProbeRecord(
                    id: Self.screenRecord, instance: nil, label: nil,
                    frame: [0, 0, origin.x + proxy.size.width + insets.trailing,
                            origin.y + proxy.size.height + insets.bottom].map { (Double($0) * 10).rounded() / 10 }
                )
                let fingerprint = build.map { ProbeRecord(id: Self.buildRecord, instance: nil, label: $0, frame: [0, 0, 0, 0]) }
                let records = [screen] + (fingerprint.map { [$0] } ?? []) + entries.map { entry in
                    let rect = proxy[entry.bounds]
                    let values: [CGFloat] = [rect.minX + origin.x, rect.minY + origin.y, rect.width, rect.height]
                    return ProbeRecord(
                        id: entry.id, instance: entry.instance, label: entry.label,
                        frame: values.map { (Double($0) * 10).rounded() / 10 }
                    )
                }
                Color.clear.task(id: records) {
                    write(records)
                }
            }
            .allowsHitTesting(false)
        }
    }

    private func write(_ records: [ProbeRecord]) {
        guard let home = ProcessInfo.processInfo.environment["SIMULATOR_HOST_HOME"] else { return }
        let dir = URL(filePath: home).appending(path: "Library/Caches/FlowCanvas/anchors")
        let name = "\(node)__\(colorScheme == .dark ? "dark" : "light")__\(dynamicTypeSize).json"
        try? FileManager.default.createDirectory(at: dir, withIntermediateDirectories: true)
        let encoder = JSONEncoder()
        encoder.outputFormatting = [.prettyPrinted, .sortedKeys]
        try? encoder.encode(records).write(to: dir.appending(path: name))
    }
}

/// 屏幕函数 `switch` 的 default 分支（原型规范 PG-10）：采集键没有对应屏幕时画出可见的占位，而不是空白页。
struct UnknownCaptureKey: View {
    let key: String

    var body: some View {
        ContentUnavailableView("没有这个采集键的屏幕", systemImage: "questionmark.square.dashed",
                               description: Text(key))
    }
}