长章节内存优化 P1：章节级共享显示内容与 layouter，高亮转 overlay

- 新增 RDEPUBChapterDisplayContentCache（LRU 2，主线程限定，控制器
  持有）：整章显示串构建时一次性注入全章主题色与暗黑图替换，配套
  共享 DTCoreTextLayouter；签名 = 章节内容对象标识 + 主题双色 +
  暗黑图配置，设置/主题变化自动失效重建
- RDEPUBTextContentView.configure 改为引用共享 entry，删除每次翻页
  的整章可变拷贝与按页属性写入
- 高亮/下划线改走 overlay decoration（高亮背景层、下划线前景层），
  移除 applyHighlightsToContent 与 render view 的属性绘制路径，
  高亮增删不再触发整章重建
- 内存警告时清空 display cache；shouldAvoidReaderPageCaching 保持
  保守（P1-4 待真机数据）

验证：编译通过；高亮/批注/选区/翻页/设置 13 项 UI 回归全过。
SearchTests 10 项失败经二分确认为先存回归（5a41066 与 e4e629a 均
复现，最后已知通过为 2026-06-08），与本次改动无关，待单独排查。

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

Doc/LONG_CHAPTER_MEMORY_OPTIMIZATION_PLAN.md

@@ -61,28 +61,26 @@
 
 **任务**：
 
-- [ ] 在章节运行时侧（建议挂在 `RDEPUBRuntimeChapter` 或新建 `RDEPUBChapterDisplayCache`）新增：
-  - `chapterDisplayContent`（`typesetAttributedString` 的一次性拷贝）
-  - `displaySignature`（组成：主题、暗黑图配置、字体设置、本章高亮集合版本）
-- [ ] 构建共享内容时一次性注入：全章范围主题色；全章范围高亮/下划线属性（若 P1-2 决定转 overlay 则此项取消）
-- [ ] 确定暗黑图策略（二选一）：
-  - a. 构建时全章一次性替换（依赖 `RDEPUBDarkImageAdjuster` 的 NSCache 兜底解码成本）
-  - b. 移到渲染时按可见附件替换，不触碰共享字符串
-- [ ] `RDEPUBTextContentView.configure` 改为接收"共享内容引用 + `page.contentRange`"，删除 443 行的整章拷贝
-- [ ] 高亮增删、搜索激活、主题/设置变化 → 比对 `displaySignature`，不一致则重建共享内容（禁止原地修改）
-- [ ] 章节淘汰（`RDEPUBChapterRuntimeStore.evict` / `handleMemoryWarning` / `invalidateAllForSettingsChange`）同步释放 display cache
+- [x] 已新建 `RDEPUBChapterDisplayContentCache`（LRU 容量 2，主线程限定，`RDEPUBReaderController` 持有）：`content` + `layouter` + `signature`
+- [x] 构建共享内容时一次性注入：全章范围主题色；高亮/下划线因 P1-2 转 overlay，不进共享内容也不进签名
+- [x] 暗黑图策略选 a：构建时全章一次性替换，复用 `RDEPUBDarkImageAdjuster` 的 NSCache
+- [x] `RDEPUBTextContentView.configure` 已改为接收 `displayCache` 参数并引用共享 entry，整章拷贝已删除
+- [x] 签名 = 章节内容对象标识 + 长度 + 主题双色 + 暗黑图配置；设置/主题变化经签名自动失效重建（高亮变化不触发重建，仅重建 overlay 装饰）
+- [x] 控制器在 `didReceiveMemoryWarning` 清空 display cache；设置变更重建 chapterContent 实例后由签名兜底换代
 
 **验收**：连续翻页不再出现整章拷贝（打点确认）；翻页延迟下降；高亮显示、高亮点击菜单、underline、搜索 currentMatch、附件点击、选区拖拽全部回归通过。
 
+> 2026-07-08 回归记录：高亮/批注/选区/翻页/设置 13 项 UI 用例全过；SearchTests 10 项失败，但已在会话前提交 5a41066 与 P0 提交 e4e629a 上复现同样失败（搜索 0 命中），确认为先于本优化存在的独立回归（最后一次已知通过是 2026-06-08 全量跑），需单独排查，与 P1 改动无关。
+
 ### P1-2 高亮/下划线剥离为 overlay（与 P1-1 绑定）
 
 **现状**：搜索高亮已走 overlay（`RDEPUBTextContentView.swift:759` 处 `buildDecorations` 传 `highlights: []`，注释明确为避免双画）；普通高亮/下划线仍靠写 `kRDEPUBHighlightAttributeName` / `kRDEPUBUnderlineAttributeName` 属性由 render view 绘制。
 
 **任务**：
 
-- [ ] `buildDecorations` 改为传入真实 highlights，高亮/下划线由 decoration 层绘制
-- [ ] 移除 `applyHighlightsToContent`（`RDEPUBTextContentView.swift:617`）及 render view 对两个自定义属性的绘制路径，确认无双画
-- [ ] 高亮命中（`highlight(at:)`）与菜单锚点继续走 `interactionController.selectionRects`，坐标保持 chapter-absolute
+- [x] `buildDecorations` 已传入真实 highlights，高亮进背景层（文字下方）、下划线进前景层
+- [x] `applyHighlightsToContent` 与 render view 的 `drawHighlights`/`computeHighlightRects`/`attributedDisplayContent` 已整体移除，无双画
+- [x] 高亮命中与菜单锚点继续走 `interactionController.selectionRects`，坐标保持 chapter-absolute（未改动）
 
 **验收**：高亮/下划线视觉与改前一致（含跨页高亮的页内裁剪）；高亮点击弹菜单正常；与搜索高亮叠加时无双画。
 
@@ -92,10 +90,10 @@
 
 **任务**：
 
-- [ ] `DTCoreTextLayouter` 随 `chapterDisplayContent` 一起放入章节级 display cache，与 signature 同生命周期
-- [ ] 页面按 `bounds` + `page.contentRange` 取 `layoutFrame`；`RDEPUBTextPageVerticalJustifier.justify` 会修改 layoutFrame，因此 **保持 `shouldCacheLayoutFrames = false`**，layoutFrame 永远按页新建、不共享
-- [ ] bounds 变化（横竖屏/双页）纳入失效条件；确认旧 layoutFrame 随页面视图释放
-- [ ] `RDEPUBTextPageBoundaryValidator` 校验路径不变
+- [x] `DTCoreTextLayouter` 已随共享内容放入 display cache，与 signature 同生命周期
+- [x] 页面按 `bounds` + `page.contentRange` 取 `layoutFrame`；`shouldCacheLayoutFrames = false` 保持，layoutFrame 按页新建（VerticalJustifier 的修改不会污染共享对象）
+- [x] framesetter 只依赖字符串、与 bounds 无关，bounds 变化无需失效共享对象；layoutFrame 随页面视图释放
+- [x] `RDEPUBTextPageBoundaryValidator` 校验路径不变
 
 **验收**：翻页时不再重建 framesetter（打点确认）；横竖屏切换后布局正确；`--demo-pagination-validate` 不回升。
 

Sources/RDReaderView/EPUBUI/RDEPUBReaderController+DataSource.swift

@@ -64,7 +64,8 @@ extension RDEPUBReaderController: RDReaderDataSource, RDReaderPageProvider, RDRe
                     chapterCFIMap: resolvedPage.chapter.chapterOffsetMap.cfiMap,
                     chapterFragmentOffsets: resolvedPage.chapter.chapterOffsetMap.fragmentOffsets,
                     highlights: textHighlights(for: resolvedPage.page),
-                    searchState: searchState(for: resolvedPage.page)
+                    searchState: searchState(for: resolvedPage.page),
+                    displayCache: textDisplayCache
                 )
                 return contentView
             }
@@ -108,7 +109,8 @@ extension RDEPUBReaderController: RDReaderDataSource, RDReaderPageProvider, RDRe
                 chapterCFIMap: textBook.chapterData(for: page.href)?.chapter.cfiMap,
                 chapterFragmentOffsets: textBook.chapterData(for: page.href)?.chapter.fragmentOffsets ?? [:],
                 highlights: textHighlights(for: page),
-                searchState: searchState(for: page)
+                searchState: searchState(for: page),
+                displayCache: textDisplayCache
             )
             return contentView
         }

Sources/RDReaderView/EPUBUI/RDEPUBReaderController.swift

@@ -96,6 +96,10 @@ public final class RDEPUBReaderController: UIViewController {
 
     let paginationHostView = UIView()
 
+    /// Chapter-level shared display content/layouter for text pages
+    /// (LONG_CHAPTER_MEMORY_OPTIMIZATION_PLAN.md P1-1/P1-3).
+    let textDisplayCache = RDEPUBChapterDisplayContentCache()
+
     lazy var readerContext = RDEPUBReaderContext(controller: self)
 
     var parser: RDEPUBParser? {
@@ -292,6 +296,7 @@ public final class RDEPUBReaderController: UIViewController {
     public override func didReceiveMemoryWarning() {
         super.didReceiveMemoryWarning()
         runtime.handleMemoryWarning()
+        textDisplayCache.removeAll()
     }
 
     public override func viewWillTransition(to size: CGSize, with coordinator: UIViewControllerTransitionCoordinator) {

Sources/RDReaderView/EPUBUI/TextPage/RDEPUBChapterDisplayContentCache.swift

@@ -0,0 +1,114 @@
+import UIKit
+
+#if canImport(DTCoreText)
+import DTCoreText
+#endif
+
+/// Chapter-level shared display content and layouter
+/// (LONG_CHAPTER_MEMORY_OPTIMIZATION_PLAN.md P1-1 / P1-3).
+///
+/// One entry holds the chapter-length display string (theme text color and
+/// dark-image adjustment injected once over the full chapter at build time)
+/// plus the DTCoreTextLayouter wrapping its framesetter. Page views reference
+/// the shared string and request per-page layout frames; they must never
+/// mutate the shared string — the framesetter and any live layout frame hold
+/// it. Page-level decoration (highlights, search, selection) is drawn by the
+/// overlay views instead.
+///
+/// Main-thread only.
+final class RDEPUBChapterDisplayContentCache {
+
+#if canImport(DTCoreText)
+
+    struct Entry {
+        let content: NSAttributedString
+        let layouter: DTCoreTextLayouter?
+        fileprivate let signature: Signature
+    }
+
+    fileprivate struct Signature: Equatable {
+        let chapterContentID: ObjectIdentifier
+        let contentLength: Int
+        let textColor: UIColor
+        let backgroundColor: UIColor
+        let darkImageAdjustmentEnabled: Bool
+        let darkImageBlendRatio: CGFloat
+
+        init(page: RDEPUBTextPage, configuration: RDEPUBReaderConfiguration) {
+            chapterContentID = ObjectIdentifier(page.chapterContent)
+            contentLength = page.chapterContent.length
+            textColor = configuration.theme.contentTextColor
+            backgroundColor = configuration.theme.contentBackgroundColor
+            darkImageAdjustmentEnabled = configuration.darkImageAdjustmentEnabled
+            darkImageBlendRatio = configuration.darkImageBlendRatio
+        }
+    }
+
+    /// Current chapter plus one adjacent chapter during page-curl/scroll
+    /// transitions across a chapter boundary.
+    private static let capacity = 2
+
+    private var entries: [String: Entry] = [:]
+
+    private var accessOrder: [String] = []
+
+    func entry(for page: RDEPUBTextPage, configuration: RDEPUBReaderConfiguration) -> Entry {
+        dispatchPrecondition(condition: .onQueue(.main))
+        let signature = Signature(page: page, configuration: configuration)
+        if let cached = entries[page.href], cached.signature == signature {
+            touch(page.href)
+            return cached
+        }
+        let entry = Self.buildEntry(page: page, configuration: configuration, signature: signature)
+        entries[page.href] = entry
+        touch(page.href)
+        evictIfNeeded()
+        RDEPUBMemoryProbe.log("displayContentBuilt href=\(page.href) length=\(entry.content.length)")
+        return entry
+    }
+
+    func removeAll() {
+        entries.removeAll()
+        accessOrder.removeAll()
+    }
+
+    private func touch(_ href: String) {
+        accessOrder.removeAll { $0 == href }
+        accessOrder.append(href)
+    }
+
+    private func evictIfNeeded() {
+        while accessOrder.count > Self.capacity {
+            let evicted = accessOrder.removeFirst()
+            entries.removeValue(forKey: evicted)
+        }
+    }
+
+    private static func buildEntry(
+        page: RDEPUBTextPage,
+        configuration: RDEPUBReaderConfiguration,
+        signature: Signature
+    ) -> Entry {
+        let content = NSMutableAttributedString(attributedString: page.chapterContent)
+        let fullRange = NSRange(location: 0, length: content.length)
+        _ = RDEPUBDarkImageAdjuster.adjustIfNeeded(
+            content,
+            in: fullRange,
+            configuration: configuration
+        )
+        content.addAttribute(
+            .foregroundColor,
+            value: configuration.theme.contentTextColor,
+            range: fullRange
+        )
+        let layouter = DTCoreTextLayouter(attributedString: content)
+        layouter?.shouldCacheLayoutFrames = false
+        return Entry(content: content, layouter: layouter, signature: signature)
+    }
+
+#else
+
+    func removeAll() {}
+
+#endif
+}

Sources/RDReaderView/EPUBUI/TextPage/RDEPUBTextContentView.swift

@@ -87,12 +87,16 @@ final class RDEPUBTextContentView: UIView, UIGestureRecognizerDelegate, RDReader
         return view
     }()
 
+    /// Chapter-level shared display string owned by the display cache.
+    /// Read-only from the page's perspective: theme color and dark-image
+    /// adjustment are baked in at build time; page decoration goes through
+    /// the overlay views.
     private var coreTextDisplayContent: NSAttributedString?
 
     private var coreTextDisplayRange: NSRange?
 
-    /// Framesetter over the full chapter copy, rebuilt when the display
-    /// content changes; layout frames are recomputed per bounds change.
+    /// Shared chapter-level layouter (owned by the display cache); layout
+    /// frames are recomputed per page range and bounds change.
     private var coreTextLayouter: DTCoreTextLayouter?
 #endif
 
@@ -397,7 +401,8 @@ final class RDEPUBTextContentView: UIView, UIGestureRecognizerDelegate, RDReader
         chapterCFIMap: RDEPUBCFIMap? = nil,
         chapterFragmentOffsets: [String: Int] = [:],
         highlights: [RDEPUBHighlight] = [],
-        searchState: RDEPUBSearchState? = nil
+        searchState: RDEPUBSearchState? = nil,
+        displayCache: RDEPUBChapterDisplayContentCache? = nil
     ) {
         loadingSpinner.stopAnimating()
         currentPage = page
@@ -437,37 +442,26 @@ final class RDEPUBTextContentView: UIView, UIGestureRecognizerDelegate, RDReader
         coverImageView.image = nil
 
 #if canImport(DTCoreText)
-        // In-context display: keep the full chapter string and lay out only the
-        // page's range. CTTypesetter line breaks are context-sensitive, so
+        // In-context display: lay out the full chapter string and render only
+        // the page's range. CTTypesetter line breaks are context-sensitive, so
         // re-wrapping a page substring can break ±1 character away from the
         // paginator's line ends (lone characters spilling onto the last line);
         // laying out the same chapter string the paginator used cannot.
         // String indices in the layout frame are therefore chapter-absolute.
-        let displayContent = NSMutableAttributedString(attributedString: page.chapterContent)
+        // The chapter string and layouter are shared per chapter via the
+        // display cache; this view must not mutate the shared string.
+        let display = (displayCache ?? RDEPUBChapterDisplayContentCache())
+            .entry(for: page, configuration: configuration)
         let pageRange = NSIntersectionRange(
             page.contentRange,
-            NSRange(location: 0, length: displayContent.length)
+            NSRange(location: 0, length: display.content.length)
         )
-        _ = RDEPUBDarkImageAdjuster.adjustIfNeeded(
-            displayContent,
-            in: pageRange,
-            configuration: configuration
-        )
-        displayContent.addAttribute(
-            .foregroundColor,
-            value: configuration.theme.contentTextColor,
-            range: pageRange
-        )
-
-        applyHighlightsToContent(displayContent, highlights: highlights, page: page)
         coreTextContentView.isHidden = false
         coreTextContentView.backgroundColor = .clear
         coreTextContentView.accessibilityIdentifier = "epub.reader.selection.text"
-        coreTextDisplayContent = displayContent
+        coreTextDisplayContent = display.content
         coreTextDisplayRange = pageRange
-        coreTextLayouter = DTCoreTextLayouter(attributedString: displayContent)
-        coreTextLayouter?.shouldCacheLayoutFrames = false
-        coreTextContentView.attributedDisplayContent = displayContent
+        coreTextLayouter = display.layouter
         updateCoreTextLayoutFrameIfNeeded()
 #else
         let selectionContent = normalizedPageContent(from: page)
@@ -521,7 +515,6 @@ final class RDEPUBTextContentView: UIView, UIGestureRecognizerDelegate, RDReader
 #if canImport(DTCoreText)
         coreTextContentView.isHidden = false
         coreTextContentView.backgroundColor = .clear
-        coreTextContentView.attributedDisplayContent = nil
         coreTextContentView.layoutFrame = nil
         coreTextDisplayContent = nil
         coreTextDisplayRange = nil
@@ -615,31 +608,6 @@ final class RDEPUBTextContentView: UIView, UIGestureRecognizerDelegate, RDReader
         return image(from: attachmentValue)
     }
 
-    /// Marks highlight ranges on the chapter-length display copy. Ranges stay
-    /// chapter-absolute — the in-context layout frame uses the same indices.
-    private func applyHighlightsToContent(
-        _ content: NSMutableAttributedString,
-        highlights: [RDEPUBHighlight],
-        page: RDEPUBTextPage
-    ) {
-        for highlight in highlights {
-            guard highlight.location.href == page.href else { continue }
-            guard let rangeInfo = highlight.rangeInfo,
-                  let info = RDEPUBTextOffsetRangeInfo.decode(from: rangeInfo),
-                  let absoluteRange = info.nsRange else { continue }
-            let overlap = NSIntersectionRange(absoluteRange, page.contentRange)
-            guard overlap.length > 0,
-                  overlap.location + overlap.length <= content.length else { continue }
-
-            switch highlight.style {
-            case .highlight:
-                content.addAttribute(kRDEPUBHighlightAttributeName, value: highlight.uiColor, range: overlap)
-            case .underline:
-                content.addAttribute(kRDEPUBUnderlineAttributeName, value: highlight.uiColor, range: overlap)
-            }
-        }
-    }
-
     private func normalizedPageContent(from page: RDEPUBTextPage) -> NSMutableAttributedString {
         let content = NSMutableAttributedString(attributedString: page.content)
         guard content.length > 0 else { return content }
@@ -759,12 +727,12 @@ final class RDEPUBTextContentView: UIView, UIGestureRecognizerDelegate, RDReader
         backgroundOverlayView.updateSnapshot(interactionController.snapshot)
 
         if let page = currentPage {
+            // Highlights/underlines and search are all drawn as overlay
+            // decorations; the shared chapter display string carries no
+            // page-level annotation attributes.
             let (bgDecorations, fgDecorations) = overlayView.buildDecorations(
                 page: page,
-                // Text-page highlights/underlines are already painted by the
-                // CoreText render view via display-content attributes. Keep
-                // overlay decorations for search only to avoid double drawing.
-                highlights: [],
+                highlights: currentHighlights,
                 searchState: currentSearchState,
                 interactionController: interactionController
             )

Sources/RDReaderView/EPUBUI/TextPage/RDEPUBTextPageRenderView.swift

@@ -22,12 +22,6 @@ final class RDEPUBTextPageRenderView: UIView {
         }
     }
 
-    var attributedDisplayContent: NSAttributedString? {
-        didSet {
-            invalidateStaticContent()
-        }
-    }
-
     var selectionRects: [CGRect] = [] {
         didSet {
             setNeedsDisplay()
@@ -78,9 +72,6 @@ final class RDEPUBTextPageRenderView: UIView {
         if let cachedStaticImage {
             cachedStaticImage.draw(in: bounds)
         } else {
-            if let attributedDisplayContent {
-                drawHighlights(in: context, attributedString: attributedDisplayContent, layoutFrame: layoutFrame)
-            }
             layoutFrame.draw(in: context, options: drawOptions)
         }
 
@@ -96,59 +87,6 @@ final class RDEPUBTextPageRenderView: UIView {
         }
     }
 
-    private func drawHighlights(
-        in context: CGContext,
-        attributedString: NSAttributedString,
-        layoutFrame: DTCoreTextLayoutFrame
-    ) {
-        let fullRange = NSRange(location: 0, length: attributedString.length)
-
-        attributedString.enumerateAttribute(kRDEPUBHighlightAttributeName, in: fullRange) { value, range, _ in
-            guard let color = value as? UIColor else { return }
-            let rects = computeHighlightRects(for: range, layoutFrame: layoutFrame)
-            color.setFill()
-            for rect in rects {
-                context.fill(rect)
-            }
-        }
-
-        attributedString.enumerateAttribute(kRDEPUBUnderlineAttributeName, in: fullRange) { value, range, _ in
-            guard let color = value as? UIColor else { return }
-            let rects = computeHighlightRects(for: range, layoutFrame: layoutFrame)
-            color.setStroke()
-            context.setLineWidth(2)
-            for rect in rects {
-                let y = rect.maxY - 1
-                context.move(to: CGPoint(x: rect.minX, y: y))
-                context.addLine(to: CGPoint(x: rect.maxX, y: y))
-                context.strokePath()
-            }
-        }
-    }
-
-    private func computeHighlightRects(for range: NSRange, layoutFrame: DTCoreTextLayoutFrame) -> [CGRect] {
-        var rects: [CGRect] = []
-        guard let lines = layoutFrame.lines as? [DTCoreTextLayoutLine] else { return rects }
-
-        for line in lines {
-            let lineRange = line.stringRange()
-            let overlap = NSIntersectionRange(range, lineRange)
-            guard overlap.length > 0 else { continue }
-
-            let startX = line.offset(forStringIndex: overlap.location)
-            let endX = line.offset(forStringIndex: overlap.location + overlap.length)
-            let rect = CGRect(
-                x: line.baselineOrigin.x + startX,
-                y: line.baselineOrigin.y - line.ascent,
-                width: endX - startX,
-                height: line.ascent + line.descent
-            )
-            rects.append(rect)
-        }
-
-        return rects
-    }
-
     private func drawSelection(in context: CGContext) {
         guard !selectionRects.isEmpty else { return }
         selectionColor.setFill()
@@ -261,9 +199,6 @@ final class RDEPUBTextPageRenderView: UIView {
         let renderer = UIGraphicsImageRenderer(size: bounds.size, format: format)
         return renderer.image { _ in
             guard let staticContext = UIGraphicsGetCurrentContext() else { return }
-            if let attributedDisplayContent {
-                drawHighlights(in: staticContext, attributedString: attributedDisplayContent, layoutFrame: layoutFrame)
-            }
             layoutFrame.draw(in: staticContext, options: drawOptions)
         }
     }