309 lines
13 KiB
Swift
309 lines
13 KiB
Swift
import Foundation
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import UIKit
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/// 分页规则策略：语义边界搜索、行级保护检查、范围调整调度器。
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///
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/// 不构建 CoreText frame，只基于 attributed string 属性做规则判定。
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struct RDEPUBPageBreakPolicy {
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private let attributedString: NSAttributedString
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init(attributedString: NSAttributedString) {
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self.attributedString = attributedString
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}
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// MARK: - 行级保护检查
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/// 检查指定行范围是否落在 avoidPageBreakInside 保护块内。
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func lineIsInAvoidPageBreakInsideBlock(_ lineRange: NSRange) -> Bool {
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guard let probeRange = clampedProbeRange(for: lineRange) else {
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return false
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}
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var found = false
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attributedString.enumerateAttributes(in: probeRange) { attributes, _, stop in
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guard shouldTreatAvoidHintAsBlockProtection(attributes) else {
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return
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}
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guard let rawValue = attributes[.rdPageSemanticHints] as? String else { return }
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let hints = rawValue
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.split(separator: ",")
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.compactMap { RDEPUBTextSemanticHint(rawValue: String($0)) }
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if hints.contains(.avoidPageBreakInside) {
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found = true
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stop.pointee = true
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}
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}
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return found
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}
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/// 检查指定行范围是否落在 keepWithNext 保护块内。
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func lineIsInKeepWithNextBlock(_ lineRange: NSRange) -> Bool {
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guard let probeRange = clampedProbeRange(for: lineRange) else {
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return false
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}
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var found = false
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attributedString.enumerateAttribute(.rdPageSemanticHints, in: probeRange) { value, _, stop in
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guard let rawValue = value as? String else { return }
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let hints = rawValue
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.split(separator: ",")
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.compactMap { RDEPUBTextSemanticHint(rawValue: String($0)) }
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if hints.contains(.keepWithNext) {
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found = true
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stop.pointee = true
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}
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}
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return found
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}
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// MARK: - 范围调整调度器
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/// 对 CoreText/DTCoreText 提出的分页范围进行语义边界调整。
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///
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/// 调整优先级：
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/// 1. 若已达章节末尾，直接返回 chapterEnd
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/// 2. pageRelate 跨页关联边界
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/// 3. 以上都不满足时，使用原始帧限制分页
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func adjustedRange(
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from proposedRange: NSRange,
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totalLength: Int,
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lineRanges: [NSRange],
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factory: RDEPUBCoreTextPageFrameFactory
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) -> (
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range: NSRange,
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breakReason: RDEPUBTextPageBreakReason,
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blockRange: NSRange?,
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attachmentRanges: [NSRange],
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attachmentKinds: [RDEPUBTextAttachmentKind],
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blockKinds: [RDEPUBTextBlockKind],
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semanticHints: [RDEPUBTextSemanticHint],
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attachmentPlacements: [RDEPUBTextAttachmentPlacement],
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diagnostics: [String]
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) {
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let pageEnd = proposedRange.location + proposedRange.length
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let proposedBlockKinds = factory.blockKinds(in: proposedRange)
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let proposedSemanticHints = factory.semanticHints(in: proposedRange)
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let proposedAttachmentPlacements = factory.attachmentPlacements(in: proposedRange)
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guard pageEnd < totalLength else {
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return (
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range: proposedRange,
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breakReason: .chapterEnd,
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blockRange: factory.blockRange(at: max(proposedRange.location, pageEnd - 1)),
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attachmentRanges: factory.attachmentRanges(in: proposedRange),
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attachmentKinds: factory.attachmentKinds(in: proposedRange),
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blockKinds: proposedBlockKinds,
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semanticHints: proposedSemanticHints,
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attachmentPlacements: proposedAttachmentPlacements,
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diagnostics: factory.diagnostics(
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reason: .chapterEnd,
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range: proposedRange,
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attachmentRanges: factory.attachmentRanges(in: proposedRange),
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blockRange: factory.blockRange(at: max(proposedRange.location, pageEnd - 1)),
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blockKinds: proposedBlockKinds,
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semanticHints: proposedSemanticHints,
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attachmentPlacements: proposedAttachmentPlacements
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)
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)
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}
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let currentBlockRange = factory.blockRange(at: max(proposedRange.location, pageEnd - 1))
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let currentAttachmentRanges = factory.attachmentRanges(in: proposedRange)
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let currentAttachmentKinds = factory.attachmentKinds(in: proposedRange)
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let currentBlockKinds = proposedBlockKinds
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let currentSemanticHints = proposedSemanticHints
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let currentAttachmentPlacements = proposedAttachmentPlacements
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// 对齐 WXRead：默认按 CTFrame 已经容纳的行数分页，仅保留 pageRelate 这种
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// 微信读书特有的跨页关联规则。
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if let pageRelateBoundary = preferredPageRelateBoundary(
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after: proposedRange,
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minimumEnd: proposedRange.location + 1,
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lineRanges: lineRanges,
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factory: factory
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) {
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let adjustedRange = NSRange(location: proposedRange.location, length: pageRelateBoundary - proposedRange.location)
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return (
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range: adjustedRange,
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breakReason: .semanticBoundary,
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blockRange: currentBlockRange,
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attachmentRanges: currentAttachmentRanges,
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attachmentKinds: currentAttachmentKinds,
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blockKinds: currentBlockKinds,
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semanticHints: currentSemanticHints,
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attachmentPlacements: currentAttachmentPlacements,
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diagnostics: factory.diagnostics(
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reason: .semanticBoundary,
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range: adjustedRange,
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attachmentRanges: currentAttachmentRanges,
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blockRange: currentBlockRange,
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blockKinds: currentBlockKinds,
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semanticHints: currentSemanticHints,
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attachmentPlacements: currentAttachmentPlacements,
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trigger: RDEPUBTextSemanticHint.pageRelate.rawValue
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)
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)
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}
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// 帧限制（默认分页）
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return (
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range: proposedRange,
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breakReason: .frameLimit,
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blockRange: currentBlockRange,
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attachmentRanges: currentAttachmentRanges,
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attachmentKinds: currentAttachmentKinds,
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blockKinds: currentBlockKinds,
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semanticHints: currentSemanticHints,
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attachmentPlacements: currentAttachmentPlacements,
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diagnostics: factory.diagnostics(
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reason: .frameLimit,
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range: proposedRange,
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attachmentRanges: currentAttachmentRanges,
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blockRange: currentBlockRange,
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blockKinds: currentBlockKinds,
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semanticHints: currentSemanticHints,
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attachmentPlacements: currentAttachmentPlacements
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)
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)
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}
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// MARK: - 语义边界查找
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/// 在指定范围内查找最优的语义分页点（pageBreakBefore / pageBreakAfter）。
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func preferredSemanticBoundary(
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in range: NSRange,
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minimumEnd: Int,
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factory: RDEPUBCoreTextPageFrameFactory
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) -> (location: Int, trigger: String)? {
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guard let safeRange = factory.clampedRange(range), safeRange.length > 0 else {
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return nil
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}
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var boundary: (location: Int, trigger: String)?
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attributedString.enumerateAttribute(.rdPageSemanticHints, in: safeRange) { value, attributeRange, stop in
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guard let rawValue = value as? String else { return }
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let hints = rawValue
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.split(separator: ",")
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.compactMap { RDEPUBTextSemanticHint(rawValue: String($0)) }
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guard !hints.isEmpty else { return }
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if hints.contains(.pageBreakBefore),
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attributeRange.location > safeRange.location,
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attributeRange.location >= minimumEnd {
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boundary = (attributeRange.location, RDEPUBTextSemanticHint.pageBreakBefore.rawValue)
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stop.pointee = true
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return
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}
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let attributeEnd = attributeRange.location + attributeRange.length
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if hints.contains(.pageBreakAfter),
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attributeEnd > minimumEnd,
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attributeEnd < safeRange.location + safeRange.length {
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boundary = (attributeEnd, RDEPUBTextSemanticHint.pageBreakAfter.rawValue)
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stop.pointee = true
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return
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}
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}
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return boundary
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}
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/// 查找附件边界：只有块级附件才触发分页。
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func preferredAttachmentBoundary(
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in range: NSRange,
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minimumEnd: Int,
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factory: RDEPUBCoreTextPageFrameFactory
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) -> Int? {
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guard let safeRange = factory.clampedRange(range), safeRange.length > 0 else {
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return nil
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}
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var boundary: Int?
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attributedString.enumerateAttribute(.rdPageAttachmentKind, in: safeRange) { value, attributeRange, stop in
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guard value != nil else { return }
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let location = attributeRange.location
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let placement = factory.attachmentPlacement(at: location)
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let blockKind = factory.blockKind(at: location)
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let isBlockLevelAttachment: Bool
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switch placement {
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case .centered:
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isBlockLevelAttachment = true
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case .inline, .baseline:
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isBlockLevelAttachment = false
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case nil:
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isBlockLevelAttachment = blockKind == .attachment
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}
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guard isBlockLevelAttachment else { return }
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let boundaryRange = factory.blockRange(at: location) ?? factory.paragraphRange(containing: location)
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if boundaryRange.location > safeRange.location, boundaryRange.location >= minimumEnd {
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boundary = boundaryRange.location
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stop.pointee = true
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}
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}
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return boundary
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}
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/// 查找 pageRelate 跨页关联边界。
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func preferredPageRelateBoundary(
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after range: NSRange,
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minimumEnd: Int,
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lineRanges: [NSRange],
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factory: RDEPUBCoreTextPageFrameFactory
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) -> Int? {
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let pageStartOfNext = range.location + range.length
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guard pageStartOfNext > range.location,
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pageStartOfNext < attributedString.length,
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lineRanges.count >= 2,
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factory.semanticHints(at: pageStartOfNext).contains(.pageRelate) else {
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return nil
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}
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let boundaryBlockStart = factory.blockRange(at: pageStartOfNext)?.location
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?? factory.paragraphRange(containing: pageStartOfNext).location
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guard boundaryBlockStart == pageStartOfNext else { return nil }
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let lastLineStart = lineRanges[lineRanges.count - 1].location
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guard lastLineStart > range.location, lastLineStart >= minimumEnd else {
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return nil
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}
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return lastLineStart
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}
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// MARK: - 内部工具
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private func shouldTreatAvoidHintAsBlockProtection(_ attributes: [NSAttributedString.Key: Any]) -> Bool {
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guard let rawValue = attributes[.rdPageSemanticHints] as? String else {
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return false
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}
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let hints = rawValue
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.split(separator: ",")
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.compactMap { RDEPUBTextSemanticHint(rawValue: String($0)) }
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guard hints.contains(.avoidPageBreakInside) else {
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return false
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}
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let placement = (attributes[.rdPageAttachmentPlacement] as? String)
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.flatMap(RDEPUBTextAttachmentPlacement.init(rawValue:))
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let blockKind = (attributes[.rdPageBlockKind] as? String)
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.flatMap(RDEPUBTextBlockKind.init(rawValue:))
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if blockKind == .attachment, placement != .centered {
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return false
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}
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return true
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}
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private func clampedProbeRange(for lineRange: NSRange) -> NSRange? {
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clampedRange(NSRange(location: lineRange.location, length: max(lineRange.length, 1)))
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}
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private func clampedRange(_ range: NSRange) -> NSRange? {
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guard range.location >= 0, range.length >= 0 else { return nil }
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guard attributedString.length > 0 else {
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return range.location == 0 ? NSRange(location: 0, length: 0) : nil
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}
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guard range.location < attributedString.length else { return nil }
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let maxLength = attributedString.length - range.location
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return NSRange(location: range.location, length: min(range.length, maxLength))
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}
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}
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