chore: checkpoint current milestone work
This commit is contained in:
shen
@@ -0,0 +1,244 @@
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import CoreText
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import UIKit
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struct RDEPUBTextLayouter {
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private let attributedString: NSAttributedString
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private let pageSize: CGSize
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private let framesetter: CTFramesetter
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private let path: CGPath
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init(attributedString: NSAttributedString, pageSize: CGSize) {
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self.attributedString = attributedString
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self.pageSize = pageSize
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self.framesetter = CTFramesetterCreateWithAttributedString(attributedString)
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self.path = CGPath(rect: CGRect(origin: .zero, size: pageSize), transform: nil)
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}
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func layoutFrames(fragmentOffsets: [String: Int] = [:]) -> [RDEPUBTextLayoutFrame] {
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guard attributedString.length > 0, pageSize.width > 0, pageSize.height > 0 else {
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return []
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}
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var frames: [RDEPUBTextLayoutFrame] = []
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var location = 0
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while location < attributedString.length {
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let frame = CTFramesetterCreateFrame(framesetter, CFRangeMake(location, 0), path, nil)
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let visibleRange = CTFrameGetVisibleStringRange(frame)
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guard visibleRange.length > 0 else {
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break
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}
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let proposedRange = NSRange(location: location, length: visibleRange.length)
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let adjusted = adjustedRange(from: proposedRange, totalLength: attributedString.length)
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let trailingFragmentID = nearestTrailingFragmentID(
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endingAt: adjusted.range.location + adjusted.range.length,
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fragmentOffsets: fragmentOffsets
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)
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frames.append(
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RDEPUBTextLayoutFrame(
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contentRange: adjusted.range,
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breakReason: adjusted.breakReason,
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blockRange: adjusted.blockRange,
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attachmentRanges: adjusted.attachmentRanges,
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attachmentKinds: adjusted.attachmentKinds,
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trailingFragmentID: trailingFragmentID,
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diagnostics: adjusted.diagnostics
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)
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)
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let nextLocation = adjusted.range.location + adjusted.range.length
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guard nextLocation > location else {
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location += max(visibleRange.length, 1)
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continue
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}
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location = nextLocation
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}
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return frames
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}
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private func adjustedRange(
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from proposedRange: NSRange,
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totalLength: Int
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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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diagnostics: [String]
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) {
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let pageEnd = proposedRange.location + proposedRange.length
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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: blockRange(at: max(proposedRange.location, pageEnd - 1)),
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attachmentRanges: attachmentRanges(in: proposedRange),
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attachmentKinds: attachmentKinds(in: proposedRange),
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diagnostics: diagnostics(
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reason: .chapterEnd,
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range: proposedRange,
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attachmentRanges: attachmentRanges(in: proposedRange),
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blockRange: blockRange(at: max(proposedRange.location, pageEnd - 1))
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)
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)
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}
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let minLength = max(Int(Double(proposedRange.length) * 0.55), 1)
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let minimumEnd = proposedRange.location + minLength
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let currentBlockRange = blockRange(at: max(proposedRange.location, pageEnd - 1))
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let currentAttachmentRanges = attachmentRanges(in: proposedRange)
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let currentAttachmentKinds = attachmentKinds(in: proposedRange)
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if let attachmentBoundary = preferredAttachmentBoundary(
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in: proposedRange,
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minimumEnd: minimumEnd
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) {
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let adjustedRange = NSRange(location: proposedRange.location, length: attachmentBoundary - proposedRange.location)
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return (
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range: adjustedRange,
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breakReason: .attachmentBoundary,
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blockRange: currentBlockRange,
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attachmentRanges: currentAttachmentRanges,
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attachmentKinds: currentAttachmentKinds,
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diagnostics: diagnostics(
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reason: .attachmentBoundary,
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range: adjustedRange,
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attachmentRanges: currentAttachmentRanges,
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blockRange: currentBlockRange
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)
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)
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}
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if let blockBoundary = preferredBlockBoundary(
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near: pageEnd,
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lowerBound: minimumEnd
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) {
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let adjustedRange = NSRange(location: proposedRange.location, length: blockBoundary - proposedRange.location)
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return (
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range: adjustedRange,
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breakReason: .blockBoundary,
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blockRange: currentBlockRange,
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attachmentRanges: currentAttachmentRanges,
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attachmentKinds: currentAttachmentKinds,
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diagnostics: diagnostics(
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reason: .blockBoundary,
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range: adjustedRange,
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attachmentRanges: currentAttachmentRanges,
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blockRange: currentBlockRange
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)
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)
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}
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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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diagnostics: 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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)
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)
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}
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private func preferredAttachmentBoundary(in range: NSRange, minimumEnd: Int) -> Int? {
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var boundary: Int?
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attributedString.enumerateAttribute(.rdPageAttachmentKind, in: range) { value, attributeRange, stop in
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guard value != nil else { return }
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let paragraphRange = paragraphRange(containing: attributeRange.location)
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if paragraphRange.location > range.location, paragraphRange.location >= minimumEnd {
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boundary = paragraphRange.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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private func preferredBlockBoundary(near location: Int, lowerBound: Int) -> Int? {
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var probe = max(lowerBound, 0)
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let searchEnd = min(location, attributedString.length)
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guard probe < searchEnd else { return nil }
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var lastBoundary: Int?
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while probe < searchEnd {
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let block = blockRange(at: probe) ?? paragraphRange(containing: probe)
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let candidate = block.location
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if candidate > lowerBound, candidate < location {
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lastBoundary = candidate
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}
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probe = max(block.location + max(block.length, 1), probe + 1)
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}
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return lastBoundary
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}
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private func blockRange(at location: Int) -> NSRange? {
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guard location >= 0, location < attributedString.length else { return nil }
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let attributes = attributedString.attributes(at: location, effectiveRange: nil)
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if let encodedRange = attributes[.rdPageBlockRange] as? String {
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return NSRangeFromString(encodedRange)
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}
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return nil
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}
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private func paragraphRange(containing location: Int) -> NSRange {
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let source = attributedString.string as NSString
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guard source.length > 0 else { return NSRange(location: 0, length: 0) }
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let safeLocation = min(max(location, 0), max(source.length - 1, 0))
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return source.paragraphRange(for: NSRange(location: safeLocation, length: 0))
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}
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private func attachmentRanges(in range: NSRange) -> [NSRange] {
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var results: [NSRange] = []
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attributedString.enumerateAttribute(.rdPageAttachmentKind, in: range) { value, attributeRange, _ in
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guard value != nil else { return }
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results.append(attributeRange)
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}
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return results
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}
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private func attachmentKinds(in range: NSRange) -> [RDEPUBTextAttachmentKind] {
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var kinds: [RDEPUBTextAttachmentKind] = []
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attributedString.enumerateAttribute(.rdPageAttachmentKind, in: range) { value, _, _ in
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guard let rawValue = value as? String,
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let kind = RDEPUBTextAttachmentKind(rawValue: rawValue),
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!kinds.contains(kind) else {
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return
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}
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kinds.append(kind)
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}
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return kinds
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}
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private func nearestTrailingFragmentID(
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endingAt location: Int,
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fragmentOffsets: [String: Int]
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) -> String? {
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fragmentOffsets
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.filter { $0.value <= location }
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.max { lhs, rhs in lhs.value < rhs.value }?
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.key
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}
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private func diagnostics(
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reason: RDEPUBTextPageBreakReason,
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range: NSRange,
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attachmentRanges: [NSRange],
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blockRange: NSRange?
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) -> [String] {
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var items = ["page break: \(reason.rawValue)", "page range: \(NSStringFromRange(range))"]
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if let blockRange {
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items.append("block range: \(NSStringFromRange(blockRange))")
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}
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if !attachmentRanges.isEmpty {
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items.append("attachment ranges: \(attachmentRanges.map(NSStringFromRange).joined(separator: ","))")
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}
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return items
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}
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}
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