140 lines
5.9 KiB
Swift
140 lines
5.9 KiB
Swift
import UIKit
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#if canImport(DTCoreText)
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import DTCoreText
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#endif
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/// DTCoreText 渲染器实现：将 EPUB 章节 HTML 转换为富文本（NSAttributedString）。
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///
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/// 这是 `RDEPUBTextRenderer` 协议的默认实现，位于渲染链路的第二步：
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/// 章节 HTML → DTCoreText 渲染 → NSAttributedString → 提取 fragment 偏移量 → 统一字体/行距
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///
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/// DTCoreText 库负责将 HTML 解析为带有排版属性的富文本，
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/// 渲染过程中会通过 `willFlushCallback` 回调对每个 DOM 元素做布局规范化（图片尺寸等）。
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/// 当 DTCoreText 不可用时（条件编译失败），回退到纯文本渲染。
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public struct RDEPUBDTCoreTextRenderer: RDEPUBTextRenderer {
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public init() {}
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/// DTCoreText 库是否在当前编译环境中可用
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public static var isAvailable: Bool {
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#if canImport(DTCoreText)
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return true
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#else
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return false
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#endif
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}
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/// 渲染单个章节：HTML → NSAttributedString，同时提取 fragment 和语义标记。
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public func renderChapter(
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request: RDEPUBTextChapterRenderRequest
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) throws -> RDEPUBRenderedChapterContent {
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#if canImport(DTCoreText)
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let chapterContext = request.context
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guard let data = chapterContext.html.data(using: .utf8) else {
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throw RDEPUBTextRenderingError.htmlEncodingFailed
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}
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guard let rendered = makeAttributedString(from: data, request: request) else {
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return fallbackRenderedContent(request: request)
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}
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let attributedString = NSMutableAttributedString(attributedString: rendered)
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RDEPUBSemanticMarkerInjector.applyPaginationSemantics(in: attributedString)
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let fragmentOffsets = RDEPUBFragmentMarkerInjector.extractFragmentOffsets(from: attributedString)
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RDEPUBTextRendererSupport.normalizeReadingAttributes(in: attributedString, style: request.style)
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return RDEPUBRenderedChapterContent(
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attributedString: attributedString,
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fragmentOffsets: fragmentOffsets,
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resourceDiagnostics: chapterContext.resourceDiagnostics
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)
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#else
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return fallbackRenderedContent(request: request)
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#endif
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}
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/// 便捷方法：直接传入 HTML 字符串进行渲染（不含上下文信息）
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public func renderChapter(
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html: String,
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baseURL: URL?,
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style: RDEPUBTextRenderStyle
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) throws -> RDEPUBRenderedChapterContent {
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let request = RDEPUBTextTypesetterPipeline().makeRequest(
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from: RDEPUBTypesettingInput(
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href: "",
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title: "",
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rawHTML: html,
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baseURL: baseURL,
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style: style,
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resourceResolver: nil
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)
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).request
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return try renderChapter(request: request)
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}
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/// 回退渲染：当 DTCoreText 不可用时，将 HTML 源码当作纯文本处理
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private func fallbackRenderedContent(request: RDEPUBTextChapterRenderRequest) -> RDEPUBRenderedChapterContent {
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let attributedString = RDEPUBTextRendererSupport.fallbackAttributedString(for: request.context.html, style: request.style)
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RDEPUBSemanticMarkerInjector.applyPaginationSemantics(in: attributedString)
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let fragmentOffsets = RDEPUBFragmentMarkerInjector.extractFragmentOffsets(from: attributedString)
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RDEPUBTextRendererSupport.normalizeReadingAttributes(in: attributedString, style: request.style)
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return RDEPUBRenderedChapterContent(
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attributedString: attributedString,
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fragmentOffsets: fragmentOffsets,
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resourceDiagnostics: request.context.resourceDiagnostics
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)
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}
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#if canImport(DTCoreText)
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/// 使用 DTCoreText 将 HTML Data 解析为富文本。
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private func makeAttributedString(from data: Data, request: RDEPUBTextChapterRenderRequest) -> NSAttributedString? {
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let builder = DTHTMLAttributedStringBuilder(
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html: data,
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options: dtOptions(request: request),
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documentAttributes: nil
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)
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builder?.willFlushCallback = { element in
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guard let element else { return }
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RDEPUBAttachmentNormalizer.prepareHTMLElementForReaderRendering(
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element,
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style: request.style,
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maxImageSize: resolvedMaxImageSize(for: request)
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)
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}
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return builder?.generatedAttributedString()
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}
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/// 构建 DTCoreText 的解析选项字典，包括字体、行高、图片尺寸限制等。
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private func dtOptions(request: RDEPUBTextChapterRenderRequest) -> [AnyHashable: Any] {
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let style = request.style
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let maxImageSize = resolvedMaxImageSize(for: request)
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var options: [AnyHashable: Any] = [
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NSTextSizeMultiplierDocumentOption: 1.0,
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DTDefaultFontFamily: style.font.familyName,
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DTDefaultFontName: style.font.fontName,
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DTDefaultFontSize: style.font.pointSize,
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DTDefaultLineHeightMultiplier: max((style.font.lineHeight + style.lineSpacing) / max(style.font.lineHeight, 1), 1),
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DTUseiOS6Attributes: true,
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DTMaxImageSize: NSValue(cgSize: maxImageSize)
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]
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if let baseURL = request.context.baseURL {
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options[NSBaseURLDocumentOption] = baseURL
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}
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if let textColor = style.textColor {
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options[DTDefaultTextColor] = textColor
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}
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return options
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}
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private func resolvedMaxImageSize(for request: RDEPUBTextChapterRenderRequest) -> CGSize {
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let layoutConfig = request.layoutConfig ?? .default
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let fallbackPageSize = request.pageSize ?? layoutConfig.fallbackViewportSize
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let contentRect = layoutConfig.contentRect(fallback: fallbackPageSize)
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let maxWidth = max(round(contentRect.width), 1)
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let maxHeight = max(round(contentRect.height * layoutConfig.imageMaxHeightRatio), 1)
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return CGSize(width: maxWidth, height: maxHeight)
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}
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#endif
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}
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