558 lines
23 KiB
C++
558 lines
23 KiB
C++
#include "ParsedText.h"
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#include <GfxRenderer.h>
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#include <Utf8.h>
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#include <algorithm>
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#include <cmath>
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#include <functional>
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#include <limits>
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#include <vector>
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#include "hyphenation/Hyphenator.h"
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constexpr int MAX_COST = std::numeric_limits<int>::max();
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namespace {
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// Soft hyphen byte pattern used throughout EPUBs (UTF-8 for U+00AD).
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constexpr char SOFT_HYPHEN_UTF8[] = "\xC2\xAD";
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constexpr size_t SOFT_HYPHEN_BYTES = 2;
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// Returns the first rendered codepoint of a word (skipping leading soft hyphens).
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uint32_t firstCodepoint(const std::string& word) {
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const auto* ptr = reinterpret_cast<const unsigned char*>(word.c_str());
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while (true) {
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const uint32_t cp = utf8NextCodepoint(&ptr);
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if (cp == 0) return 0;
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if (cp != 0x00AD) return cp; // skip soft hyphens
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}
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}
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// Returns the last codepoint of a word by scanning backward for the start of the last UTF-8 sequence.
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uint32_t lastCodepoint(const std::string& word) {
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if (word.empty()) return 0;
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// UTF-8 continuation bytes start with 10xxxxxx; scan backward to find the leading byte.
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size_t i = word.size() - 1;
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while (i > 0 && (static_cast<uint8_t>(word[i]) & 0xC0) == 0x80) {
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--i;
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}
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const auto* ptr = reinterpret_cast<const unsigned char*>(word.c_str() + i);
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return utf8NextCodepoint(&ptr);
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}
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bool containsSoftHyphen(const std::string& word) { return word.find(SOFT_HYPHEN_UTF8) != std::string::npos; }
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// Removes every soft hyphen in-place so rendered glyphs match measured widths.
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void stripSoftHyphensInPlace(std::string& word) {
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size_t pos = 0;
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while ((pos = word.find(SOFT_HYPHEN_UTF8, pos)) != std::string::npos) {
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word.erase(pos, SOFT_HYPHEN_BYTES);
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}
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}
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// Returns the advance width for a word while ignoring soft hyphen glyphs and optionally appending a visible hyphen.
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// Uses advance width (sum of glyph advances + kerning) rather than bounding box width so that italic glyph overhangs
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// don't inflate inter-word spacing.
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uint16_t measureWordWidth(const GfxRenderer& renderer, const int fontId, const std::string& word,
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const EpdFontFamily::Style style, const bool appendHyphen = false) {
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if (word.size() == 1 && word[0] == ' ' && !appendHyphen) {
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return renderer.getSpaceWidth(fontId, style);
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}
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const bool hasSoftHyphen = containsSoftHyphen(word);
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if (!hasSoftHyphen && !appendHyphen) {
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return renderer.getTextAdvanceX(fontId, word.c_str(), style);
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}
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std::string sanitized = word;
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if (hasSoftHyphen) {
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stripSoftHyphensInPlace(sanitized);
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}
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if (appendHyphen) {
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sanitized.push_back('-');
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}
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return renderer.getTextAdvanceX(fontId, sanitized.c_str(), style);
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}
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} // namespace
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void ParsedText::addWord(std::string word, const EpdFontFamily::Style fontStyle, const bool underline,
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const bool attachToPrevious) {
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if (word.empty()) return;
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words.push_back(std::move(word));
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EpdFontFamily::Style combinedStyle = fontStyle;
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if (underline) {
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combinedStyle = static_cast<EpdFontFamily::Style>(combinedStyle | EpdFontFamily::UNDERLINE);
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}
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wordStyles.push_back(combinedStyle);
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wordContinues.push_back(attachToPrevious);
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}
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// Consumes data to minimize memory usage
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void ParsedText::layoutAndExtractLines(const GfxRenderer& renderer, const int fontId, const uint16_t viewportWidth,
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const std::function<void(std::shared_ptr<TextBlock>)>& processLine,
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const bool includeLastLine) {
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if (words.empty()) {
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return;
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}
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// Apply fixed transforms before any per-line layout work.
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applyParagraphIndent();
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const int pageWidth = viewportWidth;
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auto wordWidths = calculateWordWidths(renderer, fontId);
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std::vector<size_t> lineBreakIndices;
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if (hyphenationEnabled) {
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// Use greedy layout that can split words mid-loop when a hyphenated prefix fits.
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lineBreakIndices = computeHyphenatedLineBreaks(renderer, fontId, pageWidth, wordWidths, wordContinues);
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} else {
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lineBreakIndices = computeLineBreaks(renderer, fontId, pageWidth, wordWidths, wordContinues);
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}
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const size_t lineCount = includeLastLine ? lineBreakIndices.size() : lineBreakIndices.size() - 1;
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for (size_t i = 0; i < lineCount; ++i) {
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extractLine(i, pageWidth, wordWidths, wordContinues, lineBreakIndices, processLine, renderer, fontId);
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}
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// Remove consumed words so size() reflects only remaining words
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if (lineCount > 0) {
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const size_t consumed = lineBreakIndices[lineCount - 1];
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words.erase(words.begin(), words.begin() + consumed);
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wordStyles.erase(wordStyles.begin(), wordStyles.begin() + consumed);
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wordContinues.erase(wordContinues.begin(), wordContinues.begin() + consumed);
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}
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}
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std::vector<uint16_t> ParsedText::calculateWordWidths(const GfxRenderer& renderer, const int fontId) {
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std::vector<uint16_t> wordWidths;
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wordWidths.reserve(words.size());
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for (size_t i = 0; i < words.size(); ++i) {
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wordWidths.push_back(measureWordWidth(renderer, fontId, words[i], wordStyles[i]));
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}
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return wordWidths;
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}
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std::vector<size_t> ParsedText::computeLineBreaks(const GfxRenderer& renderer, const int fontId, const int pageWidth,
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std::vector<uint16_t>& wordWidths, std::vector<bool>& continuesVec) {
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if (words.empty()) {
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return {};
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}
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// Calculate first line indent (only for left/justified text).
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// Positive text-indent (paragraph indent) is suppressed when extraParagraphSpacing is on.
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// Negative text-indent (hanging indent, e.g. margin-left:3em; text-indent:-1em) always applies —
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// it is structural (positions the bullet/marker), not decorative.
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const int firstLineIndent =
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blockStyle.textIndentDefined && (blockStyle.textIndent < 0 || !extraParagraphSpacing) &&
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(blockStyle.alignment == CssTextAlign::Justify || blockStyle.alignment == CssTextAlign::Left)
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? blockStyle.textIndent
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: 0;
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// Ensure any word that would overflow even as the first entry on a line is split using fallback hyphenation.
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for (size_t i = 0; i < wordWidths.size(); ++i) {
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// First word needs to fit in reduced width if there's an indent
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const int effectiveWidth = i == 0 ? pageWidth - firstLineIndent : pageWidth;
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while (wordWidths[i] > effectiveWidth) {
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if (!hyphenateWordAtIndex(i, effectiveWidth, renderer, fontId, wordWidths, /*allowFallbackBreaks=*/true)) {
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break;
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}
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}
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}
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const size_t totalWordCount = words.size();
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// Pre-compute inter-word gaps once so the O(n²) DP inner loop avoids repeated
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// codepoint scanning and renderer calls for every (i,j) pair.
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// interWordGaps[j] = the spacing between words[j-1] and words[j] (0 for j==0).
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std::vector<int> interWordGaps(totalWordCount, 0);
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for (size_t j = 1; j < totalWordCount; ++j) {
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if (!continuesVec[j]) {
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interWordGaps[j] =
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renderer.getSpaceAdvance(fontId, lastCodepoint(words[j - 1]), firstCodepoint(words[j]), wordStyles[j - 1]);
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} else {
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interWordGaps[j] =
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renderer.getKerning(fontId, lastCodepoint(words[j - 1]), firstCodepoint(words[j]), wordStyles[j - 1]);
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}
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}
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// DP table to store the minimum badness (cost) of lines starting at index i
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std::vector<int> dp(totalWordCount);
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// 'ans[i]' stores the index 'j' of the *last word* in the optimal line starting at 'i'
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std::vector<size_t> ans(totalWordCount);
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// Base Case
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dp[totalWordCount - 1] = 0;
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ans[totalWordCount - 1] = totalWordCount - 1;
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for (int i = totalWordCount - 2; i >= 0; --i) {
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int currlen = 0;
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dp[i] = MAX_COST;
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// First line has reduced width due to text-indent
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const int effectivePageWidth = i == 0 ? pageWidth - firstLineIndent : pageWidth;
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for (size_t j = i; j < totalWordCount; ++j) {
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const int gap = (j > static_cast<size_t>(i)) ? interWordGaps[j] : 0;
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currlen += wordWidths[j] + gap;
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if (currlen > effectivePageWidth) {
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break;
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}
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// Cannot break after word j if the next word attaches to it (continuation group)
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if (j + 1 < totalWordCount && continuesVec[j + 1]) {
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continue;
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}
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int cost;
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if (j == totalWordCount - 1) {
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cost = 0; // Last line
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} else {
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const int remainingSpace = effectivePageWidth - currlen;
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// Use long long for the square to prevent overflow
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const long long cost_ll = static_cast<long long>(remainingSpace) * remainingSpace + dp[j + 1];
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if (cost_ll > MAX_COST) {
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cost = MAX_COST;
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} else {
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cost = static_cast<int>(cost_ll);
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}
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}
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if (cost < dp[i]) {
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dp[i] = cost;
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ans[i] = j; // j is the index of the last word in this optimal line
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}
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}
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// Handle oversized word: if no valid configuration found, force single-word line
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// This prevents cascade failure where one oversized word breaks all preceding words
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if (dp[i] == MAX_COST) {
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ans[i] = i; // Just this word on its own line
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// Inherit cost from next word to allow subsequent words to find valid configurations
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if (i + 1 < static_cast<int>(totalWordCount)) {
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dp[i] = dp[i + 1];
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} else {
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dp[i] = 0;
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}
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}
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}
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// Stores the index of the word that starts the next line (last_word_index + 1)
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std::vector<size_t> lineBreakIndices;
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size_t currentWordIndex = 0;
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while (currentWordIndex < totalWordCount) {
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size_t nextBreakIndex = ans[currentWordIndex] + 1;
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// Safety check: prevent infinite loop if nextBreakIndex doesn't advance
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if (nextBreakIndex <= currentWordIndex) {
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// Force advance by at least one word to avoid infinite loop
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nextBreakIndex = currentWordIndex + 1;
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}
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lineBreakIndices.push_back(nextBreakIndex);
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currentWordIndex = nextBreakIndex;
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}
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return lineBreakIndices;
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}
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void ParsedText::applyParagraphIndent() {
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if (extraParagraphSpacing || words.empty()) {
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return;
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}
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if (blockStyle.textIndentDefined) {
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// CSS text-indent is explicitly set (even if 0) - don't use fallback EmSpace
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// The actual indent positioning is handled in extractLine()
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} else if (blockStyle.alignment == CssTextAlign::Justify || blockStyle.alignment == CssTextAlign::Left) {
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// No CSS text-indent defined - use EmSpace fallback for visual indent
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words.front().insert(0, "\xe2\x80\x83");
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}
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}
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// Builds break indices while opportunistically splitting the word that would overflow the current line.
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std::vector<size_t> ParsedText::computeHyphenatedLineBreaks(const GfxRenderer& renderer, const int fontId,
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const int pageWidth, std::vector<uint16_t>& wordWidths,
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std::vector<bool>& continuesVec) {
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// Calculate first line indent (only for left/justified text).
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// Positive text-indent (paragraph indent) is suppressed when extraParagraphSpacing is on.
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// Negative text-indent (hanging indent, e.g. margin-left:3em; text-indent:-1em) always applies —
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// it is structural (positions the bullet/marker), not decorative.
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const int firstLineIndent =
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blockStyle.textIndentDefined && (blockStyle.textIndent < 0 || !extraParagraphSpacing) &&
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(blockStyle.alignment == CssTextAlign::Justify || blockStyle.alignment == CssTextAlign::Left)
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? blockStyle.textIndent
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: 0;
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// Pre-compute inter-word gaps to avoid repeated codepoint scanning and renderer
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// calls in the inner loop. When hyphenateWordAtIndex inserts a new word, we insert
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// a placeholder gap (0) at that position to keep the vector in sync; the remainder
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// is always the first word on the next line so its spacing is never used.
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std::vector<int> interWordGaps(wordWidths.size(), 0);
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for (size_t j = 1; j < wordWidths.size(); ++j) {
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if (!continuesVec[j]) {
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interWordGaps[j] =
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renderer.getSpaceAdvance(fontId, lastCodepoint(words[j - 1]), firstCodepoint(words[j]), wordStyles[j - 1]);
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} else {
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interWordGaps[j] =
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renderer.getKerning(fontId, lastCodepoint(words[j - 1]), firstCodepoint(words[j]), wordStyles[j - 1]);
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}
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}
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std::vector<size_t> lineBreakIndices;
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size_t currentIndex = 0;
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bool isFirstLine = true;
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while (currentIndex < wordWidths.size()) {
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const size_t lineStart = currentIndex;
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int lineWidth = 0;
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// First line has reduced width due to text-indent
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const int effectivePageWidth = isFirstLine ? pageWidth - firstLineIndent : pageWidth;
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// Consume as many words as possible for current line, splitting when prefixes fit
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while (currentIndex < wordWidths.size()) {
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const bool isFirstWord = currentIndex == lineStart;
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const int spacing = isFirstWord ? 0 : interWordGaps[currentIndex];
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const int candidateWidth = spacing + wordWidths[currentIndex];
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// Word fits on current line
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if (lineWidth + candidateWidth <= effectivePageWidth) {
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lineWidth += candidateWidth;
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++currentIndex;
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continue;
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}
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// Word would overflow — try to split based on hyphenation points
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const int availableWidth = effectivePageWidth - lineWidth - spacing;
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const bool allowFallbackBreaks = isFirstWord; // Only for first word on line
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if (availableWidth > 0 &&
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hyphenateWordAtIndex(currentIndex, availableWidth, renderer, fontId, wordWidths, allowFallbackBreaks)) {
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// Keep interWordGaps in sync: insert placeholder for the new remainder word.
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// The remainder is always the first word on the next line so this slot is never read.
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interWordGaps.insert(interWordGaps.begin() + currentIndex + 1, 0);
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// Prefix now fits; append it to this line and move to next line
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lineWidth += spacing + wordWidths[currentIndex];
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++currentIndex;
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break;
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}
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// Could not split: force at least one word per line to avoid infinite loop
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if (currentIndex == lineStart) {
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lineWidth += candidateWidth;
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++currentIndex;
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}
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break;
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}
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// Don't break before a continuation word (e.g., orphaned "?" after "question").
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// Backtrack to the start of the continuation group so the whole group moves to the next line.
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while (currentIndex > lineStart + 1 && currentIndex < wordWidths.size() && continuesVec[currentIndex]) {
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--currentIndex;
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}
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lineBreakIndices.push_back(currentIndex);
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isFirstLine = false;
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}
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return lineBreakIndices;
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}
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// Splits words[wordIndex] into prefix (adding a hyphen only when needed) and remainder when a legal breakpoint fits the
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// available width.
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bool ParsedText::hyphenateWordAtIndex(const size_t wordIndex, const int availableWidth, const GfxRenderer& renderer,
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const int fontId, std::vector<uint16_t>& wordWidths,
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const bool allowFallbackBreaks) {
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// Guard against invalid indices or zero available width before attempting to split.
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if (availableWidth <= 0 || wordIndex >= words.size()) {
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return false;
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}
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const std::string& word = words[wordIndex];
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const auto style = wordStyles[wordIndex];
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// Collect candidate breakpoints (byte offsets and hyphen requirements).
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auto breakInfos = Hyphenator::breakOffsets(word, allowFallbackBreaks);
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if (breakInfos.empty()) {
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return false;
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}
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size_t chosenOffset = 0;
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int chosenWidth = -1;
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bool chosenNeedsHyphen = true;
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// Iterate over each legal breakpoint and retain the widest prefix that still fits.
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for (const auto& info : breakInfos) {
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const size_t offset = info.byteOffset;
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if (offset == 0 || offset >= word.size()) {
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continue;
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}
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const bool needsHyphen = info.requiresInsertedHyphen;
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const int prefixWidth = measureWordWidth(renderer, fontId, word.substr(0, offset), style, needsHyphen);
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if (prefixWidth > availableWidth || prefixWidth <= chosenWidth) {
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continue; // Skip if too wide or not an improvement
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}
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chosenWidth = prefixWidth;
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chosenOffset = offset;
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chosenNeedsHyphen = needsHyphen;
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}
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if (chosenWidth < 0) {
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// No hyphenation point produced a prefix that fits in the remaining space.
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return false;
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}
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// Split the word at the selected breakpoint and append a hyphen if required.
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std::string remainder = word.substr(chosenOffset);
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words[wordIndex].resize(chosenOffset);
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if (chosenNeedsHyphen) {
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words[wordIndex].push_back('-');
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}
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// Insert the remainder word (with matching style and continuation flag) directly after the prefix.
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words.insert(words.begin() + wordIndex + 1, remainder);
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wordStyles.insert(wordStyles.begin() + wordIndex + 1, style);
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// Continuation flag handling after splitting a word into prefix + remainder.
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//
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// The prefix keeps the original word's continuation flag so that no-break-space groups
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// stay linked. The remainder always gets continues=false because it starts on the next
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// line and is not attached to the prefix.
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//
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// Example: "200 Quadratkilometer" produces tokens:
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// [0] "200" continues=false
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// [1] " " continues=true
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// [2] "Quadratkilometer" continues=true <-- the word being split
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//
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// After splitting "Quadratkilometer" at "Quadrat-" / "kilometer":
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// [0] "200" continues=false
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// [1] " " continues=true
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// [2] "Quadrat-" continues=true (KEPT — still attached to the no-break group)
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// [3] "kilometer" continues=false (NEW — starts fresh on the next line)
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//
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// This lets the backtracking loop keep the entire prefix group ("200 Quadrat-") on one
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// line, while "kilometer" moves to the next line.
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// wordContinues[wordIndex] is intentionally left unchanged — the prefix keeps its original attachment.
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wordContinues.insert(wordContinues.begin() + wordIndex + 1, false);
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// Update cached widths to reflect the new prefix/remainder pairing.
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wordWidths[wordIndex] = static_cast<uint16_t>(chosenWidth);
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const uint16_t remainderWidth = measureWordWidth(renderer, fontId, remainder, style);
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wordWidths.insert(wordWidths.begin() + wordIndex + 1, remainderWidth);
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return true;
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}
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void ParsedText::extractLine(const size_t breakIndex, const int pageWidth, const std::vector<uint16_t>& wordWidths,
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const std::vector<bool>& continuesVec, const std::vector<size_t>& lineBreakIndices,
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const std::function<void(std::shared_ptr<TextBlock>)>& processLine,
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const GfxRenderer& renderer, const int fontId) {
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const size_t lineBreak = lineBreakIndices[breakIndex];
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const size_t lastBreakAt = breakIndex > 0 ? lineBreakIndices[breakIndex - 1] : 0;
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const size_t lineWordCount = lineBreak - lastBreakAt;
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// Calculate first line indent (only for left/justified text).
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// Positive text-indent (paragraph indent) is suppressed when extraParagraphSpacing is on.
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// Negative text-indent (hanging indent, e.g. margin-left:3em; text-indent:-1em) always applies —
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// it is structural (positions the bullet/marker), not decorative.
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const bool isFirstLine = breakIndex == 0;
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const int firstLineIndent =
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isFirstLine && blockStyle.textIndentDefined && (blockStyle.textIndent < 0 || !extraParagraphSpacing) &&
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(blockStyle.alignment == CssTextAlign::Justify || blockStyle.alignment == CssTextAlign::Left)
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? blockStyle.textIndent
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: 0;
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// Calculate total word width for this line, count actual word gaps,
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// and accumulate total natural gap widths (including space kerning adjustments).
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int lineWordWidthSum = 0;
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size_t actualGapCount = 0;
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int totalNaturalGaps = 0;
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for (size_t wordIdx = 0; wordIdx < lineWordCount; wordIdx++) {
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lineWordWidthSum += wordWidths[lastBreakAt + wordIdx];
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// Count gaps: each word after the first creates a gap, unless it's a continuation
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if (wordIdx > 0 && !continuesVec[lastBreakAt + wordIdx]) {
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actualGapCount++;
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totalNaturalGaps +=
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renderer.getSpaceAdvance(fontId, lastCodepoint(words[lastBreakAt + wordIdx - 1]),
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firstCodepoint(words[lastBreakAt + wordIdx]), wordStyles[lastBreakAt + wordIdx - 1]);
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} else if (wordIdx > 0 && continuesVec[lastBreakAt + wordIdx]) {
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// Cross-boundary kerning for continuation words (e.g. nonbreaking spaces, attached punctuation)
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totalNaturalGaps +=
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renderer.getKerning(fontId, lastCodepoint(words[lastBreakAt + wordIdx - 1]),
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firstCodepoint(words[lastBreakAt + wordIdx]), wordStyles[lastBreakAt + wordIdx - 1]);
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}
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}
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// Calculate spacing (account for indent reducing effective page width on first line)
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const int effectivePageWidth = pageWidth - firstLineIndent;
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const bool isLastLine = breakIndex == lineBreakIndices.size() - 1;
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// For justified text, compute per-gap extra to distribute remaining space evenly
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const int spareSpace = effectivePageWidth - lineWordWidthSum - totalNaturalGaps;
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const int justifyExtra = (blockStyle.alignment == CssTextAlign::Justify && !isLastLine && actualGapCount >= 1)
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? spareSpace / static_cast<int>(actualGapCount)
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: 0;
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// Calculate initial x position (first line starts at indent for left/justified text;
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// may be negative for hanging indents, e.g. margin-left:3em; text-indent:-1em).
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auto xpos = static_cast<int16_t>(firstLineIndent);
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if (blockStyle.alignment == CssTextAlign::Right) {
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xpos = effectivePageWidth - lineWordWidthSum - totalNaturalGaps;
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} else if (blockStyle.alignment == CssTextAlign::Center) {
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xpos = (effectivePageWidth - lineWordWidthSum - totalNaturalGaps) / 2;
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}
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// Pre-calculate X positions for words
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// Continuation words attach to the previous word with no space before them
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std::vector<int16_t> lineXPos;
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lineXPos.reserve(lineWordCount);
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for (size_t wordIdx = 0; wordIdx < lineWordCount; wordIdx++) {
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lineXPos.push_back(xpos);
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const bool nextIsContinuation = wordIdx + 1 < lineWordCount && continuesVec[lastBreakAt + wordIdx + 1];
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if (nextIsContinuation) {
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int advance = wordWidths[lastBreakAt + wordIdx];
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// Cross-boundary kerning for continuation words (e.g. nonbreaking spaces, attached punctuation)
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advance +=
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renderer.getKerning(fontId, lastCodepoint(words[lastBreakAt + wordIdx]),
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firstCodepoint(words[lastBreakAt + wordIdx + 1]), wordStyles[lastBreakAt + wordIdx]);
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xpos += advance;
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} else {
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int gap = 0;
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if (wordIdx + 1 < lineWordCount) {
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gap = renderer.getSpaceAdvance(fontId, lastCodepoint(words[lastBreakAt + wordIdx]),
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firstCodepoint(words[lastBreakAt + wordIdx + 1]),
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wordStyles[lastBreakAt + wordIdx]);
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}
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if (blockStyle.alignment == CssTextAlign::Justify && !isLastLine) {
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gap += justifyExtra;
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}
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xpos += wordWidths[lastBreakAt + wordIdx] + gap;
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}
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}
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// Build line data by moving from the original vectors using index range
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std::vector<std::string> lineWords(std::make_move_iterator(words.begin() + lastBreakAt),
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std::make_move_iterator(words.begin() + lineBreak));
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std::vector<EpdFontFamily::Style> lineWordStyles(wordStyles.begin() + lastBreakAt, wordStyles.begin() + lineBreak);
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for (auto& word : lineWords) {
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if (containsSoftHyphen(word)) {
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stripSoftHyphensInPlace(word);
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}
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}
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processLine(
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std::make_shared<TextBlock>(std::move(lineWords), std::move(lineXPos), std::move(lineWordStyles), blockStyle));
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}
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