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Avoid hypehnation at page breaks

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This commit is contained in:
jpirnay
2026-04-05 10:47:05 +02:00
parent 1398454ad8
commit 1509af8729
4 changed files with 132 additions and 29 deletions
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lib/Epub/Epub/ParsedText.cpp
+88 -16
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@@ -1,6 +1,7 @@
#include "ParsedText.h"
#include <GfxRenderer.h>
#include <Logging.h>
#include <Utf8.h>
#include <algorithm>
@@ -90,9 +91,10 @@ void ParsedText::addWord(std::string word, const EpdFontFamily::Style fontStyle,
}
// Consumes data to minimize memory usage
void ParsedText::layoutAndExtractLines(const GfxRenderer& renderer, const int fontId, const uint16_t viewportWidth,
const std::function<void(std::shared_ptr<TextBlock>)>& processLine,
const bool includeLastLine) {
void ParsedText::layoutAndExtractLines(
const GfxRenderer& renderer, const int fontId, const uint16_t viewportWidth,
const std::function<LineProcessResult(std::shared_ptr<TextBlock>, bool, bool)>& processLine,
const bool includeLastLine) {
if (words.empty()) {
return;
}
@@ -104,16 +106,57 @@ void ParsedText::layoutAndExtractLines(const GfxRenderer& renderer, const int fo
auto wordWidths = calculateWordWidths(renderer, fontId);
std::vector<size_t> lineBreakIndices;
std::vector<bool> lineEndsWithHyphenatedWord;
std::vector<int> splitPrefixWordIndexes;
std::vector<bool> splitInsertedHyphen;
if (hyphenationEnabled) {
// Use greedy layout that can split words mid-loop when a hyphenated prefix fits.
lineBreakIndices = computeHyphenatedLineBreaks(renderer, fontId, pageWidth, wordWidths, wordContinues);
lineBreakIndices =
computeHyphenatedLineBreaks(renderer, fontId, pageWidth, wordWidths, wordContinues, lineEndsWithHyphenatedWord,
splitPrefixWordIndexes, splitInsertedHyphen);
} else {
lineBreakIndices = computeLineBreaks(renderer, fontId, pageWidth, wordWidths, wordContinues);
lineEndsWithHyphenatedWord.assign(lineBreakIndices.size(), false);
splitPrefixWordIndexes.assign(lineBreakIndices.size(), -1);
splitInsertedHyphen.assign(lineBreakIndices.size(), false);
}
const size_t lineCount = includeLastLine ? lineBreakIndices.size() : lineBreakIndices.size() - 1;
size_t lineCount = includeLastLine ? lineBreakIndices.size() : lineBreakIndices.size() - 1;
for (size_t i = 0; i < lineCount; ++i) {
extractLine(i, pageWidth, wordWidths, wordContinues, lineBreakIndices, processLine, renderer, fontId);
const bool lineEndedWithHyphenation = i < lineEndsWithHyphenatedWord.size() ? lineEndsWithHyphenatedWord[i] : false;
const auto result = extractLine(i, pageWidth, wordWidths, wordContinues, lineBreakIndices, processLine, renderer,
fontId, lineEndedWithHyphenation, false);
if (result == LineProcessResult::RetryWithoutHyphenation && lineEndedWithHyphenation) {
LOG_DBG("PTX", "Line %u requested rerender without hyphenation", static_cast<unsigned>(i));
// Undo the split used to end this line so it can be relaid without hyphenation.
const int splitPrefixIndex = i < splitPrefixWordIndexes.size() ? splitPrefixWordIndexes[i] : -1;
if (splitPrefixIndex >= 0 && static_cast<size_t>(splitPrefixIndex + 1) < words.size()) {
std::string merged = words[splitPrefixIndex];
if (i < splitInsertedHyphen.size() && splitInsertedHyphen[i] && !merged.empty() && merged.back() == '-') {
merged.pop_back();
}
merged += words[splitPrefixIndex + 1];
words[splitPrefixIndex] = std::move(merged);
words.erase(words.begin() + splitPrefixIndex + 1);
wordStyles.erase(wordStyles.begin() + splitPrefixIndex + 1);
wordContinues.erase(wordContinues.begin() + splitPrefixIndex + 1);
}
// Re-layout remaining output without hyphenation for this pass.
wordWidths = calculateWordWidths(renderer, fontId);
lineBreakIndices = computeLineBreaks(renderer, fontId, pageWidth, wordWidths, wordContinues);
lineEndsWithHyphenatedWord.assign(lineBreakIndices.size(), false);
splitPrefixWordIndexes.assign(lineBreakIndices.size(), -1);
splitInsertedHyphen.assign(lineBreakIndices.size(), false);
lineCount = includeLastLine ? lineBreakIndices.size() : lineBreakIndices.size() - 1;
if (i < lineCount) {
LOG_DBG("PTX", "Rerendering line %u with hyphenation suppressed", static_cast<unsigned>(i));
extractLine(i, pageWidth, wordWidths, wordContinues, lineBreakIndices, processLine, renderer, fontId, false,
true);
}
}
}
// Remove consumed words so size() reflects only remaining words
@@ -279,7 +322,10 @@ void ParsedText::applyParagraphIndent() {
// Builds break indices while opportunistically splitting the word that would overflow the current line.
std::vector<size_t> ParsedText::computeHyphenatedLineBreaks(const GfxRenderer& renderer, const int fontId,
const int pageWidth, std::vector<uint16_t>& wordWidths,
std::vector<bool>& continuesVec) {
std::vector<bool>& continuesVec,
std::vector<bool>& lineEndsWithHyphenatedWord,
std::vector<int>& splitPrefixWordIndexes,
std::vector<bool>& splitInsertedHyphen) {
// Calculate first line indent (only for left/justified text).
// Positive text-indent (paragraph indent) is suppressed when extraParagraphSpacing is on.
// Negative text-indent (hanging indent, e.g. margin-left:3em; text-indent:-1em) always applies —
@@ -306,12 +352,18 @@ std::vector<size_t> ParsedText::computeHyphenatedLineBreaks(const GfxRenderer& r
}
std::vector<size_t> lineBreakIndices;
lineEndsWithHyphenatedWord.clear();
splitPrefixWordIndexes.clear();
splitInsertedHyphen.clear();
size_t currentIndex = 0;
bool isFirstLine = true;
while (currentIndex < wordWidths.size()) {
const size_t lineStart = currentIndex;
int lineWidth = 0;
bool lineEndedWithHyphenation = false;
int splitPrefixIndex = -1;
bool splitNeedsInsertedHyphen = false;
// First line has reduced width due to text-indent
const int effectivePageWidth = isFirstLine ? pageWidth - firstLineIndent : pageWidth;
@@ -333,11 +385,15 @@ std::vector<size_t> ParsedText::computeHyphenatedLineBreaks(const GfxRenderer& r
const int availableWidth = effectivePageWidth - lineWidth - spacing;
const bool allowFallbackBreaks = isFirstWord; // Only for first word on line
if (availableWidth > 0 &&
hyphenateWordAtIndex(currentIndex, availableWidth, renderer, fontId, wordWidths, allowFallbackBreaks)) {
bool insertedHyphen = false;
if (availableWidth > 0 && hyphenateWordAtIndex(currentIndex, availableWidth, renderer, fontId, wordWidths,
allowFallbackBreaks, &insertedHyphen)) {
// Keep interWordGaps in sync: insert placeholder for the new remainder word.
// The remainder is always the first word on the next line so this slot is never read.
interWordGaps.insert(interWordGaps.begin() + currentIndex + 1, 0);
lineEndedWithHyphenation = true;
splitPrefixIndex = static_cast<int>(currentIndex);
splitNeedsInsertedHyphen = insertedHyphen;
// Prefix now fits; append it to this line and move to next line
lineWidth += spacing + wordWidths[currentIndex];
++currentIndex;
@@ -358,7 +414,17 @@ std::vector<size_t> ParsedText::computeHyphenatedLineBreaks(const GfxRenderer& r
--currentIndex;
}
if (lineEndedWithHyphenation &&
(splitPrefixIndex < static_cast<int>(lineStart) || splitPrefixIndex >= static_cast<int>(currentIndex))) {
lineEndedWithHyphenation = false;
splitPrefixIndex = -1;
splitNeedsInsertedHyphen = false;
}
lineBreakIndices.push_back(currentIndex);
lineEndsWithHyphenatedWord.push_back(lineEndedWithHyphenation);
splitPrefixWordIndexes.push_back(splitPrefixIndex);
splitInsertedHyphen.push_back(splitNeedsInsertedHyphen);
isFirstLine = false;
}
@@ -369,7 +435,7 @@ std::vector<size_t> ParsedText::computeHyphenatedLineBreaks(const GfxRenderer& r
// available width.
bool ParsedText::hyphenateWordAtIndex(const size_t wordIndex, const int availableWidth, const GfxRenderer& renderer,
const int fontId, std::vector<uint16_t>& wordWidths,
const bool allowFallbackBreaks) {
const bool allowFallbackBreaks, bool* outInsertedHyphen) {
// Guard against invalid indices or zero available width before attempting to split.
if (availableWidth <= 0 || wordIndex >= words.size()) {
return false;
@@ -448,13 +514,18 @@ bool ParsedText::hyphenateWordAtIndex(const size_t wordIndex, const int availabl
wordWidths[wordIndex] = static_cast<uint16_t>(chosenWidth);
const uint16_t remainderWidth = measureWordWidth(renderer, fontId, remainder, style);
wordWidths.insert(wordWidths.begin() + wordIndex + 1, remainderWidth);
if (outInsertedHyphen) {
*outInsertedHyphen = chosenNeedsHyphen;
}
return true;
}
void ParsedText::extractLine(const size_t breakIndex, const int pageWidth, const std::vector<uint16_t>& wordWidths,
const std::vector<bool>& continuesVec, const std::vector<size_t>& lineBreakIndices,
const std::function<void(std::shared_ptr<TextBlock>)>& processLine,
const GfxRenderer& renderer, const int fontId) {
ParsedText::LineProcessResult ParsedText::extractLine(
const size_t breakIndex, const int pageWidth, const std::vector<uint16_t>& wordWidths,
const std::vector<bool>& continuesVec, const std::vector<size_t>& lineBreakIndices,
const std::function<LineProcessResult(std::shared_ptr<TextBlock>, bool, bool)>& processLine,
const GfxRenderer& renderer, const int fontId, const bool lineEndsWithHyphenatedWord,
const bool suppressHyphenationRetry) {
const size_t lineBreak = lineBreakIndices[breakIndex];
const size_t lastBreakAt = breakIndex > 0 ? lineBreakIndices[breakIndex - 1] : 0;
const size_t lineWordCount = lineBreak - lastBreakAt;
@@ -552,6 +623,7 @@ void ParsedText::extractLine(const size_t breakIndex, const int pageWidth, const
}
}
processLine(
std::make_shared<TextBlock>(std::move(lineWords), std::move(lineXPos), std::move(lineWordStyles), blockStyle));
return processLine(
std::make_shared<TextBlock>(std::move(lineWords), std::move(lineXPos), std::move(lineWordStyles), blockStyle),
lineEndsWithHyphenatedWord, suppressHyphenationRetry);
}