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Fix koreader sync regresssion

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This commit is contained in:
jpirnay
2026-05-23 13:20:01 +02:00
parent 6717c02173
commit ff93b152a3
6 changed files with 390 additions and 127 deletions
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lib/KOReaderSync/ProgressMapper.cpp
+98 -12
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@@ -43,6 +43,60 @@ bool resolveFromPercentage(const std::shared_ptr<Epub>& epub, const float percen
return true;
}
// Compute intra-spine progress from KOReader's book percentage, assuming the target
// spine is known. This is the constrained version of resolveFromPercentage that
// honors an XPath-derived spine index even when the heavy XPath resolver couldn't
// run (typically because heap was too fragmented to inflate the chapter at sync time).
//
// The math is identical to the per-spine portion of resolveFromPercentage. Returns 0
// when the percentage maps to bytes before the spine's start (the position lives
// inside the spine by assumption, so clamp to 0) and 1 when it overshoots the end.
float intraSpineFromPercentage(const std::shared_ptr<Epub>& epub, const int spineIndex, const float percentage) {
if (!epub || spineIndex < 0 || spineIndex >= epub->getSpineItemsCount() || !std::isfinite(percentage)) {
return 0.0f;
}
const size_t bookSize = epub->getBookSize();
if (bookSize == 0) {
return 0.0f;
}
const float sanitized = std::clamp(percentage, 0.0f, 1.0f);
const size_t targetBytes = static_cast<size_t>(bookSize * sanitized);
const size_t prevCumSize = (spineIndex > 0) ? epub->getCumulativeSpineItemSize(spineIndex - 1) : 0;
const size_t currentCumSize = epub->getCumulativeSpineItemSize(spineIndex);
const size_t spineSize = currentCumSize - prevCumSize;
if (spineSize == 0) {
return 0.0f;
}
if (targetBytes <= prevCumSize) {
return 0.0f;
}
const size_t bytesIntoSpine = targetBytes - prevCumSize;
return std::clamp(static_cast<float>(bytesIntoSpine) / static_cast<float>(spineSize), 0.0f, 1.0f);
}
// KOReader emits chapter-start XPaths as ".../body/<wrapper>.0" or just
// ".../body/text()[1].0" — there's no paragraph segment, and the character offset is 0.
// These unambiguously denote "the start of the spine"; we can pin intra=0 without
// inflating the chapter. Catches the common case of starting a new chapter on
// another device, which previously round-tripped through book-percentage byte math
// and landed several pages into the chapter due to byte-vs-page-density skew.
bool isChapterStartXPath(const std::string& xpath) {
// Reject anything with a paragraph or list-item predicate — those carry real
// position information that can't be flattened to "start of spine".
if (xpath.find("/p[") != std::string::npos) return false;
if (xpath.find("/li[") != std::string::npos) return false;
// The path must end with a ".0" text-point segment. The reverse mapper already
// strips text() suffixes for matching, but here we look at the raw form: either
// "<tag>.0" (cursor at start of element) or "text()[1].0" / similar (cursor at
// start of the first text node) with no following character offset.
const size_t dotPos = xpath.rfind('.');
if (dotPos == std::string::npos || dotPos + 1 >= xpath.size()) return false;
for (size_t i = dotPos + 1; i < xpath.size(); i++) {
if (xpath[i] != '0') return false;
}
return true;
}
} // namespace
KOReaderPosition ProgressMapper::toKOReader(const std::shared_ptr<Epub>& epub, const CrossPointPosition& pos) {
@@ -101,9 +155,14 @@ CrossPointPosition ProgressMapper::toCrossPoint(const std::shared_ptr<Epub>& epu
bool usedXPathMapping = false;
bool usedPercentageReconcile = false;
// Mapping source used for the final log line; updated as we narrow down the path
// actually taken (xpath / xpath+percentage / xpath-spine+percentage / percentage).
const char* mappingSource = "percentage";
int xpathSpineIndex = -1;
if (ChapterXPathIndexer::tryExtractSpineIndexFromXPath(koPos.xpath, xpathSpineIndex) && xpathSpineIndex >= 0 &&
xpathSpineIndex < spineCount) {
const bool haveXPathSpine = ChapterXPathIndexer::tryExtractSpineIndexFromXPath(koPos.xpath, xpathSpineIndex) &&
xpathSpineIndex >= 0 && xpathSpineIndex < spineCount;
if (haveXPathSpine) {
float intraFromXPath = 0.0f;
uint16_t liIndexFromXPath = 0;
if (ChapterXPathIndexer::findProgressForXPath(epub, xpathSpineIndex, koPos.xpath, intraFromXPath, xpathExactMatch,
@@ -139,8 +198,12 @@ CrossPointPosition ProgressMapper::toCrossPoint(const std::shared_ptr<Epub>& epu
}
}
}
mappingSource = usedPercentageReconcile ? "xpath+percentage" : "xpath";
}
// Extract paragraph index from XPath for direct page lookup via section cache
// Extract paragraph index from XPath for direct page lookup via section cache.
// Done regardless of whether the heavy XPath resolver succeeded — the paragraph
// LUT lookup later (in EpubReaderActivity::NavigationTarget::resolveInto) snaps
// to the precise page, so even without intra resolution we get an exact landing.
uint16_t pIndex = 0;
if (ChapterXPathIndexer::tryExtractParagraphIndexFromXPath(koPos.xpath, pIndex)) {
result.paragraphIndex = pIndex;
@@ -149,14 +212,39 @@ CrossPointPosition ProgressMapper::toCrossPoint(const std::shared_ptr<Epub>& epu
}
if (!usedXPathMapping) {
int percentageSpineIndex = -1;
float percentageIntraSpine = -1.0f;
if (!resolveFromPercentage(epub, koPos.percentage, spineCount, percentageSpineIndex, percentageIntraSpine)) {
return result;
// Heavy XPath resolution failed (typically because heap was too fragmented to
// inflate the spine at sync time). Salvage as much as we can:
// 1) Trust the spine index extracted from the XPath itself — it's purely
// string-derived and always correct when present. Using it preserves
// cross-chapter syncs even when chapter content can't be re-parsed.
// 2) For chapter-start XPaths (ending in ".0" with no paragraph predicate),
// pin intra=0. KOReader's percentage carries small per-DOM rounding that
// would otherwise leak into a spurious intra > 0 via byte-fraction math.
// 3) Otherwise compute intra-spine from KOReader's percentage relative to
// the XPath-derived spine. Falls back to global percentage spine selection
// only when no XPath spine is available.
if (haveXPathSpine) {
result.spineIndex = xpathSpineIndex;
if (isChapterStartXPath(koPos.xpath)) {
resolvedIntraSpineProgress = 0.0f;
mappingSource = "xpath-spine+chapter-start";
LOG_DBG("ProgressMapper", "Chapter-start XPath '%s' on spine=%d, pinning intra=0", koPos.xpath.c_str(),
xpathSpineIndex);
} else {
resolvedIntraSpineProgress = intraSpineFromPercentage(epub, xpathSpineIndex, koPos.percentage);
mappingSource = "xpath-spine+percentage";
LOG_DBG("ProgressMapper", "XPath resolve unavailable for spine=%d; intra from pct=%.3f -> %.3f",
xpathSpineIndex, koPos.percentage, resolvedIntraSpineProgress);
}
} else {
int percentageSpineIndex = -1;
float percentageIntraSpine = -1.0f;
if (!resolveFromPercentage(epub, koPos.percentage, spineCount, percentageSpineIndex, percentageIntraSpine)) {
return result;
}
result.spineIndex = percentageSpineIndex;
resolvedIntraSpineProgress = percentageIntraSpine;
}
result.spineIndex = percentageSpineIndex;
resolvedIntraSpineProgress = percentageIntraSpine;
}
// Estimate page number within the selected spine item
@@ -207,8 +295,6 @@ CrossPointPosition ProgressMapper::toCrossPoint(const std::shared_ptr<Epub>& epu
result.spineIndex, resolvedIntraSpineProgress, result.hasParagraphIndex ? "yes" : "no", result.paragraphIndex,
result.hasListItemIndex ? "yes" : "no", result.listItemIndex);
const char* mappingSource =
usedXPathMapping ? (usedPercentageReconcile ? "xpath+percentage" : "xpath") : "percentage";
LOG_DBG("ProgressMapper", "KOReader -> CrossPoint: %.2f%% at %s -> spine=%d, page=%d (%s, exact=%s)",
koPos.percentage * 100, koPos.xpath.c_str(), result.spineIndex, result.pageNumber, mappingSource,
xpathExactMatch ? "yes" : "no");