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Implement a small cache to avoid scaling continuously while painting

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luisangelsm
2026-02-26 16:41:43 +01:00
committed by Luis Ángel San Martín
parent 0bd291ba98
commit edbbc3c577
2 changed files with 105 additions and 4 deletions
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54
YACReader/continuous_page_widget.cpp
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@ -42,6 +42,7 @@ void ContinuousPageWidget::setViewModel(ContinuousViewModel *viewModel)
}
updateGeometry();
scaledPageCache.invalidateAll();
update();
}
@ -49,6 +50,7 @@ void ContinuousPageWidget::reset()
{
setMinimumHeight(0);
setMaximumHeight(QWIDGETSIZE_MAX);
scaledPageCache.invalidateAll();
updateGeometry();
update();
}
@ -86,6 +88,8 @@ void ContinuousPageWidget::onPageAvailable(int absolutePageIndex)
return;
}
scaledPageCache.invalidatePage(absolutePageIndex);
// repaint the region where this page lives
if (absolutePageIndex < continuousViewModel->numPages()) {
QSize scaled = continuousViewModel->scaledPageSize(absolutePageIndex);
@ -106,10 +110,17 @@ void ContinuousPageWidget::paintEvent(QPaintEvent *event)
}
QPainter painter(this);
scaledPageCache.invalidateForWidth(width());
QRect visibleRect = event->rect();
int firstPage = continuousViewModel->pageAtY(visibleRect.top());
int lastPage = continuousViewModel->pageAtY(visibleRect.bottom());
firstPage = qBound(0, firstPage, continuousViewModel->numPages() - 1);
lastPage = qBound(0, lastPage, continuousViewModel->numPages() - 1);
const int cacheMin = std::max(0, firstPage - 1);
const int cacheMax = std::min(continuousViewModel->numPages() - 1, lastPage + 1);
scaledPageCache.keepOnlyRange(cacheMin, cacheMax);
int w = width();
for (int i = firstPage; i <= lastPage && i < continuousViewModel->numPages(); ++i) {
@ -124,10 +135,9 @@ void ContinuousPageWidget::paintEvent(QPaintEvent *event)
const QImage *img = render->bufferedImage(i);
if (img && !img->isNull()) {
if (img->size() != scaled) {
painter.drawImage(pageRect, img->scaled(scaled, Qt::IgnoreAspectRatio, Qt::SmoothTransformation));
} else {
painter.drawImage(pageRect, *img);
const QImage *drawable = scaledImageForPaint(i, img, scaled, width());
if (drawable) {
painter.drawImage(pageRect, *drawable);
}
} else {
// placeholder
@ -145,3 +155,39 @@ void ContinuousPageWidget::resizeEvent(QResizeEvent *event)
continuousViewModel->setViewportSize(width(), continuousViewModel->viewportHeight());
}
}
const QImage *ContinuousPageWidget::scaledImageForPaint(int pageIndex, const QImage *source, const QSize &targetSize, int effectiveWidth)
{
if (!source || source->isNull() || targetSize.isEmpty()) {
return nullptr;
}
if (source->size() == targetSize) {
return source;
}
scaledPageCache.invalidateForWidth(effectiveWidth);
auto it = scaledPageCache.pages.find(pageIndex);
const qint64 sourceKey = source->cacheKey();
if (it != scaledPageCache.pages.end()) {
const ScaledPageCacheEntry &entry = it.value();
const bool validEntry = entry.sourceCacheKey == sourceKey
&& entry.sourceSize == source->size()
&& entry.targetSize == targetSize
&& !entry.scaledImage.isNull();
if (validEntry) {
return &it.value().scaledImage;
}
}
ScaledPageCacheEntry entry;
entry.sourceCacheKey = sourceKey;
entry.sourceSize = source->size();
entry.targetSize = targetSize;
entry.scaledImage = source->scaled(targetSize, Qt::IgnoreAspectRatio, Qt::SmoothTransformation);
scaledPageCache.pages.insert(pageIndex, std::move(entry));
return &scaledPageCache.pages[pageIndex].scaledImage;
}