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fix: caching scaled image to avoid lagging when panning large image

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This commit is contained in:
Gary Wang 2022-04-03 19:08:14 +08:00
parent c9dadcbcad
commit 6270910e12
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GPG Key ID: 5D30A4F15EA78760
1 changed files with 15 additions and 6 deletions
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21
app/graphicsscene.cpp
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@ -21,6 +21,18 @@ public:
m_scaleHint = scaleHint;
}
const QPixmap & scaledPixmap(float scaleHint) {
if (qFuzzyCompare(scaleHint, m_cachedScaleHint)) return m_cachedPixmap;
QSizeF resizedScale(boundingRect().size());
resizedScale *= scaleHint;
m_cachedPixmap = pixmap().scaled(
resizedScale.toSize(),
Qt::KeepAspectRatio,
Qt::SmoothTransformation);
m_cachedScaleHint = scaleHint;
return m_cachedPixmap;
}
void paint(QPainter *painter, const QStyleOptionGraphicsItem *option,
QWidget *widget) override
{
@ -28,18 +40,15 @@ public:
return QGraphicsPixmapItem::paint(painter, option, widget);
} else {
// painter->setRenderHints(QPainter::Antialiasing);
QSizeF resizedScale(boundingRect().size());
resizedScale *= m_scaleHint;
painter->drawPixmap(QRectF(offset(), boundingRect().size()).toRect(),
pixmap().scaled(resizedScale.toSize(),
Qt::KeepAspectRatio,
Qt::SmoothTransformation)
);
scaledPixmap(m_scaleHint));
}
}
private:
float m_scaleHint = 1;
float m_cachedScaleHint = -1;
QPixmap m_cachedPixmap;
};
GraphicsScene::GraphicsScene(QObject *parent)