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feat(DrawUtils): add drawInsetShadow for inner shadow rendering #779

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feat(DrawUtils): add drawInsetShadow for inner shadow rendering #779

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1 change: 1 addition & 0 deletions include/widgets/dstyle.h
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Original file line number Diff line number Diff line change
Expand Up @@ -45,6 +45,7 @@ Q_DECLARE_FLAGS(Corners, Corner)

void drawShadow(QPainter *pa, const QRect &rect, qreal xRadius, qreal yRadius, const QColor &sc, qreal radius, const QPoint &offset);
void drawShadow(QPainter *pa, const QRect &rect, const QPainterPath &path, const QColor &sc, int radius, const QPoint &offset);
void drawInsetShadow(QPainter *pa, const QRect &rect, qreal xRadius, qreal yRadius, const QColor &sc, qreal radius, const QPoint &offset);
void drawRoundedRect(QPainter *pa, const QRect &rect, qreal xRadius, qreal yRadius, Corners corners, Qt::SizeMode mode = Qt::AbsoluteSize);
void drawFork(QPainter *pa, const QRectF &rect, const QColor &color, int width = 2);
void drawMark(QPainter *pa, const QRectF &rect, const QColor &boxInside, const QColor &boxOutside, const int penWidth, const int outLineLeng = 2);
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55 changes: 55 additions & 0 deletions src/widgets/dstyle.cpp
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Expand Up @@ -392,7 +392,62 @@
pa->drawPixmap(shadow_rect, shadow);
}

void drawInsetShadow(QPainter *pa, const QRect &rect, qreal xRadius, qreal yRadius, const QColor &sc, qreal radius, const QPoint &offset)

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The function 'drawInsetShadow' is never used.
{
if (radius <= 0 || rect.isNull())
return;

qreal scale = pa->paintEngine()->paintDevice()->devicePixelRatioF();
QSize size = rect.size() * scale;
xRadius *= scale;
yRadius *= scale;
radius *= scale;
QPoint scaledOffset(offset.x() * scale, offset.y() * scale);

@sourcery-ai sourcery-ai Bot Sep 3, 2026

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issue (bug_risk): The offset is multiplied by the device-pixel ratio and then truncated when constructing the QPoint, so a logical offset of 1 pixel becomes 1 physical pixel rather than 1.5 pixels on a 1.5x display. The inset shadow therefore has an incorrect offset on fractional-DPR devices.

Triggers: When the painter targets a device with a fractional device-pixel ratio and offset is nonzero.

Suggested fix: Use a QPointF for the scaled offset, or round the scaled components explicitly before drawing.

Suggested change
QPoint scaledOffset(offset.x() * scale, offset.y() * scale);
QPointF scaledOffset(offset.x() * scale, offset.y() * scale);


// Build an opaque image, then cut out a rounded-rect hole shifted by
// 'offset'. After blurring, the hole edges fade inward, producing an
// inset shadow. Positive offset.y() makes the shadow stronger at the
// top edge; negative at the bottom.
QImage shadow_base(size, QImage::Format_ARGB32_Premultiplied);
shadow_base.fill(Qt::black);

QPainter holePainter(&shadow_base);
holePainter.setRenderHint(QPainter::Antialiasing, true);
holePainter.setPen(Qt::NoPen);
holePainter.setCompositionMode(QPainter::CompositionMode_Clear);
holePainter.setBrush(Qt::transparent);
QRectF holeRect = QRectF(shadow_base.rect()).translated(scaledOffset);
holeRect = holeRect.marginsRemoved(QMarginsF(radius, radius, radius, radius));
holePainter.drawRoundedRect(holeRect, xRadius, yRadius);
holePainter.end();

// Blur the alpha channel so the hole edges become a soft gradient.
QImage blurred(size, QImage::Format_ARGB32_Premultiplied);
blurred.fill(0);
QPainter blurPainter(&blurred);
qt_blurImage(&blurPainter, shadow_base, radius, false, true);
blurPainter.end();

// Replace the placeholder black with the actual shadow color.
QPainter colorPainter(&blurred);
colorPainter.setCompositionMode(QPainter::CompositionMode_SourceIn);
colorPainter.fillRect(blurred.rect(), sc);
colorPainter.end();

blurred.setDevicePixelRatio(scale);

// Clip to the rounded-rect shape so the opaque outer area is hidden;
// only the inward-fading shadow at the edges is visible.
pa->save();
pa->setRenderHint(QPainter::Antialiasing, true);
QPainterPath clipPath;
clipPath.addRoundedRect(rect, xRadius / scale, yRadius / scale);
pa->setClipPath(clipPath);
pa->drawImage(rect.topLeft(), blurred);
pa->restore();
}

void drawFork(QPainter *pa, const QRectF &rect, const QColor &color, int width)

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The function 'drawFork' is never used.
{
QPen pen;
pen.setWidth(width);
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