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Fix rare painting glitch with image rotated 90 degrees
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@jdpurcell
jdpurcell committed Jan 1, 2025
1 parent f676d49 commit 7f6c590
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Showing 2 changed files with 52 additions and 32 deletions.
74 changes: 44 additions & 30 deletions src/qvgraphicsview.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -337,7 +337,7 @@ void QVGraphicsView::keyPressEvent(QKeyEvent *event)
if (scrollXSmallSteps != 0 || scrollYSmallSteps != 0 || scrollYLargeSteps != 0)
{
const QPoint delta {
(horizontalScrollBar()->singleStep() * scrollXSmallSteps) * (isRightToLeft() ? -1 : 1),
(horizontalScrollBar()->singleStep() * scrollXSmallSteps) * getRtlFlip(),
(verticalScrollBar()->singleStep() * scrollYSmallSteps) + (verticalScrollBar()->pageStep() * scrollYLargeSteps)
};
scrollHelper->move(delta);
Expand Down Expand Up @@ -384,7 +384,7 @@ void QVGraphicsView::executeDragAction(const Qv::ViewportDragAction action, cons
{
if (action == Qv::ViewportDragAction::Pan)
{
scrollHelper->move(QPointF(-delta.x() * (isRightToLeft() ? -1 : 1), -delta.y()));
scrollHelper->move(QPointF(-delta.x() * getRtlFlip(), -delta.y()));
}
else if (action == Qv::ViewportDragAction::MoveWindow)
{
Expand All @@ -403,7 +403,7 @@ void QVGraphicsView::executeDragAction(const Qv::ViewportDragAction action, cons
void QVGraphicsView::executeScrollAction(const Qv::ViewportScrollAction action, const QPoint delta, const QPoint mousePos, const bool hasShiftModifier)
{
const int deltaPerWheelStep = 120;
const int rtlFlip = isRightToLeft() ? -1 : 1;
const int rtlFlip = getRtlFlip();

const auto getUniAxisDelta = [delta, rtlFlip]() {
return
Expand Down Expand Up @@ -612,7 +612,7 @@ void QVGraphicsView::zoomAbsolute(const qreal absoluteLevel, const std::optional
if (pos.has_value())
{
const QPointF move = mapFromScene(scenePos) - pos.value();
horizontalScrollBar()->setValue(horizontalScrollBar()->value() + (move.x() * (isRightToLeft() ? -1 : 1)));
horizontalScrollBar()->setValue(horizontalScrollBar()->value() + (move.x() * getRtlFlip()));
verticalScrollBar()->setValue(verticalScrollBar()->value() + move.y());
lastZoomRoundingError = mapToScene(pos.value()) - scenePos;
constrainBoundsTimer->start();
Expand Down Expand Up @@ -834,7 +834,7 @@ const QJsonObject QVGraphicsView::getSessionState() const
{
QJsonObject state;

const QTransform transform = getTransformWithNoScaling();
const QTransform transform = getUnspecializedTransform();
const QJsonArray transformValues {
static_cast<int>(transform.m11()),
static_cast<int>(transform.m22()),
Expand Down Expand Up @@ -924,7 +924,7 @@ bool QVGraphicsView::isExpensiveScalingRequested() const

QSizeF QVGraphicsView::getEffectiveOriginalSize() const
{
return getTransformWithNoScaling().mapRect(QRectF(QPoint(), getCurrentFileDetails().loadedPixmapSize)).size() * getDpiAdjustment();
return getUnspecializedTransform().mapRect(QRectF(QPoint(), getCurrentFileDetails().loadedPixmapSize)).size() * getDpiAdjustment();
}

LogicalPixelFitter QVGraphicsView::getPixelFitter() const
Expand All @@ -936,7 +936,7 @@ LogicalPixelFitter QVGraphicsView::getPixelFitter() const
void QVGraphicsView::matchContentCenter(const QRect target)
{
const QPointF delta = QRectF(getContentRect()).center() - QRectF(target).center();
scrollHelper->move(QPointF(delta.x() * (isRightToLeft() ? -1 : 1), delta.y()));
scrollHelper->move(QPointF(delta.x() * getRtlFlip(), delta.y()));
}

QRect QVGraphicsView::getContentRect() const
Expand All @@ -945,18 +945,12 @@ QRect QVGraphicsView::getContentRect() const
// which introduces a rounding error to begin with, and even worse, the error will be magnified if we're in the
// the process of zooming in and haven't re-applied the expensive scaling yet. If that's the case, callers need
// to know what the content rect will be once the dust settles rather than what's being temporarily displayed.
const QRectF loadedPixmapBoundingRect = QRectF(QPoint(), getCurrentFileDetails().loadedPixmapSize);
const qreal effectiveTransformScale = zoomLevel * appliedDpiAdjustment;
const QTransform effectiveTransform = getTransformWithNoScaling().scale(effectiveTransformScale, effectiveTransformScale);
const QRectF contentRect = effectiveTransform.mapRect(loadedPixmapBoundingRect);
const QSize snappedSize = getPixelFitter().snapSize(contentRect.size());
const bool isHorizontalReversed = effectiveTransform.m11() < 0 || effectiveTransform.m21() < 0;
const bool isVerticalReversed = effectiveTransform.m22() < 0 || effectiveTransform.m12() < 0;
const QPointF topLeftCorrection = QPointF(
isHorizontalReversed ? contentRect.width() - snappedSize.width() : 0,
isVerticalReversed ? contentRect.height() - snappedSize.height() : 0
);
return QRect((contentRect.topLeft() + topLeftCorrection).toPoint(), snappedSize);
const QSizeF pixmapSize = getCurrentFileDetails().loadedPixmapSize;
const QRectF pixmapBoundingRect = QRectF(QPoint(), pixmapSize);
const qreal pixmapScale = zoomLevel * appliedDpiAdjustment;
const QTransform pixmapTransform = normalizeTransformOrigin(getUnspecializedTransform().scale(pixmapScale, pixmapScale), pixmapSize);
const QRectF contentRect = pixmapTransform.mapRect(pixmapBoundingRect);
return QRect(contentRect.topLeft().toPoint(), getPixelFitter().snapSize(contentRect.size()));
}

QRect QVGraphicsView::getUsableViewportRect(const bool addOverscan) const
Expand All @@ -968,24 +962,39 @@ QRect QVGraphicsView::getUsableViewportRect(const bool addOverscan) const
return rect;
}

void QVGraphicsView::setTransformScale(qreal value)
void QVGraphicsView::setTransformScale(const qreal value)
{
setTransform(getTransformWithNoScaling().scale(value, value));
setTransformWithNormalization(getUnspecializedTransform().scale(value, value));
}

QTransform QVGraphicsView::getTransformWithNoScaling() const
void QVGraphicsView::setTransformWithNormalization(const QTransform &matrix)
{
setTransform(normalizeTransformOrigin(matrix, loadedPixmapItem->boundingRect().size()));
}

QTransform QVGraphicsView::getUnspecializedTransform() const
{
// Returns a transform that represents the currently applied mirroring, flipping, and rotation
// (only in increments of 90 degrees) operations, but with no scaling or translation.
const QTransform t = transform();
// Only intended to handle combinations of scaling, mirroring, flipping, and rotation
// in increments of 90 degrees. A seemingly simpler approach would be to scale the
// transform by the inverse of its scale factor, but the resulting scale factor may
// not exactly equal 1 due to floating point rounding errors.
if (t.type() == QTransform::TxRotate)
return { 0, t.m12() < 0 ? -1.0 : 1.0, t.m21() < 0 ? -1.0 : 1.0, 0, 0, 0 };
else
return { t.m11() < 0 ? -1.0 : 1.0, 0, 0, t.m22() < 0 ? -1.0 : 1.0, 0, 0 };
}

QTransform QVGraphicsView::normalizeTransformOrigin(const QTransform &matrix, const QSizeF &pixmapSize) const
{
// This applies translation to compensate for mirroring, flipping, and rotation to ensure that
// a pixmap will have its resulting top left at 0, 0. In theory this shouldn't matter, but it
// works around a glitch where Qt sometimes won't paint the last pixel on the right of the
// viewport if an image is rotated 90 degrees and just touching the right edge.
const int horizontalFactor = matrix.m11() < 0 ? -1 * getRtlFlip() : matrix.m12() < 0 ? -1 : 0;
const int verticalFactor = matrix.m22() < 0 ? -1 : matrix.m21() < 0 ? -1 * getRtlFlip() : 0;
QTransform t { matrix.m11(), matrix.m12(), matrix.m21(), matrix.m22(), 0, 0 };
return t.translate(pixmapSize.width() * horizontalFactor, pixmapSize.height() * verticalFactor);
}

qreal QVGraphicsView::getDpiAdjustment() const
{
// Although inverting this potentially introduces a rounding error, it is inevitable. For
Expand Down Expand Up @@ -1017,6 +1026,11 @@ void QVGraphicsView::handleSmoothScalingChange()
removeExpensiveScaling();
}

int QVGraphicsView::getRtlFlip() const
{
return isRightToLeft() ? -1 : 1;
}

void QVGraphicsView::cancelTurboNav()
{
if (!turboNavMode.has_value())
Expand Down Expand Up @@ -1131,23 +1145,23 @@ void QVGraphicsView::rotateImage(const int relativeAngle)
const QRect oldRect = getContentRect();
const QTransform t = transform();
const bool isMirroredOrFlipped = t.isRotating() ? ((t.m12() < 0) == (t.m21() < 0)) : ((t.m11() < 0) != (t.m22() < 0));
rotate(relativeAngle * (isMirroredOrFlipped ? -1 : 1));
setTransformWithNormalization(transform().rotate(relativeAngle * (isMirroredOrFlipped ? -1 : 1)));
matchContentCenter(oldRect);
}

void QVGraphicsView::mirrorImage()
{
const QRect oldRect = getContentRect();
const int rotateCorrection = transform().isRotating() ? -1 : 1;
scale(-1 * rotateCorrection, 1 * rotateCorrection);
setTransformWithNormalization(transform().scale(-1 * rotateCorrection, 1 * rotateCorrection));
matchContentCenter(oldRect);
}

void QVGraphicsView::flipImage()
{
const QRect oldRect = getContentRect();
const int rotateCorrection = transform().isRotating() ? -1 : 1;
scale(1 * rotateCorrection, -1 * rotateCorrection);
setTransformWithNormalization(transform().scale(1 * rotateCorrection, -1 * rotateCorrection));
matchContentCenter(oldRect);
}

Expand All @@ -1156,6 +1170,6 @@ void QVGraphicsView::resetTransformation()
const QRect oldRect = getContentRect();
const QTransform t = transform();
const qreal scale = qFabs(t.isRotating() ? t.m21() : t.m11());
setTransform(QTransform::fromScale(scale, scale));
setTransformWithNormalization(QTransform::fromScale(scale, scale));
matchContentCenter(oldRect);
}
10 changes: 8 additions & 2 deletions src/qvgraphicsview.h
View file
Original file line number Diff line number Diff line change
Expand Up @@ -144,16 +144,22 @@ class QVGraphicsView : public QGraphicsView

QRect getUsableViewportRect(const bool addOverscan = false) const;

void setTransformScale(qreal absoluteScale);
void setTransformScale(const qreal absoluteScale);

QTransform getTransformWithNoScaling() const;
void setTransformWithNormalization(const QTransform &matrix);

QTransform getUnspecializedTransform() const;

QTransform normalizeTransformOrigin(const QTransform &matrix, const QSizeF &pixmapSize) const;

qreal getDpiAdjustment() const;

void handleDpiAdjustmentChange();

void handleSmoothScalingChange();

int getRtlFlip() const;

void cancelTurboNav();

MainWindow* getMainWindow() const;
Expand Down

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