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Fix Qt 6 performance regression when painting outside device

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Painting wide lines and filling would be clipped to cliprect (by
default, the device rect) only if the bounding rect coordinates
exceeded QT_RASTER_COORD_LIMIT. In Qt 6, that limit was raised from
2^15 to 2^23, so a lot of time could be spent on rasterizing elements
that would anyway be outside the rendering area.

Fix by instead clipping whenever the path to be painted overshoots the
cliprect by a significant margin. At this point, the path is already
flattened to straight lines, so clipping is quick and precise. Testing
indicates that this solution improves performance a lot when large
portions of the elements to be painted fall outside the cliprect,
while not causing significant performance hits otherwise.

As a side effect, it is then no longer necessary to test the bounding
rect explicitly against QT_RASTER_COORD_LIMIT, since we already make
sure that the clip rect we check against is within that limit.

Fixes: QTBUG-110595
Pick-to: 6.5 6.4 6.2
Change-Id: Iaf1afbb481c2d7059405f334278796ad46f5bcb6
Reviewed-by: Allan Sandfeld Jensen <allan.jensen@qt.io>
This commit is contained in:
Eirik Aavitsland 2023-01-31 10:57:26 +01:00
parent 08c2010708
commit ce7b4c734b
3 changed files with 24 additions and 17 deletions
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30
src/gui/painting/qoutlinemapper.cpp
View File

@ -37,6 +37,24 @@ static const QRectF boundingRect(const QPointF *points, int pointCount)
return QRectF(QPointF(minx, miny), QPointF(maxx, maxy));
}
void QOutlineMapper::setClipRect(QRect clipRect)
{
auto limitCoords = [](QRect r) {
const QRect limitRect(QPoint(-QT_RASTER_COORD_LIMIT, -QT_RASTER_COORD_LIMIT),
QPoint(QT_RASTER_COORD_LIMIT, QT_RASTER_COORD_LIMIT));
r &= limitRect;
r.setWidth(qMin(r.width(), QT_RASTER_COORD_LIMIT));
r.setHeight(qMin(r.height(), QT_RASTER_COORD_LIMIT));
return r;
};
if (clipRect != m_clip_rect) {
m_clip_rect = limitCoords(clipRect);
const int mw = 64; // margin width. No need to trigger clipping for slight overshooting
m_clip_trigger_rect = QRectF(limitCoords(m_clip_rect.adjusted(-mw, -mw, mw, mw)));
}
}
void QOutlineMapper::curveTo(const QPointF &cp1, const QPointF &cp2, const QPointF &ep) {
#ifdef QT_DEBUG_CONVERT
printf("QOutlineMapper::curveTo() (%f, %f)\n", ep.x(), ep.y());
@ -200,16 +218,8 @@ void QOutlineMapper::endOutline()
m_clip_rect.x(), m_clip_rect.y(), m_clip_rect.width(), m_clip_rect.height());
#endif
// Check for out of dev bounds...
const bool do_clip = !m_in_clip_elements && ((controlPointRect.left() < -QT_RASTER_COORD_LIMIT
|| controlPointRect.right() > QT_RASTER_COORD_LIMIT
|| controlPointRect.top() < -QT_RASTER_COORD_LIMIT
|| controlPointRect.bottom() > QT_RASTER_COORD_LIMIT
|| controlPointRect.width() > QT_RASTER_COORD_LIMIT
|| controlPointRect.height() > QT_RASTER_COORD_LIMIT));
if (do_clip) {
// Avoid rasterizing outside cliprect: faster, and ensures coords < QT_RASTER_COORD_LIMIT
if (!m_in_clip_elements && !m_clip_trigger_rect.contains(controlPointRect)) {
clipElements(elements, elementTypes(), m_elements.size());
} else {
convertElements(elements, elementTypes(), m_elements.size());

3
src/gui/painting/qoutlinemapper_p.h
View File

@ -79,6 +79,8 @@ public:
m_curve_threshold = scale == 0 ? qreal(0.25) : (qreal(0.25) / scale);
}
void setClipRect(QRect clipRect);
void beginOutline(Qt::FillRule fillRule)
{
#ifdef QT_DEBUG_CONVERT
@ -163,6 +165,7 @@ public:
QDataBuffer<int> m_contours;
QRect m_clip_rect;
QRectF m_clip_trigger_rect;
QRectF controlPointRect; // only valid after endOutline()
QT_FT_Outline m_outline;

8
src/gui/painting/qpaintengine_raster.cpp
View File

@ -406,13 +406,7 @@ bool QRasterPaintEngine::begin(QPaintDevice *device)
QRasterPaintEngineState *s = state();
ensureOutlineMapper();
d->outlineMapper->m_clip_rect = d->deviceRect;
if (d->outlineMapper->m_clip_rect.width() > QT_RASTER_COORD_LIMIT)
d->outlineMapper->m_clip_rect.setWidth(QT_RASTER_COORD_LIMIT);
if (d->outlineMapper->m_clip_rect.height() > QT_RASTER_COORD_LIMIT)
d->outlineMapper->m_clip_rect.setHeight(QT_RASTER_COORD_LIMIT);
d->outlineMapper->setClipRect(d->deviceRect);
d->rasterizer->setClipRect(d->deviceRect);
s->penData.init(d->rasterBuffer.data(), this);