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Rasterizer: compute intersection factors only when needed 

Fixes oss-fuzz issue 29285

Pick-to: 6.0
Change-Id: I8f7e0bc898b119d153a36cef5a74371249ed7686
Reviewed-by: Allan Sandfeld Jensen <allan.jensen@qt.io>
Reviewed-by: Robert Loehning <robert.loehning@qt.io>
bb10
Eirik Aavitsland 2021-01-20 08:35:43 +01:00
parent f9fff26b2d
commit e1ed570f9d
1 changed files with 12 additions and 7 deletions
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19
src/gui/painting/qrasterizer.cpp
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@ -657,19 +657,22 @@ static QScFixed intersectPixelFP(int x, QScFixed top, QScFixed bottom, QScFixed
QScFixed rightX = IntToQScFixed(x) + QScFixedFactor;
QScFixed leftIntersectY, rightIntersectY;
if (slope > 0) {
leftIntersectY = top + QScFixedMultiply(leftX - leftIntersectX, invSlope);
rightIntersectY = leftIntersectY + invSlope;
} else {
leftIntersectY = top + QScFixedMultiply(leftX - rightIntersectX, invSlope);
rightIntersectY = leftIntersectY + invSlope;
}
auto computeIntersectY = [&]() {
if (slope > 0) {
leftIntersectY = top + QScFixedMultiply(leftX - leftIntersectX, invSlope);
rightIntersectY = leftIntersectY + invSlope;
} else {
leftIntersectY = top + QScFixedMultiply(leftX - rightIntersectX, invSlope);
rightIntersectY = leftIntersectY + invSlope;
}
};
if (leftIntersectX >= leftX && rightIntersectX <= rightX) {
return QScFixedMultiply(bottom - top, leftIntersectX - leftX + ((rightIntersectX - leftIntersectX) >> 1));
} else if (leftIntersectX >= rightX) {
return bottom - top;
} else if (leftIntersectX >= leftX) {
computeIntersectY();
if (slope > 0) {
return (bottom - top) - QScFixedFastMultiply((rightX - leftIntersectX) >> 1, rightIntersectY - top);
} else {
@ -678,12 +681,14 @@ static QScFixed intersectPixelFP(int x, QScFixed top, QScFixed bottom, QScFixed
} else if (rightIntersectX <= leftX) {
return 0;
} else if (rightIntersectX <= rightX) {
computeIntersectY();
if (slope > 0) {
return QScFixedFastMultiply((rightIntersectX - leftX) >> 1, bottom - leftIntersectY);
} else {
return QScFixedFastMultiply((rightIntersectX - leftX) >> 1, leftIntersectY - top);
}
} else {
computeIntersectY();
if (slope > 0) {
return (bottom - rightIntersectY) + ((rightIntersectY - leftIntersectY) >> 1);
} else {