From 85b4f0d2d3ffd326548ca8f0e15ac27f5fd8d77d Mon Sep 17 00:00:00 2001 From: Gunnar Sletta Date: Tue, 11 Jun 2013 11:09:34 +0200 Subject: Avoid floating point exceptions in rasterizeLine. Task-number: QTBUG-16757 Change-Id: I3ef988f1e039c12529d62197d85a62f201e4ae12 Reviewed-by: Lars Knoll --- src/gui/painting/qrasterizer.cpp | 61 +++++++++++++++++++++++++++++----------- 1 file changed, 45 insertions(+), 16 deletions(-) (limited to 'src/gui/painting/qrasterizer.cpp') diff --git a/src/gui/painting/qrasterizer.cpp b/src/gui/painting/qrasterizer.cpp index a6be7c6c78..197d49369e 100644 --- a/src/gui/painting/qrasterizer.cpp +++ b/src/gui/painting/qrasterizer.cpp @@ -734,6 +734,35 @@ static inline QPointF snapTo26Dot6Grid(const QPointF &p) qFloorF(p.y() * 64) * (1 / qreal(64))); } +/* + The rasterize line function relies on some div by zero which should + result in +/-inf values. However, when floating point exceptions are + enabled, this will cause crashes, so we return high numbers instead. + As the returned value is used in further arithmetic, returning + FLT_MAX/DBL_MAX will also cause values, so instead return a value + that is well outside the int-range. + */ +static inline qreal qSafeDivide(qreal x, qreal y) +{ + if (y == 0) + return x > 0 ? 1e20 : -1e20; + return x / y; +} + +/* Conversion to int fails if the value is too large to fit into INT_MAX or + too small to fit into INT_MIN, so we need this slightly safer conversion + when floating point exceptions are enabled + */ +static inline int qSafeFloatToQ16Dot16(qreal x) +{ + qreal tmp = x * 65536.; + if (tmp > qreal(INT_MAX)) + return INT_MAX; + else if (tmp < qreal(INT_MIN)) + return -INT_MAX; + return int(tmp); +} + void QRasterizer::rasterizeLine(const QPointF &a, const QPointF &b, qreal width, bool squareCap) { if (a == b || width == 0 || d->clipRect.isEmpty()) @@ -946,23 +975,23 @@ void QRasterizer::rasterizeLine(const QPointF &a, const QPointF &b, qreal width, const QPointF bottomLeftEdge = bottom - left; const QPointF bottomRightEdge = bottom - right; - const qreal topLeftSlope = topLeftEdge.x() / topLeftEdge.y(); - const qreal bottomLeftSlope = bottomLeftEdge.x() / bottomLeftEdge.y(); + const qreal topLeftSlope = qSafeDivide(topLeftEdge.x(), topLeftEdge.y()); + const qreal bottomLeftSlope = qSafeDivide(bottomLeftEdge.x(), bottomLeftEdge.y()); - const qreal topRightSlope = topRightEdge.x() / topRightEdge.y(); - const qreal bottomRightSlope = bottomRightEdge.x() / bottomRightEdge.y(); + const qreal topRightSlope = qSafeDivide(topRightEdge.x(), topRightEdge.y()); + const qreal bottomRightSlope = qSafeDivide(bottomRightEdge.x(), bottomRightEdge.y()); - const Q16Dot16 topLeftSlopeFP = FloatToQ16Dot16(topLeftSlope); - const Q16Dot16 topRightSlopeFP = FloatToQ16Dot16(topRightSlope); + const Q16Dot16 topLeftSlopeFP = qSafeFloatToQ16Dot16(topLeftSlope); + const Q16Dot16 topRightSlopeFP = qSafeFloatToQ16Dot16(topRightSlope); - const Q16Dot16 bottomLeftSlopeFP = FloatToQ16Dot16(bottomLeftSlope); - const Q16Dot16 bottomRightSlopeFP = FloatToQ16Dot16(bottomRightSlope); + const Q16Dot16 bottomLeftSlopeFP = qSafeFloatToQ16Dot16(bottomLeftSlope); + const Q16Dot16 bottomRightSlopeFP = qSafeFloatToQ16Dot16(bottomRightSlope); - const Q16Dot16 invTopLeftSlopeFP = FloatToQ16Dot16(1 / topLeftSlope); - const Q16Dot16 invTopRightSlopeFP = FloatToQ16Dot16(1 / topRightSlope); + const Q16Dot16 invTopLeftSlopeFP = qSafeFloatToQ16Dot16(qSafeDivide(1, topLeftSlope)); + const Q16Dot16 invTopRightSlopeFP = qSafeFloatToQ16Dot16(qSafeDivide(1, topRightSlope)); - const Q16Dot16 invBottomLeftSlopeFP = FloatToQ16Dot16(1 / bottomLeftSlope); - const Q16Dot16 invBottomRightSlopeFP = FloatToQ16Dot16(1 / bottomRightSlope); + const Q16Dot16 invBottomLeftSlopeFP = qSafeFloatToQ16Dot16(qSafeDivide(1, bottomLeftSlope)); + const Q16Dot16 invBottomRightSlopeFP = qSafeFloatToQ16Dot16(qSafeDivide(1, bottomRightSlope)); if (d->antialiased) { const Q16Dot16 iTopFP = IntToQ16Dot16(int(topBound)); @@ -1137,10 +1166,10 @@ void QRasterizer::rasterizeLine(const QPointF &a, const QPointF &b, qreal width, int iBottom = bottom.y() < 0.5f? -1 : int(bottom.y() - 0.5f); int iMiddle = qMin(iLeft, iRight); - Q16Dot16 leftIntersectAf = FloatToQ16Dot16(top.x() + 0.5f + (iTop + 0.5f - top.y()) * topLeftSlope); - Q16Dot16 leftIntersectBf = FloatToQ16Dot16(left.x() + 0.5f + (iLeft + 1.5f - left.y()) * bottomLeftSlope); - Q16Dot16 rightIntersectAf = FloatToQ16Dot16(top.x() - 0.5f + (iTop + 0.5f - top.y()) * topRightSlope); - Q16Dot16 rightIntersectBf = FloatToQ16Dot16(right.x() - 0.5f + (iRight + 1.5f - right.y()) * bottomRightSlope); + Q16Dot16 leftIntersectAf = qSafeFloatToQ16Dot16(top.x() + 0.5f + (iTop + 0.5f - top.y()) * topLeftSlope); + Q16Dot16 leftIntersectBf = qSafeFloatToQ16Dot16(left.x() + 0.5f + (iLeft + 1.5f - left.y()) * bottomLeftSlope); + Q16Dot16 rightIntersectAf = qSafeFloatToQ16Dot16(top.x() - 0.5f + (iTop + 0.5f - top.y()) * topRightSlope); + Q16Dot16 rightIntersectBf = qSafeFloatToQ16Dot16(right.x() - 0.5f + (iRight + 1.5f - right.y()) * bottomRightSlope); int ny; int y = iTop; -- cgit v1.2.3