diff options
author | Edward Welbourne <edward.welbourne@qt.io> | 2020-09-09 14:59:32 +0200 |
---|---|---|
committer | Edward Welbourne <edward.welbourne@qt.io> | 2020-10-27 16:21:37 +0200 |
commit | 36cc28470f6573998dccd8d3d873a4a97fd94323 (patch) | |
tree | fe2807c3a2e3273965d09a2fba1de024d4654e0d /tests | |
parent | a6699dd0df0be39fc98a54642ac320e1d7a611d2 (diff) |
Deal with {und,ov}erflow issues in QLine's length handling
Use std::hypot() instead of sqrt() of a sum of squares.
This ensures length() can't be zero when isNull() is false.
Use length() in QLine::setLength() rather than duplicating that.
Clarify and expand some documentation; isNull() never said what
constituted validity, nor did unitVector() mention that is should not
be used on a line for which isNull() is true. Make clear that lines of
denormal length cannot be rescaled accurately.
Given that we use fuzzy comparison to determine equality of
end-points, isNull() can be false for a line with displacements less
than sqrt(numeric_limits<qreal>::denorm_min()) between the coordinates
of its end-points (as long as these are not much bigger); squaring
these would give zero, hence a zero length, where using hypot() avoids
the underflow and gives a non-zero length. Having a zero length for a
line with isNull() false would lead to problems in setLength(), which
uses an isNull() pre-test, protecting a call to unitVector().
(It was already possible for a null line to have non-zero length; this
now arises in more cases.)
Reworked QLine::setLength() to allow for the possibility that the unit
vector it computes as transient may not have length exactly one.
Add tests against {ov,und}erflow and divide-by-zero problems in QLine.
Picked version for 5.12 needed to adapt the test to simulate 5.15 and
later's QCOMPARE(act, exp) effectively testing qFuzzyIsNull(exp) ?
qFuzzyIsNull(act) : qFuzzyCompare(act, exp) where 5.12 just uses plain
qFuzzyCompare().
Change-Id: I7b71d66b872ccc08a64e941acd36b45b0ea15fab
Reviewed-by: Sze Howe Koh <szehowe.koh@gmail.com>
(cherry picked from commit 1c591fd9246ca776304a3c370dd2578bd886feac)
Reviewed-by: Paul Wicking <paul.wicking@qt.io>
Reviewed-by: Thiago Macieira <thiago.macieira@intel.com>
Diffstat (limited to 'tests')
-rw-r--r-- | tests/auto/corelib/tools/qline/tst_qline.cpp | 58 |
1 files changed, 45 insertions, 13 deletions
diff --git a/tests/auto/corelib/tools/qline/tst_qline.cpp b/tests/auto/corelib/tools/qline/tst_qline.cpp index ae65d8f697..21dc8b9434 100644 --- a/tests/auto/corelib/tools/qline/tst_qline.cpp +++ b/tests/auto/corelib/tools/qline/tst_qline.cpp @@ -1,6 +1,6 @@ /**************************************************************************** ** -** Copyright (C) 2016 The Qt Company Ltd. +** Copyright (C) 2020 The Qt Company Ltd. ** Contact: https://www.qt.io/licensing/ ** ** This file is part of the test suite of the Qt Toolkit. @@ -225,10 +225,12 @@ void tst_QLine::testLength_data() QTest::addColumn<double>("vx"); QTest::addColumn<double>("vy"); - QTest::newRow("[1,0]*2") << 0.0 << 0.0 << 1.0 << 0.0 << 1.0 << 2.0 << 2.0 << 0.0; - QTest::newRow("[0,1]*2") << 0.0 << 0.0 << 0.0 << 1.0 << 1.0 << 2.0 << 0.0 << 2.0; - QTest::newRow("[-1,0]*2") << 0.0 << 0.0 << -1.0 << 0.0 << 1.0 << 2.0 << -2.0 << 0.0; - QTest::newRow("[0,-1]*2") << 0.0 << 0.0 << 0.0 << -1.0 << 1.0 << 2.0 << 0.0 << -2.0; + // Test name: [dx,dy]->|lenToSet| (x1,x2) + // with the last part omitted if (0,0) + QTest::newRow("[1,0]->|2|") << 0.0 << 0.0 << 1.0 << 0.0 << 1.0 << 2.0 << 2.0 << 0.0; + QTest::newRow("[0,1]->|2|") << 0.0 << 0.0 << 0.0 << 1.0 << 1.0 << 2.0 << 0.0 << 2.0; + QTest::newRow("[-1,0]->|2|") << 0.0 << 0.0 << -1.0 << 0.0 << 1.0 << 2.0 << -2.0 << 0.0; + QTest::newRow("[0,-1]->|2|") << 0.0 << 0.0 << 0.0 << -1.0 << 1.0 << 2.0 << 0.0 << -2.0; QTest::newRow("[1,1]->|1|") << 0.0 << 0.0 << 1.0 << 1.0 << double(SQRT2) << 1.0 << double(UNITX_45) << double(UNITX_45); QTest::newRow("[-1,1]->|1|") << 0.0 << 0.0 << -1.0 << 1.0 @@ -237,10 +239,10 @@ void tst_QLine::testLength_data() << double(SQRT2) << 1.0 << double(UNITX_45) << double(-UNITX_45); QTest::newRow("[-1,-1]->|1|") << 0.0 << 0.0 << -1.0 << -1.0 << double(SQRT2) << 1.0 << double(-UNITX_45) << double(-UNITX_45); - QTest::newRow("[1,0]*2 (2,2)") << 2.0 << 2.0 << 3.0 << 2.0 << 1.0 << 2.0 << 2.0 << 0.0; - QTest::newRow("[0,1]*2 (2,2)") << 2.0 << 2.0 << 2.0 << 3.0 << 1.0 << 2.0 << 0.0 << 2.0; - QTest::newRow("[-1,0]*2 (2,2)") << 2.0 << 2.0 << 1.0 << 2.0 << 1.0 << 2.0 << -2.0 << 0.0; - QTest::newRow("[0,-1]*2 (2,2)") << 2.0 << 2.0 << 2.0 << 1.0 << 1.0 << 2.0 << 0.0 << -2.0; + QTest::newRow("[1,0]->|2| (2,2)") << 2.0 << 2.0 << 3.0 << 2.0 << 1.0 << 2.0 << 2.0 << 0.0; + QTest::newRow("[0,1]->|2| (2,2)") << 2.0 << 2.0 << 2.0 << 3.0 << 1.0 << 2.0 << 0.0 << 2.0; + QTest::newRow("[-1,0]->|2| (2,2)") << 2.0 << 2.0 << 1.0 << 2.0 << 1.0 << 2.0 << -2.0 << 0.0; + QTest::newRow("[0,-1]->|2| (2,2)") << 2.0 << 2.0 << 2.0 << 1.0 << 1.0 << 2.0 << 0.0 << -2.0; QTest::newRow("[1,1]->|1| (2,2)") << 2.0 << 2.0 << 3.0 << 3.0 << double(SQRT2) << 1.0 << double(UNITX_45) << double(UNITX_45); QTest::newRow("[-1,1]->|1| (2,2)") << 2.0 << 2.0 << 1.0 << 3.0 @@ -249,6 +251,20 @@ void tst_QLine::testLength_data() << double(SQRT2) << 1.0 << double(UNITX_45) << double(-UNITX_45); QTest::newRow("[-1,-1]->|1| (2,2)") << 2.0 << 2.0 << 1.0 << 1.0 << double(SQRT2) << 1.0 << double(-UNITX_45) << double(-UNITX_45); + const double small = qSqrt(std::numeric_limits<qreal>::denorm_min()) / 8; + QTest::newRow("[small,small]->|2| (-small/2,-small/2)") + << -(small * .5) << -(small * .5) << (small * .5) << (small * .5) + << (small * M_SQRT2) << (2 * M_SQRT2) << 2.0 << 2.0; + const double tiny = std::numeric_limits<qreal>::min() / 2; + QTest::newRow("[tiny,tiny]->|2| (-tiny/2,-tiny/2)") + << -(tiny * .5) << -(tiny * .5) << (tiny * .5) << (tiny * .5) + << (tiny * M_SQRT2) << (2 * M_SQRT2) << 2.0 << 2.0; + QTest::newRow("[1+3e-13,1+4e-13]|1895| (1, 1)") + << 1.0 << 1.0 << (1 + 3e-13) << (1 + 4e-13) // isNull(), so ignores setLength() + << 5e-13 << 1895.0 << 3e-13 << 4e-13; + QTest::newRow("[4e-323,5e-324]|1892|") // Unavoidable underflow: denormals + << 0.0 << 0.0 << 4e-323 << 5e-324 + << 4e-323 << 1892.0 << 4e-323 << 5e-324; // vx, vy values ignored } void tst_QLine::testLength() @@ -263,12 +279,28 @@ void tst_QLine::testLength() QFETCH(double, vy); QLineF l(x1, y1, x2, y2); - QCOMPARE(l.length(), qreal(length)); + const bool wasNull = l.isNull(); + if (!wasNull) + QCOMPARE(l.length(), qreal(length)); l.setLength(lengthToSet); - QCOMPARE(l.length(), qreal(lengthToSet)); - QCOMPARE(l.dx(), qreal(vx)); - QCOMPARE(l.dy(), qreal(vy)); + if (!wasNull) + QCOMPARE(l.length(), qreal(lengthToSet)); + else if (qFuzzyIsNull(qreal(length))) + QVERIFY(qFuzzyIsNull(l.length())); + else + QCOMPARE(l.length(), qreal(length)); + // Scaling tiny values up to big can be imprecise: don't try to test vx, vy + if (wasNull || !qFuzzyIsNull(length)) { + if (qFuzzyIsNull(qreal(vx))) + QVERIFY(qFuzzyIsNull(l.dx())); + else + QCOMPARE(l.dx(), qreal(vx)); + if (qFuzzyIsNull(qreal(vy))) + QVERIFY(qFuzzyIsNull(l.dy())); + else + QCOMPARE(l.dy(), qreal(vy)); + } } void tst_QLine::testCenter() |