QQuaternion: long live Axes / toAxes()

Compilers hate out parameters, so provide a replacement for getAxes(),
toAxes(), that returns the result in a struct Axes { x, y, z } instead.

Then make getAxes() an inline wrapper around a toAxes() call, porting
from Q_ASSERT(x && y && z) to Q_PRE(x); Q_PRE(y); Q_PRE(z); as a
drive-by. The separation gives a more detailed error when triggered,
and produces a shorter assertion string.

Add tests, naturally, and port getAxes() calls that don't test
getAxes() to the new function.

There appear to be no other in-tree users that could be ported.

For symmetry reasons, also add a fromAxes(Axes) overload. Take the
argument by value, to avoid the compiler having to deal with aliasing
analysis. At worst, pass-by-value is like pass-by-cref, and whether
or not the extra copy is added or, since C++17, elided, depends on the
specific call. Suppress Clazy's schizophrenic warning, which complains
that we don't take (QVector3D, QVector3D, QVector3D) by value, but
also if we take struct {QVector x,y,z} by value.

[ChangeLog][QtGui][QQuaternion] Added toAxes(), a getAxes()
replacement.

Task-number: QTBUG-138199
Change-Id: Ie26e16528dc06806e59e54eff2d656a33c322bad
Reviewed-by: Volker Hilsheimer <[email protected]>

1 files changed, 13 insertions, 10 deletions

diff --git a/tests/auto/gui/math3d/qquaternion/tst_qquaternion.cpp b/tests/auto/gui/math3d/qquaternion/tst_qquaternion.cpp
index bd4a230b78a..d4dc6544a0e 100644
--- a/tests/auto/gui/math3d/qquaternion/tst_qquaternion.cpp
+++ b/tests/auto/gui/math3d/qquaternion/tst_qquaternion.cpp
@@ -894,6 +894,13 @@ void tst_QQuaternion::fromAxes()
 
     QQuaternion result = QQuaternion::fromAxisAndAngle(QVector3D(x1, y1, z1), angle);
 
+    {
+        const auto axes = result.toAxes();
+        QVERIFY(myFuzzyCompare(axes.x, xAxis));
+        QVERIFY(myFuzzyCompare(axes.y, yAxis));
+        QVERIFY(myFuzzyCompare(axes.z, zAxis));
+    }
+
     QVector3D axes[3];
     result.getAxes(&axes[0], &axes[1], &axes[2]);
     QVERIFY(myFuzzyCompare(axes[0], xAxis));
@@ -985,8 +992,7 @@ void tst_QQuaternion::fromDirection_data()
 
     // othonormal up and dir
     for (QQuaternion q : orientations) {
-        QVector3D xAxis, yAxis, zAxis;
-        q.getAxes(&xAxis, &yAxis, &zAxis);
+        const auto [xAxis, yAxis, zAxis] = q.toAxes();
 
         QTest::addRow("ortho dirs: (%.1f,%.1f,%.1f), (%.1f,%.1f,%.1f), (%.1f,%.1f,%.1f)",
                       xAxis.x(), xAxis.y(), xAxis.z(),
@@ -1007,8 +1013,7 @@ void tst_QQuaternion::fromDirection_data()
 
     // invalid up
     for (QQuaternion q : orientations) {
-        QVector3D xAxis, yAxis, zAxis;
-        q.getAxes(&xAxis, &yAxis, &zAxis);
+        const auto [xAxis, yAxis, zAxis] = q.toAxes();
 
         QTest::addRow("bad dirs: (%.1f,%.1f,%.1f), (%.1f,%.1f,%.1f), (%.1f,%.1f,%.1f)",
                       xAxis.x(), xAxis.y(), xAxis.z(),
@@ -1029,16 +1034,14 @@ void tst_QQuaternion::fromDirection()
     QQuaternion result = QQuaternion::fromDirection(direction, up);
     QVERIFY(myFuzzyCompare(result, result.normalized()));
 
-    QVector3D xAxis, yAxis, zAxis;
-    result.getAxes(&xAxis, &yAxis, &zAxis);
-
-    QVERIFY(myFuzzyCompare(zAxis, expectedZ));
+    const auto axes = result.toAxes();
 
+    QVERIFY(myFuzzyCompare(axes.z, expectedZ));
 
     const QVector3D expectedX = QVector3D::crossProduct(expectedY, expectedZ);
     if (!qFuzzyIsNull(expectedX.lengthSquared())) {
-        QVERIFY(myFuzzyCompare(xAxis, expectedX));
-        QVERIFY(myFuzzyCompare(yAxis, expectedY));
+        QVERIFY(myFuzzyCompare(axes.x, expectedX));
+        QVERIFY(myFuzzyCompare(axes.y, expectedY));
     }
 }