Use qRadiansToDegrees() and qDegreesToRadians() more widely

Especially in examples, where we should show off our convenience
functions, prefer calling these functions over doing arithmetic with
M_PI (or approximations thereto) and 180 (give or take simple
factors).  This incidentally documents what's going on, just by the
name of the function used (and reveals at least one place where
variables were misnamed; the return from atan is in radians, *not*
degrees).

Task-number: QTBUG-58083
Change-Id: I6e5d66721cafab423378f970af525400423e971e
Reviewed-by: Jüri Valdmann <juri.valdmann@qt.io>
Reviewed-by: Allan Sandfeld Jensen <allan.jensen@qt.io>
Reviewed-by: Marc Mutz <marc.mutz@kdab.com>

examples/dbus/remotecontrolledcar/car/car.cpp

@@ -50,9 +50,7 @@
 
 #include "car.h"
 #include <QtWidgets/QtWidgets>
-#include <math.h>
+#include <qmath.h>
-
-static const double Pi = 3.14159265358979323846264338327950288419717;
 
 QRectF Car::boundingRect() const
 {
@@ -135,10 +133,10 @@ void Car::timerEvent(QTimerEvent *event)
     Q_UNUSED(event);
 
     const qreal axelDistance = 54;
-    qreal wheelsAngleRads = (wheelsAngle * Pi) / 180;
+    qreal wheelsAngleRads = qDegreesToRadians(wheelsAngle);
     qreal turnDistance = ::cos(wheelsAngleRads) * axelDistance * 2;
     qreal turnRateRads = wheelsAngleRads / turnDistance;  // rough estimate
-    qreal turnRate = (turnRateRads * 180) / Pi;
+    qreal turnRate = qRadiansToDegrees(turnRateRads);
     qreal rotation = speed * turnRate;
 
     setTransform(QTransform().rotate(rotation), true);

examples/embedded/lightmaps/slippymap.cpp

@@ -48,15 +48,10 @@
 **
 ****************************************************************************/
 
-#include <math.h>
-
 #include <QtWidgets>
 #include <QtNetwork>
 #include "slippymap.h"
-
+#include "qmath.h"
-#ifndef M_PI
-#define M_PI 3.14159265358979323846
-#endif
 
 uint qHash(const QPoint& p)
 {
@@ -68,10 +63,10 @@ const int tdim = 256;
 
 QPointF tileForCoordinate(qreal lat, qreal lng, int zoom)
 {
+    qreal radianLat = qDegreesToRadians(lat);
     qreal zn = static_cast<qreal>(1 << zoom);
     qreal tx = (lng + 180.0) / 360.0;
-    qreal ty = (1.0 - log(tan(lat * M_PI / 180.0) +
+    qreal ty = 0.5 - log(tan(radianLat) + 1.0 / cos(radianLat)) / M_PI / 2.0;
-                          1.0 / cos(lat * M_PI / 180.0)) / M_PI) / 2.0;
     return QPointF(tx * zn, ty * zn);
 }
 
@@ -86,8 +81,7 @@ qreal latitudeFromTile(qreal ty, int zoom)
 {
     qreal zn = static_cast<qreal>(1 << zoom);
     qreal n = M_PI - 2 * M_PI * ty / zn;
-    qreal lng = 180.0 / M_PI * atan(0.5 * (exp(n) - exp(-n)));
+    return qRadiansToDegrees(atan(0.5 * (exp(n) - exp(-n))));
-    return lng;
 }
 
 

examples/widgets/animation/stickman/stickman.cpp

@@ -53,13 +53,7 @@
 
 #include <QPainter>
 #include <QTimer>
-
+#include <qmath.h>
-#define _USE_MATH_DEFINES
-#include <math.h>
-
-#ifndef M_PI
-#define M_PI 3.14159265358979323846
-#endif
 
 static const qreal Coords[NodeCount * 2] = {
     0.0, -150.0, // head, #0
@@ -300,7 +294,7 @@ void StickMan::paint(QPainter *painter, const QStyleOptionGraphicsItem *, QWidge
             QPointF dist = node2->pos() - node1->pos();
 
             qreal sinAngle = dist.x() / sqrt(pow(dist.x(), 2) + pow(dist.y(), 2));
-            qreal angle = asin(sinAngle) * 180.0 / M_PI;
+            qreal angle = qRadiansToDegrees(asin(sinAngle));
 
             QPointF headPos = node1->pos();
             painter->translate(headPos);

examples/widgets/effects/lighting/lighting.cpp

@@ -49,14 +49,9 @@
 ****************************************************************************/
 
 #include "lighting.h"
-
 #include <QtWidgets>
 #include <QtCore/qmath.h>
 
-#ifndef M_PI
-#define M_PI 3.14159265358979323846
-#endif
-
 Lighting::Lighting(QWidget *parent): QGraphicsView(parent), angle(0.0)
 {
     setScene(&m_scene);
@@ -120,7 +115,7 @@ void Lighting::setupScene()
 
 void Lighting::animate()
 {
-    angle += (M_PI / 30);
+    angle += qDegreesToRadians(qreal(6));
     qreal xs = 200 * qSin(angle) - 40 + 25;
     qreal ys = 200 * qCos(angle) - 40 + 25;
     m_lightSource->setPos(xs, ys);

examples/widgets/graphicsview/boxes/glbuffers.cpp

@@ -50,11 +50,11 @@
 
 #include "glbuffers.h"
 #include <QtGui/qmatrix4x4.h>
-
+#include <QtCore/qmath.h>
 
 void qgluPerspective(GLdouble fovy, GLdouble aspect, GLdouble zNear, GLdouble zFar)
 {
-    const GLdouble ymax = zNear * tan(fovy * M_PI / 360.0);
+    const GLdouble ymax = zNear * tan(qDegreesToRadians(fovy) / 2.0);
     const GLdouble ymin = -ymax;
     const GLdouble xmin = ymin * aspect;
     const GLdouble xmax = ymax * aspect;

examples/widgets/graphicsview/boxes/trackball.cpp

@@ -50,6 +50,7 @@
 
 #include "trackball.h"
 #include "scene.h"
+#include <qmath.h>
 #include <cmath>
 
 //============================================================================//
@@ -101,10 +102,11 @@ void TrackBall::move(const QPointF& p, const QQuaternion &transformation)
     case Plane:
         {
             QLineF delta(m_lastPos, p);
-            m_angularVelocity = 180*delta.length() / (PI*msecs);
+            const float angleDelta = qRadiansToDegrees(float(delta.length()));
+            m_angularVelocity = angleDelta / msecs;
             m_axis = QVector3D(-delta.dy(), delta.dx(), 0.0f).normalized();
             m_axis = transformation.rotatedVector(m_axis);
-            m_rotation = QQuaternion::fromAxisAndAngle(m_axis, 180 / PI * delta.length()) * m_rotation;
+            m_rotation = QQuaternion::fromAxisAndAngle(m_axis, angleDelta) * m_rotation;
         }
         break;
     case Sphere:
@@ -124,7 +126,7 @@ void TrackBall::move(const QPointF& p, const QQuaternion &transformation)
                 currentPos3D.normalize();
 
             m_axis = QVector3D::crossProduct(lastPos3D, currentPos3D);
-            float angle = 180 / PI * std::asin(std::sqrt(QVector3D::dotProduct(m_axis, m_axis)));
+            float angle = qRadiansToDegrees(std::asin(std::sqrt(QVector3D::dotProduct(m_axis, m_axis))));
 
             m_angularVelocity = angle / msecs;
             m_axis.normalize();

examples/widgets/itemviews/chart/pieview.cpp

@@ -49,12 +49,8 @@
 ****************************************************************************/
 
 #include <QtWidgets>
+#include <qmath.h>
 #include <cmath>
-
-#ifndef M_PI
-#define M_PI 3.1415927
-#endif
-
 #include "pieview.h"
 
 PieView::PieView(QWidget *parent)
@@ -125,7 +121,7 @@ QModelIndex PieView::indexAt(const QPoint &point) const
             return QModelIndex();
 
         // Determine the angle of the point.
-        double angle = (180 / M_PI) * std::atan2(cy, cx);
+        double angle = qRadiansToDegrees(std::atan2(cy, cx));
         if (angle < 0)
             angle = 360 + angle;
 

src/gui/math3d/qmatrix4x4.cpp

@@ -1128,7 +1128,7 @@ void QMatrix4x4::rotate(float angle, float x, float y, float z)
         s = 0.0f;
         c = -1.0f;
     } else {
-        float a = angle * M_PI / 180.0f;
+        float a = qDegreesToRadians(angle);
         c = std::cos(a);
         s = std::sin(a);
     }
@@ -1237,7 +1237,7 @@ void QMatrix4x4::projectedRotate(float angle, float x, float y, float z)
         s = 0.0f;
         c = -1.0f;
     } else {
-        float a = angle * M_PI / 180.0f;
+        float a = qDegreesToRadians(angle);
         c = std::cos(a);
         s = std::sin(a);
     }
@@ -1496,7 +1496,7 @@ void QMatrix4x4::perspective(float verticalAngle, float aspectRatio, float nearP
 
     // Construct the projection.
     QMatrix4x4 m(1);
-    float radians = (verticalAngle / 2.0f) * M_PI / 180.0f;
+    float radians = qDegreesToRadians(verticalAngle / 2.0f);
     float sine = std::sin(radians);
     if (sine == 0.0f)
         return;

src/gui/math3d/qquaternion.cpp

@@ -408,7 +408,7 @@ QQuaternion QQuaternion::fromAxisAndAngle(const QVector3D& axis, float angle)
     // http://www.j3d.org/matrix_faq/matrfaq_latest.html#Q56
     // We normalize the result just in case the values are close
     // to zero, as suggested in the above FAQ.
-    float a = (angle / 2.0f) * M_PI / 180.0f;
+    float a = qDegreesToRadians(angle / 2.0f);
     float s = std::sin(a);
     float c = std::cos(a);
     QVector3D ax = axis.normalized();
@@ -467,7 +467,7 @@ QQuaternion QQuaternion::fromAxisAndAngle
         y /= length;
         z /= length;
     }
-    float a = (angle / 2.0f) * M_PI / 180.0f;
+    float a = qDegreesToRadians(angle / 2.0f);
     float s = std::sin(a);
     float c = std::cos(a);
     return QQuaternion(c, x * s, y * s, z * s).normalized();

src/gui/text/qdistancefield.cpp

@@ -516,7 +516,7 @@ static void makeDistanceField(QDistanceFieldData *data, const QPainterPath &path
     for (int i = 0; i < imgWidth * imgHeight; ++i)
         bits[i] = exteriorColor;
 
-    const qreal angleStep = qreal(15 * 3.141592653589793238 / 180);
+    const qreal angleStep = qDegreesToRadians(qreal(15));
     const QPoint rotation(qRound(qCos(angleStep) * 0x4000),
                           qRound(qSin(angleStep) * 0x4000)); // 2:14 signed
 

src/plugins/generic/tuiotouch/qtuiohandler.cpp

@@ -523,7 +523,7 @@ QWindowSystemInterface::TouchPoint QTuioHandler::tokenToTouchPoint(const QTuioTo
     QPointF delta = relPos - relPos.toPoint();
     tp.area.moveCenter(win->mapToGlobal(relPos.toPoint()) + delta);
     tp.velocity = QVector2D(win->size().width() * tc.vx(), win->size().height() * tc.vy());
-    tp.rotation = tc.angle() * 180.0 / M_PI; // convert radians to degrees
+    tp.rotation = qRadiansToDegrees(tc.angle());
     return tp;
 }
 

src/plugins/platforms/android/androidjniinput.cpp

@@ -50,6 +50,7 @@
 
 #include <QGuiApplication>
 #include <QDebug>
+#include <QtMath>
 
 QT_BEGIN_NAMESPACE
 
@@ -251,7 +252,7 @@ namespace QtAndroidInput
         QWindowSystemInterface::TouchPoint touchPoint;
         touchPoint.id = id;
         touchPoint.pressure = pressure;
-        touchPoint.rotation = rotation * 180 / M_PI;
+        touchPoint.rotation = qRadiansToDegrees(rotation);
         touchPoint.normalPosition = QPointF(double(x / dw), double(y / dh));
         touchPoint.state = state;
         touchPoint.area = QRectF(x - double(minor),

src/plugins/platforms/windows/qwindowstabletsupport.cpp

@@ -463,13 +463,13 @@ bool QWindowsTabletSupport::translateTabletPacketEvent()
             // Z = sin(altitude)
             // X Tilt = arctan(X / Z)
             // Y Tilt = arctan(Y / Z)
-            const double radAzim = (packet.pkOrientation.orAzimuth / 10.0) * (M_PI / 180);
+            const double radAzim = qDegreesToRadians(packet.pkOrientation.orAzimuth / 10.0);
-            const double tanAlt = std::tan((std::abs(packet.pkOrientation.orAltitude / 10.0)) * (M_PI / 180));
+            const double tanAlt = std::tan(qDegreesToRadians(std::abs(packet.pkOrientation.orAltitude / 10.0)));
 
             const double degX = std::atan(std::sin(radAzim) / tanAlt);
             const double degY = std::atan(std::cos(radAzim) / tanAlt);
-            tiltX = int(degX * (180 / M_PI));
+            tiltX = int(qRadiansToDegrees(degX));
-            tiltY = int(-degY * (180 / M_PI));
+            tiltY = int(qRadiansToDegrees(-degY));
             rotation = 360.0 - (packet.pkOrientation.orTwist / 10.0);
             if (rotation > 180.0)
                 rotation -= 360.0;

tests/auto/gui/math3d/qmatrixnxn/tst_qmatrixnxn.cpp

@@ -2278,8 +2278,8 @@ void tst_QMatrixNxN::rotate4x4_data()
     float y = 2.0f;
     float z = -6.0f;
     float angle = -45.0f;
-    float c = std::cos(angle * M_PI / 180.0f);
+    float c = std::cos(qDegreesToRadians(angle));
-    float s = std::sin(angle * M_PI / 180.0f);
+    float s = std::sin(qDegreesToRadians(angle));
     float len = std::sqrt(x * x + y * y + z * z);
     float xu = x / len;
     float yu = y / len;

tests/auto/gui/math3d/qquaternion/tst_qquaternion.cpp

@@ -815,7 +815,7 @@ void tst_QQuaternion::fromAxisAndAngle()
     // http://www.j3d.org/matrix_faq/matrfaq_latest.html#Q56
     // to calculate the answer we expect to get.
     QVector3D vector = QVector3D(x1, y1, z1).normalized();
-    const float a = (angle * M_PI / 180.0) / 2.0;
+    const float a = qDegreesToRadians(angle) / 2.0;
     const float sin_a = std::sin(a);
     const float cos_a = std::cos(a);
     QQuaternion result(cos_a,

tests/auto/gui/painting/qwmatrix/tst_qwmatrix.cpp

@@ -114,12 +114,8 @@ void tst_QWMatrix::mapping_data()
                                 << QRect( 0, 0, 30, 40 )
                                 << QPolygon( QRect( -300, -400, 300, 400 ) );
 
-#if defined(Q_OS_WIN) && !defined(M_PI)
-#define M_PI 3.14159265897932384626433832795f
-#endif
-
     const auto rotate = [](qreal degrees) {
-        const qreal rad = M_PI * degrees / 180.;
+        const qreal rad = qDegreesToRadians(degrees);
         return QMatrix(std::cos(rad), -std::sin(rad),
                        std::sin(rad),  std::cos(rad), 0, 0);
     };
@@ -140,7 +136,7 @@ void tst_QWMatrix::mapping_data()
 
 #if 0
     const auto rotScale = [](qreal degrees, qreal scale) {
-        const qreal rad = M_PI * degrees / 180.;
+        const qreal rad = qDegreesToRadians(degrees);
         return QMatrix(scale * std::cos(rad), -scale * std::sin(rad),
                        scale * std::sin(rad),  scale * std::cos(rad), 0, 0);
     };

tests/benchmarks/gui/painting/qpainter/tst_qpainter.cpp

@@ -33,10 +33,7 @@
 #include <QImage>
 #include <QPaintEngine>
 #include <QTileRules>
-#include <math.h>
+#include <qmath.h>
-#ifndef M_PI
-#define M_PI 3.14159265358979323846
-#endif
 
 #include <private/qpixmap_raster_p.h>
 
@@ -1232,7 +1229,7 @@ QTransform tst_QPainter::transformForAngle(qreal angle)
     QTransform rotTrans2;
     rotTrans2.translate(40, 0);
 
-    qreal rad = angle * 2. * M_PI / 360.;
+    qreal rad = qDegreesToRadians(angle);
     qreal c = ::cos(rad);
     qreal s = ::sin(rad);