Use qRadiansToDegrees() and qDegreesToRadians() more widely

These document what the arithmetic is actually doing; and save us an
ad-hoc use of an approximate value for pi while we're about it.

Task-number: QTBUG-58083
Change-Id: I82c5502af724b33ec598c5a9da76537f93a95eac
Reviewed-by: Tomi Korpipää <tomi.korpipaa@qt.io>

5 files changed, 10 insertions, 13 deletions

diff --git a/examples/datavisualization/bars/graphmodifier.cpp b/examples/datavisualization/bars/graphmodifier.cpp
index 8ef1c536..a130b0ff 100644
--- a/examples/datavisualization/bars/graphmodifier.cpp
+++ b/examples/datavisualization/bars/graphmodifier.cpp
@@ -353,7 +353,7 @@ void GraphModifier::zoomToSelectedBar()
 
         // Rotate the camera so that it always points approximately to the graph center
         //! [15]
-        qreal endAngleX = qAtan(qreal(endTarget.z() / endTarget.x())) / M_PI * -180.0 + 90.0;
+        qreal endAngleX = 90.0 - qRadiansToDegrees(qAtan(qreal(endTarget.z() / endTarget.x())));
         if (endTarget.x() > 0.0f)
             endAngleX -= 180.0f;
         float barValue = m_graph->selectedSeries()->dataProxy()->itemAt(selectedBar.x(),
diff --git a/src/datavisualization/data/qbar3dseries.cpp b/src/datavisualization/data/qbar3dseries.cpp
index c338b859..e2be7cc9 100644
--- a/src/datavisualization/data/qbar3dseries.cpp
+++ b/src/datavisualization/data/qbar3dseries.cpp
@@ -246,7 +246,7 @@ QPoint QBar3DSeries::invalidSelectionPosition()
 
 static inline float quaternionAngle(const QQuaternion &rotation)
 {
-    return qAcos(rotation.scalar()) * 360.0f / M_PI;
+    return qRadiansToDegrees(qAcos(rotation.scalar())) * 2.f;
 }
 
 /*!
diff --git a/src/datavisualization/engine/surface3drenderer.cpp b/src/datavisualization/engine/surface3drenderer.cpp
index 9cfa0edc..fa8bae8e 100644
--- a/src/datavisualization/engine/surface3drenderer.cpp
+++ b/src/datavisualization/engine/surface3drenderer.cpp
@@ -1150,7 +1150,7 @@ void Surface3DRenderer::drawScene(GLuint defaultFboHandle)
             // Need to determine if camera is below graph top
             float distanceToCenter = activeCamera->position().length()
                     / activeCamera->zoomLevel() / m_autoScaleAdjustment * 100.0f;
-            qreal cameraAngle = qreal(activeCamera->yRotation()) / 180.0 * M_PI;
+            qreal cameraAngle = qDegreesToRadians(qreal(activeCamera->yRotation()));
             float cameraYPos = float(qSin(cameraAngle)) * distanceToCenter;
             m_yFlippedForGrid = cameraYPos < (m_scaleYWithBackground - m_oldCameraTarget.y());
         } else if (m_useOrthoProjection && activeCamera->yRotation() == 0.0f) {
diff --git a/tests/manual/directional/scatterdatamodifier.cpp b/tests/manual/directional/scatterdatamodifier.cpp
index a11278fa..2a98625d 100644
--- a/tests/manual/directional/scatterdatamodifier.cpp
+++ b/tests/manual/directional/scatterdatamodifier.cpp
@@ -42,7 +42,6 @@ using namespace QtDataVisualization;
 const int numberOfCols = 8;
 const int numberOfRows = 8;
 const float limit = 8.0f;
-const float PI = 3.14159f;
 #define HEDGEHOG
 
 ScatterDataModifier::ScatterDataModifier(Q3DScatter *scatter)
@@ -97,18 +96,18 @@ void ScatterDataModifier::addData()
 
     for (float i = 0; i < numberOfRows; i++) {
         float latAngle = float(i) * latAngleStep + 40.0f;
-        float radius = qSin(latAngle * PI / 180.0f) * limit;
-        float y = qCos(latAngle * PI / 180.0f) * 1.0f;
+        float radius = qSin(qDegreesToRadians(latAngle)) * limit;
+        float y = qCos(qDegreesToRadians(latAngle)) * 1.0f;
 #ifdef HEDGEHOG
-        float angleZ = (qAtan((y * limit / 2.0f) / radius) * 180.0f / PI);
+        float angleZ = qRadiansToDegrees(qAtan((y * limit / 2.0f) / radius));
         QQuaternion rotationZ = QQuaternion::fromAxisAndAngle(QVector3D(0.0f, 0.0f, 1.0f), angleZ - 90.0f);
 #endif
         for (float j = 0; j < numberOfCols; j++) {
             float angle = float(j) * angleStep;
-            float x = qCos(angle * PI / 180.0f) * radius;
-            float z = qSin(angle * PI / 180.0f) * radius;
+            float x = qCos(qDegreesToRadians(angle)) * radius;
+            float z = qSin(qDegreesToRadians(angle)) * radius;
 
-            float angleY = (qAtan(z / x) * 180.0f / PI);
+            float angleY = qRadiansToDegrees(qAtan(z / x));
             if (x < 0)
                 angleY = 180.0f + angleY;
             if (x > 0 && z < 0)
diff --git a/tests/manual/galaxy/star.cpp b/tests/manual/galaxy/star.cpp
index 1513c93b..ca6b66f0 100644
--- a/tests/manual/galaxy/star.cpp
+++ b/tests/manual/galaxy/star.cpp
@@ -31,8 +31,6 @@
 
 #include <QtCore/qmath.h>
 
-static const double DEG_TO_RAD = M_PI / 180.0;
-
 Star::Star()
     : m_theta(0),
       m_a(0),
@@ -49,7 +47,7 @@ const void Star::calcXY()
     const QVector2D &p = m_center;
 
     qreal beta  = -m_angle;
-    qreal alpha = theta * DEG_TO_RAD;
+    qreal alpha = qDegreesToRadians(theta);
 
     // temporaries to save cpu time
     qreal cosalpha = qCos(alpha);