Be (somewhat more) consistent about the value of pi

Use M_PI (and friends), where possible, in favor of hand-coded
approximations of various (in)accuracies.  Where that's not available
(e.g. fragment shaders), use the same value that qmath.h uses for
M_PI, for consistency.  Replaced math.h with qmath.h in places that
defined a fall-back in case math.h omits it (it's not in the C++
standard, although M_PI is in POSIX); or removed this entirely where
it wasn't used.

Reworked some code to reduce the amount of arithmetic needed, in the
process; e.g. pulling common factors out of loops.  Revised an
example's doc to not waste time talking about using a six-sig-fig
value for pi (which we no longer do) - it really wasn't relevant, or
anything to be proud of; nor did the doc mention its later use.

Task-number: QTBUG-58083
Change-Id: I5a31e3a2b6a823b97a43209bed61a37b9aa6c05f
Reviewed-by: Thiago Macieira <thiago.macieira@intel.com>

2 files changed, 3 insertions, 4 deletions

diff --git a/examples/widgets/graphicsview/boxes/scene.cpp b/examples/widgets/graphicsview/boxes/scene.cpp
index 9ac429c667..31b9553c75 100644
--- a/examples/widgets/graphicsview/boxes/scene.cpp
+++ b/examples/widgets/graphicsview/boxes/scene.cpp
@@ -52,7 +52,7 @@
 #include "scene.h"
 #include <QtGui/qmatrix4x4.h>
 #include <QtGui/qvector3d.h>
-#include <cmath>
+#include <qmath.h>
 
 #include "3rdparty/fbm.h"
 
@@ -868,11 +868,12 @@ void Scene::renderCubemaps()
 
     QVector3D center;
 
+    const float eachAngle = 2 * M_PI / m_cubemaps.size();
     for (int i = m_frame % N; i < m_cubemaps.size(); i += N) {
         if (0 == m_cubemaps[i])
             continue;
 
-        float angle = 2.0f * PI * i / m_cubemaps.size();
+        float angle = i * eachAngle;
 
         center = m_trackBalls[1].rotation().rotatedVector(QVector3D(std::cos(angle), std::sin(angle), 0.0f));
 
diff --git a/examples/widgets/graphicsview/boxes/scene.h b/examples/widgets/graphicsview/boxes/scene.h
index a2ba1d0b5a..ccb6f368cd 100644
--- a/examples/widgets/graphicsview/boxes/scene.h
+++ b/examples/widgets/graphicsview/boxes/scene.h
@@ -63,8 +63,6 @@
 #include "glbuffers.h"
 #include "qtbox.h"
 
-#define PI 3.14159265358979
-
 QT_BEGIN_NAMESPACE
 class QMatrix4x4;
 QT_END_NAMESPACE