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>

1 files changed, 3 insertions, 6 deletions

diff --git a/examples/widgets/effects/blurpicker/blurpicker.cpp b/examples/widgets/effects/blurpicker/blurpicker.cpp
index 43823bed30..a00af2144a 100644
--- a/examples/widgets/effects/blurpicker/blurpicker.cpp
+++ b/examples/widgets/effects/blurpicker/blurpicker.cpp
@@ -52,13 +52,9 @@
 
 #include <QtWidgets>
 #include <QtCore/qmath.h>
-
+#include <qmath.h>
 #include "blureffect.h"
 
-#ifndef M_PI
-#define M_PI 3.14159265358979323846
-#endif
-
 BlurPicker::BlurPicker(QWidget *parent): QGraphicsView(parent), m_index(0.0), m_animation(this, "index")
 {
     setBackgroundBrush(QPixmap(":/images/background.jpg"));
@@ -84,9 +80,10 @@ void BlurPicker::setIndex(qreal index)
     m_index = index;
 
     qreal baseline = 0;
+    const qreal iconAngle = 2 * M_PI / m_icons.count();
     for (int i = 0; i < m_icons.count(); ++i) {
         QGraphicsItem *icon = m_icons[i];
-        qreal a = ((i + m_index) * 2 * M_PI) / m_icons.count();
+        qreal a = (i + m_index) * iconAngle;
         qreal xs = 170 * qSin(a);
         qreal ys = 100 * qCos(a);
         QPointF pos(xs, ys);