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, 5 insertions, 8 deletions

diff --git a/examples/opengl/legacy/pbuffers2/glwidget.cpp b/examples/opengl/legacy/pbuffers2/glwidget.cpp
index c99f9e40fa..447461dbb3 100644
--- a/examples/opengl/legacy/pbuffers2/glwidget.cpp
+++ b/examples/opengl/legacy/pbuffers2/glwidget.cpp
@@ -49,10 +49,9 @@
 ****************************************************************************/
 
 #include <QtGui/QImage>
+#include <qmath.h>
 #include "glwidget.h"
 
-#include <math.h>
-
 #ifndef GL_MULTISAMPLE
 #define GL_MULTISAMPLE  0x809D
 #endif
@@ -291,8 +290,6 @@ void GLWidget::restoreGLState()
     glPopAttrib();
 }
 
-#define PI 3.14159
-
 void GLWidget::timerEvent(QTimerEvent *)
 {
     if (QApplication::mouseButtons() != 0)
@@ -310,7 +307,7 @@ void GLWidget::timerEvent(QTimerEvent *)
     rot_x += 0.1f;
 
     int dx, dy; // disturbance point
-    float s, v, W, t;
+    float s, v, W;
     int i, j;
     static float wt[128][128];
     const int width = logo.width();
@@ -325,11 +322,11 @@ void GLWidget::timerEvent(QTimerEvent *)
         for ( j = 0; j < width; ++j) {
             s = sqrt((double) ((j - dx) * (j - dx) + (i - dy) * (i - dy)));
             wt[i][j] += 0.1f;
-            t = s / v;
+            const double angle = 2 * M_PI * W * (wt[i][j] + s / v);
             if (s != 0)
-                wave[i*width + j] = AMP * sin(2 * PI * W * (wt[i][j] + t)) / (0.2*(s + 2));
+                wave[i * width + j] = AMP * sin(angle) / (0.2 * (s + 2));
             else
-                wave[i*width + j] = AMP * sin(2 * PI * W * (wt[i][j] + t));
+                wave[i * width + j] = AMP * sin(angle);
         }
     }
 }