Removing accidental use of double instead of qreal from QLine

QLine contained a number of places where conversions and calculations
were done as double where qreal should have been used instead. This
is caused by the use of raw floating point literals. The fix is to
construct the literals as qreal. The angle conversions are simplified
to reduce the risk of a growing loss of precision from this change.

On Symbian, where qreal is float, this gives a 5-10% performance
improvement to the affected functions, as tested by a new benchmark
test. The auto tests pass, these contain precision tests which indicates
that there is no significant loss of precision with this change.

On Windows, where qreal is double, this has no significant effect on
performance.

Task-number: QTBUG-4894
Reviewed-by: Shane Kearns

1 files changed, 13 insertions, 8 deletions

diff --git a/src/corelib/tools/qline.cpp b/src/corelib/tools/qline.cpp
index 0f67652..9c7c243 100644
--- a/src/corelib/tools/qline.cpp
+++ b/src/corelib/tools/qline.cpp
@@ -302,10 +302,15 @@ QDataStream &operator>>(QDataStream &stream, QLine &line)
 
 #endif // QT_NO_DATASTREAM
 
+inline static qreal q_deg2rad(qreal x)
+{
+    return x * qreal(0.01745329251994329576923690768489);    /* pi/180 */
+}
 
-#ifndef M_2PI
-#define M_2PI 6.28318530717958647692528676655900576
-#endif
+inline static qreal q_rad2deg(qreal x)
+{
+    return x * qreal(57.295779513082320876798154814105);    /* 180/pi */
+}
 
 /*!
     \class QLineF
@@ -575,7 +580,7 @@ qreal QLineF::angle() const
     const qreal dx = pt2.x() - pt1.x();
     const qreal dy = pt2.y() - pt1.y();
 
-    const qreal theta = qAtan2(-dy, dx) * 360.0 / M_2PI;
+    const qreal theta = q_rad2deg(qAtan2(-dy, dx));
 
     const qreal theta_normalized = theta < 0 ? theta + 360 : theta;
 
@@ -599,7 +604,7 @@ qreal QLineF::angle() const
 */
 void QLineF::setAngle(qreal angle)
 {
-    const qreal angleR = angle * M_2PI / 360.0;
+    const qreal angleR = q_deg2rad(angle);
     const qreal l = length();
 
     const qreal dx = qCos(angleR) * l;
@@ -621,7 +626,7 @@ void QLineF::setAngle(qreal angle)
 */
 QLineF QLineF::fromPolar(qreal length, qreal angle)
 {
-    const qreal angleR = angle * M_2PI / 360.0;
+    const qreal angleR = q_deg2rad(angle);
     return QLineF(0, 0, qCos(angleR) * length, -qSin(angleR) * length);
 }
 
@@ -815,8 +820,8 @@ qreal QLineF::angle(const QLineF &l) const
     qreal cos_line = (dx()*l.dx() + dy()*l.dy()) / (length()*l.length());
     qreal rad = 0;
     // only accept cos_line in the range [-1,1], if it is outside, use 0 (we return 0 rather than PI for those cases)
-    if (cos_line >= -1.0 && cos_line <= 1.0) rad = qAcos( cos_line );
-    return rad * 360 / M_2PI;
+    if (cos_line >= qreal(-1.0) && cos_line <= qreal(1.0)) rad = qAcos( cos_line );
+    return q_rad2deg(rad);
 }