Make gui/math3d classes use float rather than qreal

This corrects the mismatch between using floats for internal storage
and qreal in the API of QVector*D which leads to lots of implicit
casts between double and float.

This change also stops users from being surprised by the loss of
precision when using these classes on desktop platforms and removes
the need for the private constructors taking a dummy int as the final
argument.

The QMatrix4x4 and QQuaternion classes have been changed to use float
for their internal storage since these are meant to be used in
conjunction with the QVector*D classes. This is to prevent unexpected
loss of precision and to improve performance.

The on-disk format has also been changed from double to float thereby
reducing the storage required when streaming vectors and matrices. This
is potentially a large saving when working with complex 3D meshes etc.

This also has a significant performance improvement when passing
matrices to QOpenGLShaderProgram (and QGLShaderProgram) as we no
longer have to iterate and convert the data to floats. This is
an operation that could easily be needed many times per frame.

This change also opens the door for further optimisations of these
classes to be implemented by using SIMD intrinsics.

This needs to be applied in conjunction with

https://codereview.qt-project.org/#change,33548

Task-number: QTBUG-21035
Task-number: QTBUG-20661
Change-Id: I9321b06040ffb93ae1cbd72fd2013267ac901b2e
Reviewed-by: Lars Knoll <lars.knoll@nokia.com>

1 files changed, 30 insertions, 34 deletions

diff --git a/src/gui/math3d/qvector2d.h b/src/gui/math3d/qvector2d.h
index 882845db1b..34893c2a04 100644
--- a/src/gui/math3d/qvector2d.h
+++ b/src/gui/math3d/qvector2d.h
@@ -60,7 +60,7 @@ class Q_GUI_EXPORT QVector2D
 {
 public:
     QVector2D();
-    QVector2D(qreal xpos, qreal ypos);
+    QVector2D(float xpos, float ypos);
     explicit QVector2D(const QPoint& point);
     explicit QVector2D(const QPointF& point);
 #ifndef QT_NO_VECTOR3D
@@ -72,35 +72,35 @@ public:
 
     bool isNull() const;
 
-    qreal x() const;
-    qreal y() const;
+    float x() const;
+    float y() const;
 
-    void setX(qreal x);
-    void setY(qreal y);
+    void setX(float x);
+    void setY(float y);
 
-    qreal length() const;
-    qreal lengthSquared() const;
+    float length() const;
+    float lengthSquared() const;
 
     QVector2D normalized() const;
     void normalize();
 
     QVector2D &operator+=(const QVector2D &vector);
     QVector2D &operator-=(const QVector2D &vector);
-    QVector2D &operator*=(qreal factor);
+    QVector2D &operator*=(float factor);
     QVector2D &operator*=(const QVector2D &vector);
-    QVector2D &operator/=(qreal divisor);
+    QVector2D &operator/=(float divisor);
 
-    static qreal dotProduct(const QVector2D& v1, const QVector2D& v2);
+    static float dotProduct(const QVector2D& v1, const QVector2D& v2);
 
     friend inline bool operator==(const QVector2D &v1, const QVector2D &v2);
     friend inline bool operator!=(const QVector2D &v1, const QVector2D &v2);
     friend inline const QVector2D operator+(const QVector2D &v1, const QVector2D &v2);
     friend inline const QVector2D operator-(const QVector2D &v1, const QVector2D &v2);
-    friend inline const QVector2D operator*(qreal factor, const QVector2D &vector);
-    friend inline const QVector2D operator*(const QVector2D &vector, qreal factor);
+    friend inline const QVector2D operator*(float factor, const QVector2D &vector);
+    friend inline const QVector2D operator*(const QVector2D &vector, float factor);
     friend inline const QVector2D operator*(const QVector2D &v1, const QVector2D &v2);
     friend inline const QVector2D operator-(const QVector2D &vector);
-    friend inline const QVector2D operator/(const QVector2D &vector, qreal divisor);
+    friend inline const QVector2D operator/(const QVector2D &vector, float divisor);
 
     friend inline bool qFuzzyCompare(const QVector2D& v1, const QVector2D& v2);
 
@@ -119,8 +119,6 @@ public:
 private:
     float xp, yp;
 
-    QVector2D(float xpos, float ypos, int dummy);
-
     friend class QVector3D;
     friend class QVector4D;
 };
@@ -129,9 +127,7 @@ Q_DECLARE_TYPEINFO(QVector2D, Q_MOVABLE_TYPE);
 
 inline QVector2D::QVector2D() : xp(0.0f), yp(0.0f) {}
 
-inline QVector2D::QVector2D(float xpos, float ypos, int) : xp(xpos), yp(ypos) {}
-
-inline QVector2D::QVector2D(qreal xpos, qreal ypos) : xp(xpos), yp(ypos) {}
+inline QVector2D::QVector2D(float xpos, float ypos) : xp(xpos), yp(ypos) {}
 
 inline QVector2D::QVector2D(const QPoint& point) : xp(point.x()), yp(point.y()) {}
 
@@ -142,11 +138,11 @@ inline bool QVector2D::isNull() const
     return qIsNull(xp) && qIsNull(yp);
 }
 
-inline qreal QVector2D::x() const { return qreal(xp); }
-inline qreal QVector2D::y() const { return qreal(yp); }
+inline float QVector2D::x() const { return xp; }
+inline float QVector2D::y() const { return yp; }
 
-inline void QVector2D::setX(qreal aX) { xp = aX; }
-inline void QVector2D::setY(qreal aY) { yp = aY; }
+inline void QVector2D::setX(float aX) { xp = aX; }
+inline void QVector2D::setY(float aY) { yp = aY; }
 
 inline QVector2D &QVector2D::operator+=(const QVector2D &vector)
 {
@@ -162,7 +158,7 @@ inline QVector2D &QVector2D::operator-=(const QVector2D &vector)
     return *this;
 }
 
-inline QVector2D &QVector2D::operator*=(qreal factor)
+inline QVector2D &QVector2D::operator*=(float factor)
 {
     xp *= factor;
     yp *= factor;
@@ -176,7 +172,7 @@ inline QVector2D &QVector2D::operator*=(const QVector2D &vector)
     return *this;
 }
 
-inline QVector2D &QVector2D::operator/=(qreal divisor)
+inline QVector2D &QVector2D::operator/=(float divisor)
 {
     xp /= divisor;
     yp /= divisor;
@@ -195,37 +191,37 @@ inline bool operator!=(const QVector2D &v1, const QVector2D &v2)
 
 inline const QVector2D operator+(const QVector2D &v1, const QVector2D &v2)
 {
-    return QVector2D(v1.xp + v2.xp, v1.yp + v2.yp, 1);
+    return QVector2D(v1.xp + v2.xp, v1.yp + v2.yp);
 }
 
 inline const QVector2D operator-(const QVector2D &v1, const QVector2D &v2)
 {
-    return QVector2D(v1.xp - v2.xp, v1.yp - v2.yp, 1);
+    return QVector2D(v1.xp - v2.xp, v1.yp - v2.yp);
 }
 
-inline const QVector2D operator*(qreal factor, const QVector2D &vector)
+inline const QVector2D operator*(float factor, const QVector2D &vector)
 {
-    return QVector2D(vector.xp * factor, vector.yp * factor, 1);
+    return QVector2D(vector.xp * factor, vector.yp * factor);
 }
 
-inline const QVector2D operator*(const QVector2D &vector, qreal factor)
+inline const QVector2D operator*(const QVector2D &vector, float factor)
 {
-    return QVector2D(vector.xp * factor, vector.yp * factor, 1);
+    return QVector2D(vector.xp * factor, vector.yp * factor);
 }
 
 inline const QVector2D operator*(const QVector2D &v1, const QVector2D &v2)
 {
-    return QVector2D(v1.xp * v2.xp, v1.yp * v2.yp, 1);
+    return QVector2D(v1.xp * v2.xp, v1.yp * v2.yp);
 }
 
 inline const QVector2D operator-(const QVector2D &vector)
 {
-    return QVector2D(-vector.xp, -vector.yp, 1);
+    return QVector2D(-vector.xp, -vector.yp);
 }
 
-inline const QVector2D operator/(const QVector2D &vector, qreal divisor)
+inline const QVector2D operator/(const QVector2D &vector, float divisor)
 {
-    return QVector2D(vector.xp / divisor, vector.yp / divisor, 1);
+    return QVector2D(vector.xp / divisor, vector.yp / divisor);
 }
 
 inline bool qFuzzyCompare(const QVector2D& v1, const QVector2D& v2)