QFixed{,Size}: reformulate some functions in a constexpr-friendly way

The main change is the addition of a new constructor
that passes its argument into 'val' verbatim. In order
to disambiguate it from the existing QFixed(int)
constructor, it takes a second 'int' argument. This
is too ugly for public API, so it's private, and only
used by static QFixed fromFixed(int), which is the
existing named constructor with the same semantics.

The rest of the changes simply reformulate their
operations in terms of fromFixed().

This makes them ready to be constexpr'ed.

Change-Id: I2a3813d62bd4124064755de6b00526a60fc82c1d
Reviewed-by: Olivier Goffart <ogoffart@woboq.com>

1 files changed, 24 insertions, 23 deletions

diff --git a/src/gui/painting/qfixed_p.h b/src/gui/painting/qfixed_p.h
index d30328b0fa..95fb6893b3 100644
--- a/src/gui/painting/qfixed_p.h
+++ b/src/gui/painting/qfixed_p.h
@@ -60,6 +60,8 @@
 QT_BEGIN_NAMESPACE
 
 struct QFixed {
+private:
+    QFixed(int val, int) : val(val) {} // 2nd int is just a dummy for disambiguation
 public:
     QFixed() : val(0) {}
     QFixed(int i) : val(i<<6) {}
@@ -67,8 +69,8 @@ public:
     QFixed &operator=(int i) { val = (i<<6); return *this; }
     QFixed &operator=(long i) { val = (i<<6); return *this; }
 
-    static QFixed fromReal(qreal r) { QFixed f; f.val = (int)(r*qreal(64)); return f; }
-    static QFixed fromFixed(int fixed) { QFixed f; f.val = fixed; return f; }
+    static QFixed fromReal(qreal r) { return fromFixed((int)(r*qreal(64))); }
+    static QFixed fromFixed(int fixed) { return QFixed(fixed,0); } // uses private ctor
 
     inline int value() const { return val; }
     inline void setValue(int value) { val = value; }
@@ -77,23 +79,23 @@ public:
     inline qreal toReal() const { return ((qreal)val)/(qreal)64; }
 
     inline int truncate() const { return val>>6; }
-    inline QFixed round() const { QFixed f; f.val = ((val)+32) & -64; return f; }
-    inline QFixed floor() const { QFixed f; f.val = (val) & -64; return f; }
-    inline QFixed ceil() const { QFixed f; f.val = (val+63) & -64; return f; }
+    inline QFixed round() const { return fromFixed(((val)+32) & -64); }
+    inline QFixed floor() const { return fromFixed((val) & -64); }
+    inline QFixed ceil() const { return fromFixed((val+63) & -64); }
 
-    inline QFixed operator+(int i) const { QFixed f; f.val = (val + (i<<6)); return f; }
-    inline QFixed operator+(uint i) const { QFixed f; f.val = (val + (i<<6)); return f; }
-    inline QFixed operator+(const QFixed &other) const { QFixed f; f.val = (val + other.val); return f; }
+    inline QFixed operator+(int i) const { return fromFixed((val + (i<<6))); }
+    inline QFixed operator+(uint i) const { return fromFixed((val + (i<<6))); }
+    inline QFixed operator+(const QFixed &other) const { return fromFixed((val + other.val)); }
     inline QFixed &operator+=(int i) { val += (i<<6); return *this; }
     inline QFixed &operator+=(uint i) { val += (i<<6); return *this; }
     inline QFixed &operator+=(const QFixed &other) { val += other.val; return *this; }
-    inline QFixed operator-(int i) const { QFixed f; f.val = (val - (i<<6)); return f; }
-    inline QFixed operator-(uint i) const { QFixed f; f.val = (val - (i<<6)); return f; }
-    inline QFixed operator-(const QFixed &other) const { QFixed f; f.val = (val - other.val); return f; }
+    inline QFixed operator-(int i) const { return fromFixed((val - (i<<6))); }
+    inline QFixed operator-(uint i) const { return fromFixed((val - (i<<6))); }
+    inline QFixed operator-(const QFixed &other) const { return fromFixed((val - other.val)); }
     inline QFixed &operator-=(int i) { val -= (i<<6); return *this; }
     inline QFixed &operator-=(uint i) { val -= (i<<6); return *this; }
     inline QFixed &operator-=(const QFixed &other) { val -= other.val; return *this; }
-    inline QFixed operator-() const { QFixed f; f.val = -val; return f; }
+    inline QFixed operator-() const { return fromFixed(-val); }
 
     inline bool operator==(const QFixed &other) const { return val == other.val; }
     inline bool operator!=(const QFixed &other) const { return val != other.val; }
@@ -120,7 +122,7 @@ public:
         }
         return *this;
     }
-    inline QFixed operator/(int d) const { QFixed f; f.val = val/d; return f; }
+    inline QFixed operator/(int d) const { return fromFixed(val/d); }
     inline QFixed operator/(QFixed b) const { QFixed f = *this; return (f /= b); }
     inline QFixed operator>>(int d) const { QFixed f = *this; f.val >>= d; return f; }
     inline QFixed &operator*=(int i) { val *= i; return *this; }
@@ -136,21 +138,21 @@ public:
         val = neg ? -res : res;
         return *this;
     }
-    inline QFixed operator*(int i) const { QFixed f = *this; return (f *= i); }
-    inline QFixed operator*(uint i) const { QFixed f = *this; return (f *= i); }
+    inline QFixed operator*(int i) const { return fromFixed(val * i); }
+    inline QFixed operator*(uint i) const { return fromFixed(val * i); }
     inline QFixed operator*(const QFixed &o) const { QFixed f = *this; return (f *= o); }
 
 private:
     QFixed(qreal i) : val((int)(i*qreal(64))) {}
     QFixed &operator=(qreal i) { val = (int)(i*qreal(64)); return *this; }
-    inline QFixed operator+(qreal i) const { QFixed f; f.val = (val + (int)(i*qreal(64))); return f; }
+    inline QFixed operator+(qreal i) const { return fromFixed((val + (int)(i*qreal(64)))); }
     inline QFixed &operator+=(qreal i) { val += (int)(i*64); return *this; }
-    inline QFixed operator-(qreal i) const { QFixed f; f.val = (val - (int)(i*qreal(64))); return f; }
+    inline QFixed operator-(qreal i) const { return fromFixed((val - (int)(i*qreal(64)))); }
     inline QFixed &operator-=(qreal i) { val -= (int)(i*64); return *this; }
     inline QFixed &operator/=(qreal r) { val = (int)(val/r); return *this; }
-    inline QFixed operator/(qreal d) const { QFixed f; f.val = (int)(val/d); return f; }
+    inline QFixed operator/(qreal d) const { return fromFixed((int)(val/d)); }
     inline QFixed &operator*=(qreal d) { val = (int) (val*d); return *this; }
-    inline QFixed operator*(qreal d) const { QFixed f = *this; return (f *= d); }
+    inline QFixed operator*(qreal d) const { return fromFixed((int) (val*d)); }
     int val;
 };
 Q_DECLARE_TYPEINFO(QFixed, Q_PRIMITIVE_TYPE);
@@ -206,12 +208,11 @@ inline QFixedPoint operator+(const QFixedPoint &p1, const QFixedPoint &p2)
 struct QFixedSize {
     QFixed width;
     QFixed height;
+    QFixedSize() {}
+    QFixedSize(QFixed _width, QFixed _height) : width(_width), height(_height) {}
     QSizeF toSizeF() const { return QSizeF(width.toReal(), height.toReal()); }
     static QFixedSize fromSizeF(const QSizeF &s) {
-        QFixedSize size;
-        size.width = QFixed::fromReal(s.width());
-        size.height = QFixed::fromReal(s.height());
-        return size;
+        return QFixedSize(QFixed::fromReal(s.width()), QFixed::fromReal(s.height()));
     }
 };
 Q_DECLARE_TYPEINFO(QFixedSize, Q_PRIMITIVE_TYPE);