QColorTransform: make fit for release

- Unexport the value class, export only out-of-line public member functions
  to give us more leeway in changing code later (otherwise, we'd be bound
  by BC with MSVC debug builds, which call even inline methods from the DLL.

- Don't use QSharedPointer as the d_ptr. It's twice the size of a pointer.
  Use a naked pointer-to-const. Derive Private from QSharedData. This
  requires some changes in QColorSpace, and, as usual, an out-of-line copy
  ctor.

- Add member-swap(), Q_DECLARE_SHARED().

- Drop noexcept from the dtor. It implicitly is, adding it explicitly looks
  weird.

- Pass QRgb and QRgba64 by value, not by cref. They're trivially-copyable,
  so passed in registers if passed by value. Passing by cref forces them
  onto the stack.

Change-Id: I669643d219ede6b7d07f15afbf8728e16150b3b2
Reviewed-by: Allan Sandfeld Jensen <allan.jensen@qt.io>

5 files changed, 42 insertions, 31 deletions

diff --git a/src/gui/image/qimage.cpp b/src/gui/image/qimage.cpp
index 61d32b0dec..cd2fe5bc10 100644
--- a/src/gui/image/qimage.cpp
+++ b/src/gui/image/qimage.cpp
@@ -5067,12 +5067,12 @@ void QImage::applyColorTransform(const QColorTransform &transform)
     if (depth() > 32) {
         for (int i = 0; i < height(); ++i) {
             QRgba64 *scanline = reinterpret_cast<QRgba64 *>(scanLine(i));
-            transform.d_func()->apply(scanline, scanline, width(), flags);
+            transform.d->apply(scanline, scanline, width(), flags);
         }
     } else {
         for (int i = 0; i < height(); ++i) {
             QRgb *scanline = reinterpret_cast<QRgb *>(scanLine(i));
-            transform.d_func()->apply(scanline, scanline, width(), flags);
+            transform.d->apply(scanline, scanline, width(), flags);
         }
     }
 
diff --git a/src/gui/painting/qcolorspace.cpp b/src/gui/painting/qcolorspace.cpp
index 8d3bbbe412..72c236bc50 100644
--- a/src/gui/painting/qcolorspace.cpp
+++ b/src/gui/painting/qcolorspace.cpp
@@ -355,10 +355,11 @@ QColorTransform QColorSpacePrivate::transformationToColorSpace(const QColorSpace
 {
     Q_ASSERT(out);
     QColorTransform combined;
-    combined.d_ptr.reset(new QColorTransformPrivate);
-    combined.d_ptr->colorSpaceIn = this;
-    combined.d_ptr->colorSpaceOut = out;
-    combined.d_ptr->colorMatrix = out->toXyz.inverted() * toXyz;
+    auto ptr = new QColorTransformPrivate;
+    combined.d = ptr;
+    ptr->colorSpaceIn = this;
+    ptr->colorSpaceOut = out;
+    ptr->colorMatrix = out->toXyz.inverted() * toXyz;
     return combined;
 }
 
diff --git a/src/gui/painting/qcolortransform.cpp b/src/gui/painting/qcolortransform.cpp
index de08bf4221..53fd1dfbaa 100644
--- a/src/gui/painting/qcolortransform.cpp
+++ b/src/gui/painting/qcolortransform.cpp
@@ -134,8 +134,18 @@ void QColorTransformPrivate::updateLutsOut() const
 */
 
 
-QColorTransform::~QColorTransform() noexcept
+QColorTransform::QColorTransform(const QColorTransform &colorTransform) noexcept
+    : d(colorTransform.d)
 {
+    if (d)
+        d->ref.ref();
+}
+
+
+QColorTransform::~QColorTransform()
+{
+    if (d && !d->ref.deref())
+        delete d;
 }
 
 /*!
@@ -143,11 +153,10 @@ QColorTransform::~QColorTransform() noexcept
 
     The input should be opaque or unpremultiplied.
 */
-QRgb QColorTransform::map(const QRgb &argb) const
+QRgb QColorTransform::map(QRgb argb) const
 {
-    if (!d_ptr)
+    if (!d)
         return argb;
-    Q_D(const QColorTransform);
     constexpr float f = 1.0f / 255.0f;
     QColorVector c = { qRed(argb) * f, qGreen(argb) * f, qBlue(argb) * f };
     c.x = d->colorSpaceIn->trc[0].apply(c.x);
@@ -175,11 +184,10 @@ QRgb QColorTransform::map(const QRgb &argb) const
 
     The input should be opaque or unpremultiplied.
 */
-QRgba64 QColorTransform::map(const QRgba64 &rgba64) const
+QRgba64 QColorTransform::map(QRgba64 rgba64) const
 {
-    if (!d_ptr)
+    if (!d)
         return rgba64;
-    Q_D(const QColorTransform);
     constexpr float f = 1.0f / 65535.0f;
     QColorVector c = { rgba64.red() * f, rgba64.green() * f, rgba64.blue() * f };
     c.x = d->colorSpaceIn->trc[0].apply(c.x);
@@ -208,9 +216,8 @@ QRgba64 QColorTransform::map(const QRgba64 &rgba64) const
 */
 QColor QColorTransform::map(const QColor &color) const
 {
-    if (!d_ptr)
+    if (!d)
         return color;
-    Q_D(const QColorTransform);
     QColor clr = color;
     if (color.spec() != QColor::ExtendedRgb || color.spec() != QColor::Rgb)
         clr = clr.toRgb();
@@ -228,7 +235,7 @@ QColor QColorTransform::map(const QColor &color) const
     c = d->colorMatrix.map(c);
     bool inGamut = c.x >= 0.0f && c.x <= 1.0f && c.y >= 0.0f && c.y <= 1.0f && c.z >= 0.0f && c.z <= 1.0f;
     if (inGamut) {
-        if (d_ptr->colorSpaceOut->lut.generated.loadAcquire()) {
+        if (d->colorSpaceOut->lut.generated.loadAcquire()) {
             c.x = d->colorSpaceOut->lut[0]->fromLinear(c.x);
             c.y = d->colorSpaceOut->lut[1]->fromLinear(c.y);
             c.z = d->colorSpaceOut->lut[2]->fromLinear(c.z);
diff --git a/src/gui/painting/qcolortransform.h b/src/gui/painting/qcolortransform.h
index a83611d666..5fb51739a7 100644
--- a/src/gui/painting/qcolortransform.h
+++ b/src/gui/painting/qcolortransform.h
@@ -51,41 +51,42 @@ class QRgba64;
 class QColorSpacePrivate;
 class QColorTransformPrivate;
 
-class Q_GUI_EXPORT QColorTransform
+class QColorTransform
 {
 public:
-    QColorTransform() noexcept : d_ptr(nullptr) { }
-    ~QColorTransform() noexcept;
-    QColorTransform(const QColorTransform &colorTransform) noexcept
-            : d_ptr(colorTransform.d_ptr)
-    { }
+    QColorTransform() noexcept : d(nullptr) { }
+    Q_GUI_EXPORT ~QColorTransform();
+    Q_GUI_EXPORT QColorTransform(const QColorTransform &colorTransform) noexcept;
     QColorTransform(QColorTransform &&colorTransform) noexcept
-            : d_ptr(std::move(colorTransform.d_ptr))
+            : d{qExchange(colorTransform.d, nullptr)}
     { }
     QColorTransform &operator=(const QColorTransform &other) noexcept
     {
-        d_ptr = other.d_ptr;
+        QColorTransform{other}.swap(*this);
         return *this;
     }
     QColorTransform &operator=(QColorTransform &&other) noexcept
     {
-        d_ptr = std::move(other.d_ptr);
+        QColorTransform{std::move(other)}.swap(*this);
         return *this;
     }
 
-    QRgb map(const QRgb &argb) const;
-    QRgba64 map(const QRgba64 &rgba64) const;
-    QColor map(const QColor &color) const;
+    void swap(QColorTransform &other) noexcept { qSwap(d, other.d); }
+
+    Q_GUI_EXPORT QRgb map(QRgb argb) const;
+    Q_GUI_EXPORT QRgba64 map(QRgba64 rgba64) const;
+    Q_GUI_EXPORT QColor map(const QColor &color) const;
 
 private:
     friend class QColorSpace;
     friend class QColorSpacePrivate;
     friend class QImage;
 
-    Q_DECLARE_PRIVATE(QColorTransform)
-    QSharedPointer<QColorTransformPrivate> d_ptr;
+    const QColorTransformPrivate *d;
 };
 
+Q_DECLARE_SHARED(QColorTransform)
+
 QT_END_NAMESPACE
 
 #endif // QCOLORTRANSFORM_H
diff --git a/src/gui/painting/qcolortransform_p.h b/src/gui/painting/qcolortransform_p.h
index 74a1e7fe0a..5d7116248d 100644
--- a/src/gui/painting/qcolortransform_p.h
+++ b/src/gui/painting/qcolortransform_p.h
@@ -54,9 +54,11 @@
 #include "qcolormatrix_p.h"
 #include "qcolorspace_p.h"
 
+#include <QtCore/qshareddata.h>
+
 QT_BEGIN_NAMESPACE
 
-class QColorTransformPrivate
+class QColorTransformPrivate : public QSharedData
 {
 public:
     QColorMatrix colorMatrix;