From 2f319f3be999eb2462515cfcf2dff505592e73f5 Mon Sep 17 00:00:00 2001
From: Volker Hilsheimer <volker.hilsheimer@qt.io>
Date: Fri, 11 Sep 2020 13:37:49 +0200
Subject: [PATCH] Give QPixmap a move constructor

It already has a move-assignment operator, and implements swapping.

This requires a specialization of the QExplicitlySharedDataPointer
destructor to be forward declared, and an implementation that is
identical to the default version. Otherwise we would need
QPlatformPixmap to be fully defined in the public QPixmap header.

Change-Id: I2651bbc29a7083a93e3b3ad671d3aeea659b7d5a
Reviewed-by: Allan Sandfeld Jensen <allan.jensen@qt.io>
---
 src/gui/image/qpixmap.cpp                    |  9 +++++++++
 src/gui/image/qpixmap.h                      |  2 ++
 tests/auto/gui/image/qpixmap/tst_qpixmap.cpp | 15 +++++++++++++++
 3 files changed, 26 insertions(+)

diff --git a/src/gui/image/qpixmap.cpp b/src/gui/image/qpixmap.cpp
index 3847366b4d..c3ae853795 100644
--- a/src/gui/image/qpixmap.cpp
+++ b/src/gui/image/qpixmap.cpp
@@ -224,6 +224,15 @@ QPixmap::QPixmap(const QPixmap &pixmap)
     }
 }
 
+/*! \fn QPixmap::QPixmap(QPixmap &&other)
+    Move-constructs a QPixmap instance from \a other.
+
+    \sa swap() operator=(QPixmap&&)
+*/
+template<>
+QExplicitlySharedDataPointer<QPlatformPixmap>::~QExplicitlySharedDataPointer()
+{ if (d && !d->ref.deref()) delete d; }
+
 /*!
     Constructs a pixmap from the given \a xpm data, which must be a
     valid XPM image.
diff --git a/src/gui/image/qpixmap.h b/src/gui/image/qpixmap.h
index 19881bda2c..b30bef0f6b 100644
--- a/src/gui/image/qpixmap.h
+++ b/src/gui/image/qpixmap.h
@@ -57,6 +57,7 @@ class QImageReader;
 class QColor;
 class QVariant;
 class QPlatformPixmap;
+template<> Q_GUI_EXPORT QExplicitlySharedDataPointer<QPlatformPixmap>::~QExplicitlySharedDataPointer();
 
 class Q_GUI_EXPORT QPixmap : public QPaintDevice
 {
@@ -70,6 +71,7 @@ public:
     explicit QPixmap(const char * const xpm[]);
 #endif
     QPixmap(const QPixmap &);
+    QPixmap(QPixmap &&other) noexcept : QPaintDevice(), data(std::move(other.data)) {}
     ~QPixmap();
 
     QPixmap &operator=(const QPixmap &);
diff --git a/tests/auto/gui/image/qpixmap/tst_qpixmap.cpp b/tests/auto/gui/image/qpixmap/tst_qpixmap.cpp
index 33e8671671..39d58effd3 100644
--- a/tests/auto/gui/image/qpixmap/tst_qpixmap.cpp
+++ b/tests/auto/gui/image/qpixmap/tst_qpixmap.cpp
@@ -118,6 +118,7 @@ private slots:
     void refUnref();
 
     void copy();
+    void move();
     void deepCopyPreservesDpr();
     void dprPassthrough();
     void depthOfNullObjects();
@@ -1142,6 +1143,20 @@ void tst_QPixmap::copy()
     QCOMPARE(trans, transCopy);
 }
 
+void tst_QPixmap::move()
+{
+    QPixmap moveFrom(32, 32);
+
+    QPixmap moveAssigned;
+    moveAssigned = std::move(moveFrom);
+    QVERIFY(!moveAssigned.isNull());
+    QVERIFY(moveFrom.isNull());
+
+    QPixmap moveConstructed(std::move(moveAssigned));
+    QVERIFY(moveAssigned.isNull());
+    QVERIFY(!moveConstructed.isNull());
+}
+
 // QTBUG-58653: Force a deep copy of a pixmap by
 // having a QPainter and check whether DevicePixelRatio is preserved
 void tst_QPixmap::deepCopyPreservesDpr()