QtGui: replace some copies with swaps

This provides move speed even for non-C++11 compilers and avoids
having to call the copy assignment operator from within copy ctors.
(which will result in infinite recursion when using the copy-swap idiom).

Change-Id: I379bc8bf2c72d9f986c0f17f9eef56cd592e7a06
Reviewed-by: Thiago Macieira <thiago.macieira@intel.com>
Reviewed-by: Gunnar Sletta <gunnar.sletta@nokia.com>
Reviewed-by: Girish Ramakrishnan <girish.1.ramakrishnan@nokia.com>

3 files changed, 4 insertions, 5 deletions

diff --git a/src/gui/image/qbitmap.cpp b/src/gui/image/qbitmap.cpp
index 59756d8693..f7ab853905 100644
--- a/src/gui/image/qbitmap.cpp
+++ b/src/gui/image/qbitmap.cpp
@@ -187,8 +187,7 @@ QBitmap::QBitmap(const QString& fileName, const char *format)
 QBitmap &QBitmap::operator=(const QPixmap &pixmap)
 {
     if (pixmap.isNull()) {                        // a null pixmap
-        QBitmap bm(0, 0);
-        QBitmap::operator=(bm);
+        QBitmap(0, 0).swap(*this);
     } else if (pixmap.depth() == 1) {                // 1-bit pixmap
         QPixmap::operator=(pixmap);                // shallow assignment
     } else {                                        // n-bit depth pixmap
diff --git a/src/gui/image/qimage.cpp b/src/gui/image/qimage.cpp
index b16ae2ffce..71ec636839 100644
--- a/src/gui/image/qimage.cpp
+++ b/src/gui/image/qimage.cpp
@@ -983,7 +983,7 @@ QImage::QImage(const QImage &image)
 {
     if (image.paintingActive() || isLocked(image.d)) {
         d = 0;
-        operator=(image.copy());
+        image.copy().swap(*this);
     } else {
         d = image.d;
         if (d)
diff --git a/src/gui/image/qpixmap.cpp b/src/gui/image/qpixmap.cpp
index 183c13698a..c1a63f5101 100644
--- a/src/gui/image/qpixmap.cpp
+++ b/src/gui/image/qpixmap.cpp
@@ -226,7 +226,7 @@ QPixmap::QPixmap(const QPixmap &pixmap)
         return;
     }
     if (pixmap.paintingActive()) {                // make a deep copy
-        operator=(pixmap.copy());
+        pixmap.copy().swap(*this);
     } else {
         data = pixmap.data;
     }
@@ -384,7 +384,7 @@ QPixmap &QPixmap::operator=(const QPixmap &pixmap)
         return *this;
     }
     if (pixmap.paintingActive()) {                // make a deep copy
-        *this = pixmap.copy();
+        pixmap.copy().swap(*this);
     } else {
         data = pixmap.data;
     }