QOpenGLBuffer: add move-SMFs and swap()s

- add move special member functions (docs copied from QHostInfo)

- add member swap

- use move-and-swap, not pure-swap, because these objects hold
  resources (handles) other than just memory

- Q_DECLARE_SHARED (it's not implicitly shared, but explicitly)
  - adds ADL swap and Q_DECLARE_TYPEINFO

[ChangeLog][QtOpenGL][QOpenGLBuffer] Added member-swap(), move
constructor, move assignment operator.

Change-Id: I22dc92108bdd393fff4361db23e94eaf3d7ea9cc
Reviewed-by: Fabian Kosmale <fabian.kosmale@qt.io>

1 files changed, 32 insertions, 2 deletions

diff --git a/src/opengl/qopenglbuffer.cpp b/src/opengl/qopenglbuffer.cpp
index 62d2d5edd2..64e7975043 100644
--- a/src/opengl/qopenglbuffer.cpp
+++ b/src/opengl/qopenglbuffer.cpp
@@ -166,7 +166,7 @@ QOpenGLBuffer::QOpenGLBuffer(const QOpenGLBuffer &other)
 */
 QOpenGLBuffer::~QOpenGLBuffer()
 {
-    if (!d_ptr->ref.deref()) {
+    if (d_ptr && !d_ptr->ref.deref()) {
         destroy();
         delete d_ptr;
     }
@@ -182,7 +182,7 @@ QOpenGLBuffer &QOpenGLBuffer::operator=(const QOpenGLBuffer &other)
 {
     if (d_ptr != other.d_ptr) {
         other.d_ptr->ref.ref();
-        if (!d_ptr->ref.deref()) {
+        if (d_ptr && !d_ptr->ref.deref()) {
             destroy();
             delete d_ptr;
         }
@@ -192,6 +192,36 @@ QOpenGLBuffer &QOpenGLBuffer::operator=(const QOpenGLBuffer &other)
 }
 
 /*!
+    \fn QOpenGLBuffer::QOpenGLBuffer(QOpenGLBuffer &&other)
+    \since 6.5
+
+    Move-constructs a new QOpenGLBuffer from \a other.
+
+    \note The moved-from object \a other is placed in a partially-formed state,
+    in which the only valid operations are destruction and assignment of a new
+    value.
+*/
+
+/*!
+    \fn QOpenGLBuffer &QOpenGLBuffer::operator=(QOpenGLBuffer &&other)
+    \since 6.5
+
+    Move-assigns \a other to this QOpenGLBuffer instance.
+
+    \note The moved-from object \a other is placed in a partially-formed state,
+    in which the only valid operations are destruction and assignment of a new
+    value.
+*/
+
+/*!
+    \fn QOpenGLBuffer::swap(QOpenGLBuffer &other)
+    \since 6.5
+
+    Swaps buffer \a other with this buffer. This operation is very fast and
+    never fails.
+*/
+
+/*!
     Returns the type of buffer represented by this object.
 */
 QOpenGLBuffer::Type QOpenGLBuffer::type() const