Merge remote-tracking branch 'origin/5.4' into dev

Conflicts:
	.qmake.conf
	src/compositor/compositor_api/qwaylandsurface.cpp

Change-Id: I3ee40153c959dbe31ea685571c5a8bb1ae36606e

src/plugins/platforms/wayland/qwaylanddatadevice.cpp

@@ -126,7 +126,7 @@ void QWaylandDataDevice::data_device_drop()
 
     qDebug() << Q_FUNC_INFO << drag << m_dragOffer.data();
 
-    QMimeData *dragData;
+    QMimeData *dragData = 0;
     Qt::DropActions supportedActions;
     if (drag) {
         dragData = drag->mimeData();

src/plugins/platforms/wayland/qwaylandshmbackingstore.cpp

@@ -46,6 +46,7 @@
 
 #include <QtCore/qdebug.h>
 #include <QtGui/QPainter>
+#include <QMutexLocker>
 
 #include <wayland-client.h>
 #include <unistd.h>
@@ -185,6 +186,7 @@ void QWaylandShmBackingStore::endPaint()
 
 void QWaylandShmBackingStore::hidden()
 {
+    QMutexLocker lock(&mMutex);
     if (mFrameCallback) {
         wl_callback_destroy(mFrameCallback);
         mFrameCallback = Q_NULLPTR;
@@ -347,6 +349,7 @@ void QWaylandShmBackingStore::done(void *data, wl_callback *callback, uint32_t t
             static_cast<QWaylandShmBackingStore *>(data);
     if (callback != self->mFrameCallback) // others, like QWaylandWindow, may trigger callbacks too
         return;
+    QMutexLocker lock(&self->mMutex);
     QWaylandWindow *window = self->waylandWindow();
     wl_callback_destroy(self->mFrameCallback);
     self->mFrameCallback = 0;

src/plugins/platforms/wayland/qwaylandshmbackingstore_p.h

@@ -47,6 +47,7 @@
 #include <qpa/qplatformbackingstore.h>
 #include <QtGui/QImage>
 #include <qpa/qplatformwindow.h>
+#include <QMutex>
 
 QT_BEGIN_NAMESPACE
 
@@ -107,6 +108,7 @@ private:
     QWaylandShmBuffer *mBackBuffer;
     bool mFrontBufferIsDirty;
     bool mPainting;
+    QMutex mMutex;
 
     QSize mRequestedSize;
     Qt::WindowFlags mCurrentWindowFlags;