Merge remote-tracking branch 'origin/5.6' into 5.7

Conflicts:
	configure
	src/plugins/platforms/winrt/qwinrtclipboard.cpp

Change-Id: Ic6d58be3d1ed2bb507f2ba06c82361afd9f9ddb9

4 files changed, 9 insertions, 8 deletions

diff --git a/src/gui/kernel/qoffscreensurface.cpp b/src/gui/kernel/qoffscreensurface.cpp
index 41f7251277..a9535a6ad7 100644
--- a/src/gui/kernel/qoffscreensurface.cpp
+++ b/src/gui/kernel/qoffscreensurface.cpp
@@ -183,7 +183,7 @@ void QOffscreenSurface::create()
             if (QThread::currentThread() != qGuiApp->thread())
                 qWarning("Attempting to create QWindow-based QOffscreenSurface outside the gui thread. Expect failures.");
             d->offscreenWindow = new QWindow(d->screen);
-            d->offscreenWindow->setObjectName("QOffscreenSurface");
+            d->offscreenWindow->setObjectName(QLatin1String("QOffscreenSurface"));
             // Remove this window from the global list since we do not want it to be destroyed when closing the app.
             // The QOffscreenSurface has to be usable even after exiting the event loop.
             QGuiApplicationPrivate::window_list.removeOne(d->offscreenWindow);
diff --git a/src/gui/painting/qdrawhelper.cpp b/src/gui/painting/qdrawhelper.cpp
index 8729640a80..30d3dee473 100644
--- a/src/gui/painting/qdrawhelper.cpp
+++ b/src/gui/painting/qdrawhelper.cpp
@@ -5753,9 +5753,9 @@ static inline void rgbBlendPixel(quint32 *dst, int coverage, int sr, int sg, int
     dg = gamma[dg];
     db = gamma[db];
 
-    int nr = qt_div_255((sr - dr) * mr) + dr;
-    int ng = qt_div_255((sg - dg) * mg) + dg;
-    int nb = qt_div_255((sb - db) * mb) + db;
+    int nr = qt_div_255(sr * mr + dr * (255 - mr));
+    int ng = qt_div_255(sg * mg + dg * (255 - mg));
+    int nb = qt_div_255(sb * mb + db * (255 - mb));
 
     nr = invgamma[nr];
     ng = invgamma[ng];
@@ -5780,9 +5780,9 @@ static inline void grayBlendPixel(quint32 *dst, int coverage, int sr, int sg, in
 
     int alpha = coverage;
     int ialpha = 255 - alpha;
-    int nr = (sr * alpha + ialpha * dr) / 255;
-    int ng = (sg * alpha + ialpha * dg) / 255;
-    int nb = (sb * alpha + ialpha * db) / 255;
+    int nr = qt_div_255(sr * alpha + dr * ialpha);
+    int ng = qt_div_255(sg * alpha + dg * ialpha);
+    int nb = qt_div_255(sb * alpha + db * ialpha);
 
     nr = invgamma[nr];
     ng = invgamma[ng];
diff --git a/src/gui/painting/qdrawhelper_p.h b/src/gui/painting/qdrawhelper_p.h
index 21af6039f8..fa3e6396ec 100644
--- a/src/gui/painting/qdrawhelper_p.h
+++ b/src/gui/painting/qdrawhelper_p.h
@@ -760,6 +760,7 @@ static Q_ALWAYS_INLINE uint BYTE_MUL_RGB16_32(uint x, uint a) {
     return t;
 }
 
+// qt_div_255 is a fast rounded division by 255 using an approximation that is accurate for all positive 16-bit integers
 static Q_DECL_CONSTEXPR Q_ALWAYS_INLINE int qt_div_255(int x) { return (x + (x>>8) + 0x80) >> 8; }
 static Q_DECL_CONSTEXPR Q_ALWAYS_INLINE uint qt_div_65535(uint x) { return (x + (x>>16) + 0x8000U) >> 16; }
 
diff --git a/src/gui/text/qtextdocument.cpp b/src/gui/text/qtextdocument.cpp
index 723918ae69..bb44c19557 100644
--- a/src/gui/text/qtextdocument.cpp
+++ b/src/gui/text/qtextdocument.cpp
@@ -1315,7 +1315,7 @@ QTextCursor QTextDocument::find(const QString &subString, int from, FindFlags op
     //do not include the character given in the position.
     if (options & FindBackward) {
         --pos ;
-        if (pos < subString.size())
+        if (pos < 0)
             return QTextCursor();
     }