Merge "Merge remote-tracking branch 'origin/5.12' into 5.13" into refs/staging/5.13

2 files changed, 13 insertions, 4 deletions

diff --git a/src/gui/painting/qbrush.cpp b/src/gui/painting/qbrush.cpp
index abfa8d41bb..ed575abf54 100644
--- a/src/gui/painting/qbrush.cpp
+++ b/src/gui/painting/qbrush.cpp
@@ -545,9 +545,11 @@ QBrush::QBrush(const QBrush &other)
 */
 QBrush::QBrush(const QGradient &gradient)
 {
-    Q_ASSERT_X(gradient.type() != QGradient::NoGradient, "QBrush::QBrush",
-               "QGradient should not be used directly, use the linear, radial\n"
-               "or conical gradients instead");
+    if (Q_UNLIKELY(gradient.type() == QGradient::NoGradient)) {
+        d.reset(nullBrushInstance());
+        d->ref.ref();
+        return;
+    }
 
     const Qt::BrushStyle enum_table[] = {
         Qt::LinearGradientPattern,
@@ -1376,8 +1378,10 @@ QGradient::QGradient(Preset preset)
         }();
 
         const QJsonValue presetData = jsonPresets[preset - 1];
-        if (!presetData.isObject())
+        if (!presetData.isObject()) {
+            qWarning("QGradient: Undefined preset %i", preset);
             return;
+        }
 
         m_type = LinearGradient;
         setCoordinateMode(ObjectMode);
diff --git a/src/gui/painting/qplatformbackingstore.cpp b/src/gui/painting/qplatformbackingstore.cpp
index afb4613ba5..c71d82546a 100644
--- a/src/gui/painting/qplatformbackingstore.cpp
+++ b/src/gui/painting/qplatformbackingstore.cpp
@@ -446,6 +446,11 @@ void QPlatformBackingStore::composeAndFlush(QWindow *window, const QRegion &regi
             d_ptr->blitter->setRedBlueSwizzle(false);
     }
 
+    // There is no way to tell if the OpenGL-rendered content is premultiplied or not.
+    // For compatibility, assume that it is not, and use normal alpha blend always.
+    if (d_ptr->premultiplied)
+        funcs->glBlendFuncSeparate(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA, GL_ONE, GL_ONE);
+
     // Textures for renderToTexture widgets that have WA_AlwaysStackOnTop set.
     for (int i = 0; i < textures->count(); ++i) {
         if (textures->flags(i).testFlag(QPlatformTextureList::StacksOnTop))