Fix stacking order bug in the renderer

Since we are sorting batches based on the zorder of the first element
it is crucial that we don't continue adding to batches once an overlap
with a compatible element is found.

Task-number: QTBUG-34864
Change-Id: Ic2194c5c17bba0bc9874a14e8a69c81bff75bd1c
Reviewed-by: Sean Harmer <sean.harmer@kdab.com>

diff --git a/src/quick/scenegraph/coreapi/qsgbatchrenderer.cpp b/src/quick/scenegraph/coreapi/qsgbatchrenderer.cpp
index 49c2cc8..79b5de7 100644 (file)
--- a/src/quick/scenegraph/coreapi/qsgbatchrenderer.cpp
+++ b/src/quick/scenegraph/coreapi/qsgbatchrenderer.cpp
@@ -1572,6 +1572,13 @@ void Renderer::prepareAlphaBatches()
                     ej->batch = batch;
                     next->nextInBatch = ej;
                     next = ej;
+                } else {
+                    /* When we come across a compatible element which hits an overlap, we
+                     * need to stop the batch right away. We cannot add more elements
+                     * to the current batch as they will be rendered before the batch that the
+                     * current 'ej' will be added to.
+                     */
+                    break;
                 }
             } else {
                 overlapBounds |= ej->bounds;

diff --git a/tests/auto/quick/scenegraph/data/render_StackingOrder.qml b/tests/auto/quick/scenegraph/data/render_StackingOrder.qml
new file mode 100644 (file)
index 0000000..ab33500
--- /dev/null
+++ b/tests/auto/quick/scenegraph/data/render_StackingOrder.qml
@@ -0,0 +1,65 @@
+/****************************************************************************
+**
+** Copyright (C) 2013 Digia Plc and/or its subsidiary(-ies).
+** Contact: http://www.qt-project.org/legal
+**
+** This file is part of the test suite of the Qt Toolkit.
+**
+** $QT_BEGIN_LICENSE:LGPL$
+** Commercial License Usage
+** Licensees holding valid commercial Qt licenses may use this file in
+** accordance with the commercial license agreement provided with the
+** Software or, alternatively, in accordance with the terms contained in
+** a written agreement between you and Digia.  For licensing terms and
+** conditions see http://qt.digia.com/licensing.  For further information
+** use the contact form at http://qt.digia.com/contact-us.
+**
+** GNU Lesser General Public License Usage
+** Alternatively, this file may be used under the terms of the GNU Lesser
+** General Public License version 2.1 as published by the Free Software
+** Foundation and appearing in the file LICENSE.LGPL included in the
+** packaging of this file.  Please review the following information to
+** ensure the GNU Lesser General Public License version 2.1 requirements
+** will be met: http://www.gnu.org/licenses/old-licenses/lgpl-2.1.html.
+**
+** In addition, as a special exception, Digia gives you certain additional
+** rights.  These rights are described in the Digia Qt LGPL Exception
+** version 1.1, included in the file LGPL_EXCEPTION.txt in this package.
+**
+** GNU General Public License Usage
+** Alternatively, this file may be used under the terms of the GNU
+** General Public License version 3.0 as published by the Free Software
+** Foundation and appearing in the file LICENSE.GPL included in the
+** packaging of this file.  Please review the following information to
+** ensure the GNU General Public License version 3.0 requirements will be
+** met: http://www.gnu.org/copyleft/gpl.html.
+**
+**
+** $QT_END_LICENSE$
+**
+****************************************************************************/
+
+import QtQuick 2.2
+
+/*
+    This test verifies that items that go from being batched because
+    of no overlap will be split into multiple batches because of an
+    overlap and that no rendering errors occur as a result of this.
+
+    #samples: 3
+                 PixelPos     R    G    B    Error-tolerance
+    #final:       10  10     1.0  0.0  0.0       0.05
+    #final:       10 110     0.0  1.0  0.0       0.05
+    #final:       10 120     0.0  0.0  1.0       0.05
+*/
+
+RenderTestBase {
+    Item {
+        opacity: 0.99; // Just to trigger alpha batches
+        Rectangle { color: "#ff0000";  x: 10;  y: 10;  width: 20;  height: 20; }
+        Image { source: "logo-small.jpg";  x: 10;  y: 50;   width: 50; height: 51; }
+        Rectangle { color: "#00ff00"; x: 10;  y: 100; width: 50; height: 50; }
+        Rectangle { color: "#0000ff"; x: 10;  y: 120; width: 10; height: 10; }
+    }
+    onEnterFinalStage: finalStageComplete = true;
+}

diff --git a/tests/auto/quick/scenegraph/tst_scenegraph.cpp b/tests/auto/quick/scenegraph/tst_scenegraph.cpp
index 755cec4..3b79f01 100644 (file)
--- a/tests/auto/quick/scenegraph/tst_scenegraph.cpp
+++ b/tests/auto/quick/scenegraph/tst_scenegraph.cpp
@@ -323,6 +323,7 @@ void tst_SceneGraph::render_data()
           << "data/render_MovingOverlap.qml"
           << "data/render_BreakOpacityBatch.qml"
           << "data/render_OutOfFloatRange.qml"
+          << "data/render_StackingOrder.qml"
         ;
 
     QRegExp sampleCount("#samples: *(\\d+)");