Implement high-dpi "@2x" image handling.

Make QQuickBaseImage::load() load "@2x" image files
on high-dpi displays. Reload images on screen change
in order to load the correct version depending on
screen dpi. Modify QQuickImageBase::updatePaintNode()
to work with @2x images.

QQuickBaseImage::load() now looks at the target
window's devicePixelRatio and checks for the presence
of a "@2x" file on disk. If found the @2x version
will be used.

Unlike QPixmap, QQuickPixmap has no special knowledge
of "@2x" files. They pixmap system will be asked to
load "@2x" files and will cache them and report the
(device) pixel size, like any other pixmap.

Add auto-test and manual test.

Task-number: QTBUG-32862, QTBUG-33069
Change-Id: I1f57a10075e499f6eee61df5421e1986521c6ab0
Reviewed-by: Andy Nichols <andy.nichols@digia.com>

1 files changed, 64 insertions, 0 deletions

diff --git a/tests/manual/highdpi/image2.qml b/tests/manual/highdpi/image2.qml
new file mode 100644
index 0000000000..b83c8006d8
--- /dev/null
+++ b/tests/manual/highdpi/image2.qml
@@ -0,0 +1,64 @@
+/****************************************************************************
+**
+** Copyright (C) 2014 Digia Plc and/or its subsidiary(-ies).
+** Contact: http://www.qt-project.org/legal
+**
+** This file is part of the QtQml module 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 2.0
+
+Rectangle {
+    width: 400
+    height: 400
+
+    // These images should all have the same visual size:
+    Row {
+        anchors.centerIn: parent
+        // 1X only
+        Image {
+            source : "heart-lowdpi.png"
+        }
+        // 1X and 2x, switches on screen change.
+        Image {
+            source : "heart.png"
+        }
+        // 2x only
+        Image {
+            source : "heart-highdpi@2x.png"
+        }
+    }
+}