Add devicePixelRatio support to the Windows QPA plugin.

This adds support for the environment variable
QT_DEVICE_PIXEL_RATIO for the Windows platform plugin.

Task-number: QTBUG-38993
Task-number: QTBUG-38858
Change-Id: I6831eb6d3a09a80be7bbef46395e91531b61cc50
Reviewed-by: Alessandro Portale <alessandro.portale@digia.com>
Reviewed-by: Paul Olav Tvete <paul.tvete@digia.com>

1 files changed, 114 insertions, 0 deletions

diff --git a/src/plugins/platforms/windows/qwindowsscaling.h b/src/plugins/platforms/windows/qwindowsscaling.h
new file mode 100644
index 0000000000..99fec7c810
--- /dev/null
+++ b/src/plugins/platforms/windows/qwindowsscaling.h
@@ -0,0 +1,114 @@
+/****************************************************************************
+**
+** Copyright (C) 2014 Digia Plc and/or its subsidiary(-ies).
+** Contact: http://www.qt-project.org/legal
+**
+** This file is part of the plugins 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.
+**
+**
+** $QT_END_LICENSE$
+**
+****************************************************************************/
+
+#ifndef QWINDOWSSCALING_H
+#define QWINDOWSSCALING_H
+
+#include <QtGui/QRegion>
+#include <QtCore/QVector>
+#include <QtCore/QRect>
+
+QT_BEGIN_NAMESPACE
+
+enum
+#if defined(Q_COMPILER_CLASS_ENUM) || defined(Q_CC_MSVC)
+     : int
+#endif
+{ QWINDOWSIZE_MAX = 16777215 };
+
+class QWindowsScaling {
+public:
+    static bool isActive() { return m_factor > 1; }
+    static int factor()  { return m_factor; }
+    static void setFactor(int factor) { m_factor = factor; }
+    static int determineUiScaleFactor();
+
+    // Scaling helpers for size constraints.
+    static int mapToNativeConstrained(int qt)
+        { return m_factor != 1 && qt > 0 && qt < QWINDOWSIZE_MAX ? qt * m_factor : qt; }
+
+    static int mapFromNativeConstrained(int dp)
+        { return m_factor != 1 && dp > 0 && dp < QWINDOWSIZE_MAX ? dp / m_factor : dp; }
+
+    static QSize mapToNativeConstrained(const QSize &qt)
+        { return QSize(mapToNativeConstrained(qt.width()), mapToNativeConstrained(qt.height())); }
+
+    static QRect mapToNative(const QRect &qRect)
+    {
+        return QRect(qRect.x() * m_factor, qRect.y() * m_factor, qRect.width() * m_factor, qRect.height() * m_factor);
+    }
+
+    static QRect mapFromNative(const QRect &dp)
+    {
+        return isActive() ?
+            QRect(dp.x() / m_factor, dp.y() / m_factor, (dp.width() + 1) / m_factor, (dp.height() + 1) / m_factor) :
+            dp;
+    }
+
+    static QRegion mapToNative(const QRegion &regionQt)
+    {
+        if (!QWindowsScaling::isActive() || regionQt.isEmpty())
+            return regionQt;
+
+        QRegion result;
+        foreach (const QRect &rectQt, regionQt.rects())
+            result += QWindowsScaling::mapToNative(rectQt);
+        return result;
+    }
+
+    static QRegion mapFromNative(const QRegion &regionDp)
+    {
+        if (!QWindowsScaling::isActive() || regionDp.isEmpty())
+            return regionDp;
+
+        QRegion result;
+        foreach (const QRect &rectDp, regionDp.rects())
+            result += QWindowsScaling::mapFromNative(rectDp);
+        return result;
+    }
+
+private:
+    static int m_factor;
+};
+
+QT_END_NAMESPACE
+
+#endif // QWINDOWSSCALING_H