Introduce FontSmoothingGamma as a platform style hint.

- Allocate gamma tables on the heap in a thread-safe way, use
  font smoothing returned by the style hints of the platform to
  calculate them.
- Improve font rendering on Windows.

Change-Id: I8cd39b51cf03cbd642474c02b9076814baecd597
Reviewed-by: Samuel Rødal <samuel.rodal@nokia.com>

1 files changed, 66 insertions, 0 deletions

diff --git a/src/gui/painting/qgammatables.cpp b/src/gui/painting/qgammatables.cpp
new file mode 100644
index 0000000000..06dc95a103
--- /dev/null
+++ b/src/gui/painting/qgammatables.cpp
@@ -0,0 +1,66 @@
+/****************************************************************************
+**
+** Copyright (C) 2012 Nokia Corporation and/or its subsidiary(-ies).
+** Contact: http://www.qt-project.org/
+**
+** This file is part of the QtGui module of the Qt Toolkit.
+**
+** $QT_BEGIN_LICENSE:LGPL$
+** GNU Lesser General Public License Usage
+** 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, Nokia gives you certain additional
+** rights. These rights are described in the Nokia 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.
+**
+** Other Usage
+** Alternatively, this file may be used in accordance with the terms and
+** conditions contained in a signed written agreement between you and Nokia.
+**
+**
+**
+**
+**
+**
+** $QT_END_LICENSE$
+**
+****************************************************************************/
+
+#include <private/qdrawhelper_p.h>
+
+QT_BEGIN_NAMESPACE
+
+
+QDrawHelperGammaTables::QDrawHelperGammaTables(qreal smoothing)
+{
+    const qreal gray_gamma = 2.31;
+    for (int i=0; i<256; ++i)
+        qt_pow_gamma[i] = uint(qRound(qPow(i / qreal(255.), gray_gamma) * 2047));
+    for (int i=0; i<2048; ++i)
+        qt_pow_invgamma[i] = uchar(qRound(qPow(i / qreal(2047.0), 1 / gray_gamma) * 255));
+
+    refresh(smoothing);
+}
+
+void QDrawHelperGammaTables::refresh(qreal smoothing)
+{
+    for (int i=0; i<256; ++i) {
+        qt_pow_rgb_gamma[i] = uchar(qRound(qPow(i / qreal(255.0), smoothing) * 255));
+        qt_pow_rgb_invgamma[i] = uchar(qRound(qPow(i / qreal(255.), 1 / smoothing) * 255));
+    }
+}
+
+QT_END_NAMESPACE