Introduce QFontEngineDirectWrite

Make a font engine for subpixel positioned text on Windows Vista
(with platform update) and Windows 7. If selected during
configuration, the engine will be selected only when the hinting
preference of a font is set to None or Vertical hinting. The font
database uses most of the same logic but creates a direct write
font based on the LOGFONT rather than a GDI handle.

The engine is currently regarded as experimental, meaning that code
using it should do substantial testing to make sure it covers their
use cases.

Task-number: QTBUG-12678
Reviewed-by: Jiang Jiang

1 files changed, 133 insertions, 0 deletions

diff --git a/src/gui/text/qfontenginedirectwrite_p.h b/src/gui/text/qfontenginedirectwrite_p.h
new file mode 100644
index 0000000..80f90b8
--- /dev/null
+++ b/src/gui/text/qfontenginedirectwrite_p.h
@@ -0,0 +1,133 @@
+/****************************************************************************
+**
+** Copyright (C) 2011 Nokia Corporation and/or its subsidiary(-ies).
+** All rights reserved.
+** Contact: Nokia Corporation (qt-info@nokia.com)
+**
+** This file is part of the QtGui module of the Qt Toolkit.
+**
+** $QT_BEGIN_LICENSE:LGPL$
+** No Commercial Usage
+** This file contains pre-release code and may not be distributed.
+** You may use this file in accordance with the terms and conditions
+** contained in the Technology Preview License Agreement accompanying
+** this package.
+**
+** 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, 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.
+**
+** If you have questions regarding the use of this file, please contact
+** Nokia at qt-info@nokia.com.
+**
+**
+**
+**
+**
+**
+**
+**
+** $QT_END_LICENSE$
+**
+****************************************************************************/
+
+#ifndef QFONTENGINEDIRECTWRITE_H
+#define QFONTENGINEDIRECTWRITE_H
+
+#ifndef QT_NO_DIRECTWRITE
+
+//
+//  W A R N I N G
+//  -------------
+//
+// This file is not part of the Qt API.  It exists purely as an
+// implementation detail.  This header file may change from version to
+// version without notice, or even be removed.
+//
+// We mean it.
+//
+
+#include "private/qfontengine_p.h"
+
+struct IDWriteFont ;
+struct IDWriteFontFace ;
+struct IDWriteFactory ;
+struct IDWriteBitmapRenderTarget ;
+struct IDWriteGdiInterop ;
+
+QT_BEGIN_NAMESPACE
+
+class QFontEngineDirectWrite : public QFontEngine
+{
+    Q_OBJECT
+public:
+    explicit QFontEngineDirectWrite(const QString &name,
+                                    IDWriteFactory *directWriteFactory,
+                                    IDWriteGdiInterop *directWriteGdiInterop,
+                                    IDWriteFont *directWriteFont,
+                                    qreal pixelSize);
+    ~QFontEngineDirectWrite();
+
+    QFixed lineThickness() const;
+    bool getSfntTableData(uint tag, uchar *buffer, uint *length) const;
+    QFixed emSquareSize() const;
+
+    bool stringToCMap(const QChar *str, int len, QGlyphLayout *glyphs, int *nglyphs, QTextEngine::ShaperFlags flags) const;
+    void recalcAdvances(QGlyphLayout *glyphs, QTextEngine::ShaperFlags) const;
+
+    void addGlyphsToPath(glyph_t *glyphs, QFixedPoint *positions, int nglyphs,
+                         QPainterPath *path, QTextItem::RenderFlags flags);
+
+    glyph_metrics_t boundingBox(const QGlyphLayout &glyphs);
+    glyph_metrics_t boundingBox(glyph_t g);
+
+    QFixed ascent() const;
+    QFixed descent() const;
+    QFixed leading() const;
+    QFixed xHeight() const;
+    qreal maxCharWidth() const;
+
+    const char *name() const;
+
+    bool supportsSubPixelPositions() const;
+
+    QImage alphaMapForGlyph(glyph_t glyph, QFixed subPixelPosition);
+    QImage alphaRGBMapForGlyph(glyph_t t, QFixed subPixelPosition, int margin,
+                               const QTransform &xform);
+
+    bool canRender(const QChar *string, int len);
+    Type type() const;
+
+private:
+    QImage imageForGlyph(glyph_t t, QFixed subPixelPosition, int margin, const QTransform &xform);
+    void collectMetrics();
+
+    QString m_name;
+    IDWriteFont *m_directWriteFont;
+    IDWriteFontFace *m_directWriteFontFace;
+    IDWriteFactory *m_directWriteFactory;
+    IDWriteBitmapRenderTarget *m_directWriteBitmapRenderTarget;
+    IDWriteGdiInterop *m_directWriteGdiInterop;
+
+    QFixed m_lineThickness;
+    int m_unitsPerEm;
+    QFixed m_ascent;
+    QFixed m_descent;
+    QFixed m_xHeight;
+    QFixed m_lineGap;
+    FaceId m_faceId;
+};
+
+QT_END_NAMESPACE
+
+#endif // QT_NO_DIRECTWRITE
+
+#endif // QFONTENGINEDIRECTWRITE_H