source: trunk/src/gui/painting/qpaintengine.cpp@ 938

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#include "qpaintengine.h"
#include "qpaintengine_p.h"
#include "qpainter_p.h"
#include "qpolygon.h"
#include "qbitmap.h"
#include "qapplication.h"
#include <qdebug.h>
#include <qmath.h>
#include <private/qtextengine_p.h>
#include <qvarlengtharray.h>
#include <private/qfontengine_p.h>
#include <private/qpaintengineex_p.h>


QT_BEGIN_NAMESPACE

/*!
    \class QTextItem

    \brief The QTextItem class provides all the information required to draw
    text in a custom paint engine.

    When you reimplement your own paint engine, you must reimplement
    QPaintEngine::drawTextItem(), a function that takes a QTextItem as
    one of its arguments.
*/

/*!
  \enum QTextItem::RenderFlag

  \value  RightToLeft Render the text from right to left.
  \value  Overline    Paint a line above the text.
  \value  Underline   Paint a line under the text.
  \value  StrikeOut   Paint a line through the text.
  \omitvalue Dummy
*/


/*!
    \fn qreal QTextItem::descent() const

    Corresponds to the \l{QFontMetrics::descent()}{descent} of the piece of text that is drawn.
*/
qreal QTextItem::descent() const
{
    const QTextItemInt *ti = static_cast<const QTextItemInt *>(this);
    return ti->descent.toReal();
}

/*!
    \fn qreal QTextItem::ascent() const

    Corresponds to the \l{QFontMetrics::ascent()}{ascent} of the piece of text that is drawn.
*/
qreal QTextItem::ascent() const
{
    const QTextItemInt *ti = static_cast<const QTextItemInt *>(this);
    return ti->ascent.toReal();
}

/*!
    \fn qreal QTextItem::width() const

    Specifies the total width of the text to be drawn.
*/
qreal QTextItem::width() const
{
    const QTextItemInt *ti = static_cast<const QTextItemInt *>(this);
    return ti->width.toReal();
}

/*!
    \fn QTextItem::RenderFlags QTextItem::renderFlags() const

    Returns the render flags used.
*/
QTextItem::RenderFlags QTextItem::renderFlags() const
{
    const QTextItemInt *ti = static_cast<const QTextItemInt *>(this);
    return ti->flags;
}

/*!
    \fn QString QTextItem::text() const

    Returns the text that should be drawn.
*/
QString QTextItem::text() const
{
    const QTextItemInt *ti = static_cast<const QTextItemInt *>(this);
    return QString(ti->chars, ti->num_chars);
}

/*!
    \fn QFont QTextItem::font() const

    Returns the font that should be used to draw the text.
*/
QFont QTextItem::font() const
{
    const QTextItemInt *ti = static_cast<const QTextItemInt *>(this);
    return ti->f ? *ti->f : QApplication::font();
}


/*!
  \class QPaintEngine
  \ingroup painting

  \brief The QPaintEngine class provides an abstract definition of how
  QPainter draws to a given device on a given platform.

  Qt 4.0 provides several premade implementations of QPaintEngine for the
  different painter backends we support. We provide one paint engine for each
  window system and painting framework we support. This includes X11 on
  Unix/Linux and CoreGraphics on Mac OS X. In addition we provide QPaintEngine
  implementations for OpenGL (accessible through QGLWidget) and PostScript
  (accessible through QPSPrinter on X11). Additionally there is a raster-based
  paint engine that is a fallback for when an engine does not support a certain
  capability.

  If one wants to use QPainter to draw to a different backend,
  one must subclass QPaintEngine and reimplement all its virtual
  functions. The QPaintEngine implementation is then made available by
  subclassing QPaintDevice and reimplementing the virtual function
  QPaintDevice::paintEngine().

  QPaintEngine is created and owned by the QPaintDevice that created it.

  The big advantage of the QPaintEngine approach opposed to
  Qt 3's QPainter/QPaintDevice::cmd() approach is that it is now
  possible to adapt to multiple technologies on each platform and take
  advantage of each to the fullest.

  \sa QPainter, QPaintDevice::paintEngine(), {Paint System}
*/

/*!
  \enum QPaintEngine::PaintEngineFeature

  This enum is used to describe the features or capabilities that the
  paint engine has. If a feature is not supported by the engine,
  QPainter will do a best effort to emulate that feature through other
  means and pass on an alpha blended QImage to the engine with the
  emulated results. Some features cannot be emulated: AlphaBlend and PorterDuff.

  \value AlphaBlend         The engine can alpha blend primitives.
  \value Antialiasing       The engine can use antialising to improve the appearance
                            of rendered primitives.
  \value BlendModes         The engine supports blending modes.
  \value BrushStroke        The engine supports drawing strokes that
                            contain brushes as fills, not just solid
                            colors (e.g. a dashed gradient line of
                            width 2).
  \value ConicalGradientFill The engine supports conical gradient fills.
  \value ConstantOpacity    The engine supports the feature provided by
                            QPainter::setOpacity().
  \value LinearGradientFill The engine supports linear gradient fills.
  \value MaskedBrush        The engine is capable of rendering brushes that has a
                            texture with an alpha channel or a mask.
  \value ObjectBoundingModeGradients The engine has native support for gradients
                            with coordinate mode QGradient::ObjectBoundingMode.
                            Otherwise, if QPaintEngine::PatternTransform is
                            supported, object bounding mode gradients are
                            converted to gradients with coordinate mode
                            QGradient::LogicalMode and a brush transform for
                            the coordinate mapping.
  \value PainterPaths       The engine has path support.
  \value PaintOutsidePaintEvent The engine is capable of painting outside of
                                paint events.
  \value PatternBrush       The engine is capable of rendering brushes with
                            the brush patterns specified in Qt::BrushStyle.
  \value PatternTransform   The engine has support for transforming brush
                            patterns.
  \value PerspectiveTransform The engine has support for performing perspective
                            transformations on primitives.
  \value PixmapTransform    The engine can transform pixmaps, including
                            rotation and shearing.
  \value PorterDuff         The engine supports Porter-Duff operations
  \value PrimitiveTransform The engine has support for transforming
                            drawing primitives.
  \value RadialGradientFill The engine supports radial gradient fills.
  \value RasterOpModes      The engine supports bitwise raster operations.
  \value AllFeatures        All of the above features. This enum value is usually
                            used as a bit mask.
*/

/*!
    \enum QPaintEngine::PolygonDrawMode

    \value OddEvenMode The polygon should be drawn using OddEven fill
    rule.

    \value WindingMode The polygon should be drawn using Winding fill rule.

    \value ConvexMode The polygon is a convex polygon and can be drawn
    using specialized algorithms where available.

    \value PolylineMode Only the outline of the polygon should be
    drawn.

*/

/*!
    \enum QPaintEngine::DirtyFlag

    \value DirtyPen The pen is dirty and needs to be updated.

    \value DirtyBrush The brush is dirty and needs to be updated.

    \value DirtyBrushOrigin The brush origin is dirty and needs to
    updated.

    \value DirtyFont The font is dirty and needs to be updated.

    \value DirtyBackground The background is dirty and needs to be
    updated.

    \value DirtyBackgroundMode The background mode is dirty and needs
    to be updated.

    \value DirtyTransform The transform is dirty and needs to be
    updated.

    \value DirtyClipRegion The clip region is dirty and needs to be
    updated.

    \value DirtyClipPath The clip path is dirty and needs to be
    updated.

    \value DirtyHints The render hints is dirty and needs to be
    updated.

    \value DirtyCompositionMode The composition mode is dirty and
    needs to be updated.

    \value DirtyClipEnabled Whether clipping is enabled or not is
    dirty and needs to be updated.

    \value DirtyOpacity The constant opacity has changed and needs to
                        be updated as part of the state change in
                        QPaintEngine::updateState().

    \value AllDirty Convenience enum used internally.

    These types are used by QPainter to trigger lazy updates of the
    various states in the QPaintEngine using
    QPaintEngine::updateState().

    A paint engine must update every dirty state.
*/

/*!
    \fn void QPaintEngine::syncState()

    \internal

    Updates all dirty states in this engine. This function should ONLY
    be used when drawing with native handles directly and immediate sync
    from QPainters state to the native state is required.
*/
void QPaintEngine::syncState()
{
    Q_ASSERT(state);
    updateState(*state);

    if (isExtended())
        static_cast<QPaintEngineEx *>(this)->sync();
}

static QPaintEngine *qt_polygon_recursion = 0;
struct QT_Point {
    int x;
    int y;
};

/*!
    \fn void QPaintEngine::drawPolygon(const QPointF *points, int pointCount,
    PolygonDrawMode mode)

    Reimplement this virtual function to draw the polygon defined
    by the \a pointCount first points in \a points, using mode \a
    mode.

    \note At least one of the drawPolygon() functions must be reimplemented.
*/
void QPaintEngine::drawPolygon(const QPointF *points, int pointCount, PolygonDrawMode mode)
{
    Q_ASSERT_X(qt_polygon_recursion != this, "QPaintEngine::drawPolygon",
               "At least one drawPolygon function must be implemented");
    qt_polygon_recursion = this;
    Q_ASSERT(sizeof(QT_Point) == sizeof(QPoint));
    QVarLengthArray<QT_Point> p(pointCount);
    for (int i = 0; i < pointCount; ++i) {
        p[i].x = qRound(points[i].x());
        p[i].y = qRound(points[i].y());
    }
    drawPolygon((QPoint *)p.data(), pointCount, mode);
    qt_polygon_recursion = 0;
}

struct QT_PointF {
    qreal x;
    qreal y;
};
/*!
    \overload

    Reimplement this virtual function to draw the polygon defined by the
    \a pointCount first points in \a points, using mode \a mode.

    \note At least one of the drawPolygon() functions must be reimplemented.
*/
void QPaintEngine::drawPolygon(const QPoint *points, int pointCount, PolygonDrawMode mode)
{
    Q_ASSERT_X(qt_polygon_recursion != this, "QPaintEngine::drawPolygon",
               "At least one drawPolygon function must be implemented");
    qt_polygon_recursion = this;
    Q_ASSERT(sizeof(QT_PointF) == sizeof(QPointF));
    QVarLengthArray<QT_PointF> p(pointCount);
    for (int i=0; i<pointCount; ++i) {
        p[i].x = points[i].x();
        p[i].y = points[i].y();
    }
    drawPolygon((QPointF *)p.data(), pointCount, mode);
    qt_polygon_recursion = 0;
}

/*!
    \enum QPaintEngine::Type

    \value X11
    \value Windows
    \value MacPrinter
    \value CoreGraphics Mac OS X's Quartz2D (CoreGraphics)
    \value QuickDraw Mac OS X's QuickDraw
    \value QWindowSystem Qt for Embedded Linux