qpainter.cpp

奇趣公司比较新的qt/emd版本

    bool conicalGradient = false;
    bool patternBrush = false;
    bool xform = false;
    bool complexXform = false;

    bool skip = true;

    // Pen and brush properties (we have to check both if one changes because the
    // one that's unchanged can still be in a state which requires emulation)
    if (s->state() & QPaintEngine::DirtyPen ||
        s->state() & QPaintEngine::DirtyBrush) {
        // Check Brush stroke emulation
        if (!s->pen.isSolid() && !engine->hasFeature(QPaintEngine::BrushStroke))
            s->emulationSpecifier |= QPaintEngine::BrushStroke;
        else
            s->emulationSpecifier &= ~QPaintEngine::BrushStroke;

        skip = false;

        QBrush penBrush = s->pen.brush();
        Qt::BrushStyle brushStyle = s->brush.style();
        Qt::BrushStyle penBrushStyle = penBrush.style();
        alpha = (penBrushStyle != Qt::NoBrush
                 && (penBrushStyle < Qt::LinearGradientPattern && penBrush.color().alpha() != 255)
                 && !penBrush.isOpaque())
                || (brushStyle != Qt::NoBrush
                    && (brushStyle < Qt::LinearGradientPattern && s->brush.color().alpha() != 255)
                    && !s->brush.isOpaque());
        linearGradient = ((penBrushStyle == Qt::LinearGradientPattern) ||
                           (brushStyle == Qt::LinearGradientPattern));
        radialGradient = ((penBrushStyle == Qt::RadialGradientPattern) ||
                           (brushStyle == Qt::RadialGradientPattern));
        conicalGradient = ((penBrushStyle == Qt::ConicalGradientPattern) ||
                            (brushStyle == Qt::ConicalGradientPattern));
        patternBrush = (((penBrushStyle > Qt::SolidPattern
                           && penBrushStyle < Qt::LinearGradientPattern)
                          || penBrushStyle == Qt::TexturePattern) ||
                         ((brushStyle > Qt::SolidPattern
                           && brushStyle < Qt::LinearGradientPattern)
                          || brushStyle == Qt::TexturePattern));

        if (((penBrush.style() == Qt::TexturePattern && penBrush.texture().hasAlpha())
             || (s->brush.style() == Qt::TexturePattern && s->brush.texture().hasAlpha()))
            && !engine->hasFeature(QPaintEngine::MaskedBrush))
            s->emulationSpecifier |= QPaintEngine::MaskedBrush;
        else
            s->emulationSpecifier &= ~QPaintEngine::MaskedBrush;
    }

    if (s->state() & (QPaintEngine::DirtyHints
                      | QPaintEngine::DirtyOpacity
                      | QPaintEngine::DirtyBackgroundMode)) {
        skip = false;
    }

    if (skip)
        return;

#if 0
    qDebug("QPainterPrivate::updateEmulationSpecifier, state=%p\n"
           " - alpha: %d\n"
           " - linearGradient: %d\n"
           " - radialGradient: %d\n"
           " - conicalGradient: %d\n"
           " - patternBrush: %d\n"
           " - hints: %x\n"
           " - xform: %d\n",
           s,
           alpha,
           linearGradient,
           radialGradient,
           conicalGradient,
           patternBrush,
           uint(s->renderHints),
           xform);
#endif

    // XForm properties
    if (s->state() & QPaintEngine::DirtyTransform) {
        xform = !s->matrix.isIdentity();
        complexXform = !s->matrix.isAffine();
    } else if (s->txop >= QTransform::TxTranslate) {
        xform = true;
        complexXform = !s->matrix.isAffine();
    }

    const bool brushXform = (!s->brush.transform().type() == QTransform::TxNone);
    const bool penXform = (!s->pen.brush().transform().type() == QTransform::TxNone);

    const bool patternXform = patternBrush && (xform || brushXform || penXform);

    // Check alphablending
    if (alpha && !engine->hasFeature(QPaintEngine::AlphaBlend))
        s->emulationSpecifier |= QPaintEngine::AlphaBlend;
    else
        s->emulationSpecifier &= ~QPaintEngine::AlphaBlend;

    // Linear gradient emulation
    if (linearGradient && !engine->hasFeature(QPaintEngine::LinearGradientFill))
        s->emulationSpecifier |= QPaintEngine::LinearGradientFill;
    else
        s->emulationSpecifier &= ~QPaintEngine::LinearGradientFill;

    // Radial gradient emulation
    if (radialGradient && !engine->hasFeature(QPaintEngine::RadialGradientFill))
        s->emulationSpecifier |= QPaintEngine::RadialGradientFill;
    else
        s->emulationSpecifier &= ~QPaintEngine::RadialGradientFill;

    // Conical gradient emulation
    if (conicalGradient && !engine->hasFeature(QPaintEngine::ConicalGradientFill))
        s->emulationSpecifier |= QPaintEngine::ConicalGradientFill;
    else
        s->emulationSpecifier &= ~QPaintEngine::ConicalGradientFill;

    // Pattern brushes
    if (patternBrush && !engine->hasFeature(QPaintEngine::PatternBrush))
        s->emulationSpecifier |= QPaintEngine::PatternBrush;
    else
        s->emulationSpecifier &= ~QPaintEngine::PatternBrush;

    // Pattern XForms
    if (patternXform && !engine->hasFeature(QPaintEngine::PatternTransform))
        s->emulationSpecifier |= QPaintEngine::PatternTransform;
    else
        s->emulationSpecifier &= ~QPaintEngine::PatternTransform;

    // Primitive XForms
    if (xform && !engine->hasFeature(QPaintEngine::PrimitiveTransform))
        s->emulationSpecifier |= QPaintEngine::PrimitiveTransform;
    else
        s->emulationSpecifier &= ~QPaintEngine::PrimitiveTransform;

    // Perspective XForms
    if (complexXform && !engine->hasFeature(QPaintEngine::PerspectiveTransform))
        s->emulationSpecifier |= QPaintEngine::PerspectiveTransform;
    else
        s->emulationSpecifier &= ~QPaintEngine::PerspectiveTransform;

    // Constant opacity
    if (state->opacity != 1 && !engine->hasFeature(QPaintEngine::ConstantOpacity))
        s->emulationSpecifier |= QPaintEngine::ConstantOpacity;
    else
        s->emulationSpecifier &= ~QPaintEngine::ConstantOpacity;

    bool gradientStretch = false;
    if (linearGradient || conicalGradient || radialGradient) {
        gradientStretch |= check_gradient(s->brush);
        gradientStretch |= check_gradient(s->pen.brush());
    }
    if (gradientStretch)
        s->emulationSpecifier |= QGradient_StretchToDevice;
    else
        s->emulationSpecifier &= ~QGradient_StretchToDevice;

    // Opaque backgrounds...
    if (s->bgMode == Qt::OpaqueMode &&
        (is_pen_transparent(s->pen) || is_brush_transparent(s->brush)))
        s->emulationSpecifier |= QPaintEngine_OpaqueBackground;
    else
        s->emulationSpecifier &= ~QPaintEngine_OpaqueBackground;

#if 0
    //won't be correct either way because the device can already have
    // something rendered to it in which case subsequent emulation
    // on a fully transparent qimage and then blitting the results
    // won't produce correct results
    // Blend modes
    if (state->composition_mode > QPainter::CompositionMode_Xor &&
        !engine->hasFeature(QPaintEngine::BlendModes))
        s->emulationSpecifier |= QPaintEngine::BlendModes;
    else
        s->emulationSpecifier &= ~QPaintEngine::BlendModes;
#endif
}



void QPainterPrivate::updateState(QPainterState *newState)
{

    if (!newState) {
        engine->state = newState;

    } else if (newState->state() || engine->state!=newState) {

        // ### we might have to call QPainter::begin() here...
        if (!engine->state) {
            engine->state = newState;
            engine->setDirty(QPaintEngine::AllDirty);
        }

        if (engine->state->painter() != newState->painter)
            // ### this could break with clip regions vs paths.
            engine->setDirty(QPaintEngine::AllDirty);

        // Upon restore, revert all changes since last save
        else if (engine->state != newState)
            newState->dirtyFlags |= QPaintEngine::DirtyFlags(static_cast<QPainterState *>(engine->state)->changeFlags);

        // We need to store all changes made so that restore can deal with them
        else
            newState->changeFlags |= newState->dirtyFlags;

        updateEmulationSpecifier(newState);

        // Unset potential dirty background mode
        newState->dirtyFlags &= ~(QPaintEngine::DirtyBackgroundMode
                                  | QPaintEngine::DirtyBackground);

        engine->state = newState;
        engine->updateState(*newState);
        engine->clearDirty(QPaintEngine::AllDirty);
    }
}


/*!
    \class QPainter
    \brief The QPainter class performs low-level painting on widgets and
    other paint devices.

    \ingroup multimedia
    \mainclass

    QPainter provides highly optimized functions to do most of the
    drawing GUI programs require. It can draw everything from simple
    lines to complex shapes like pies and chords. It can also draw
    aligned text and pixmaps. Normally, it draws in a "natural"
    coordinate system, but it can also do view and world
    transformation. QPainter can operate on any object that inherits
    the QPaintDevice class.

    The common use of QPainter is inside a widget's paint event:
    Construct and customize (e.g. set the pen or the brush) the
    painter. Then draw. Remember to destroy the QPainter object after
    drawing. For example:

    \code
    void SimpleExampleWidget::paintEvent(QPaintEvent *)
    {
        QPainter painter(this);
        painter.setPen(Qt::blue);
        painter.setFont(QFont("Arial", 30));
        painter.drawText(rect(), Qt::AlignCenter, "Qt");
    }
    \endcode

    The core functionality of QPainter is drawing, but the class also
    provide several functions that allows you to customize QPainter's
    settings and its rendering quality, and others that enable
    clipping. In addition you can control how different shapes are
    merged together by specifying the painter's composition mode.

    The isActive() function indicates whether the painter is active. A
    painter is activated by the begin() function and the constructor
    that takes a QPaintDevice argument. The end() function, and the
    destructor, deactivates it.

    Together with the QPaintDevice and QPaintEngine classes, QPainter
    form the basis for Qt's paint system. QPainter is the class used
    to perform drawing operations. QPaintDevice represents a device
    that can be painted on using a QPainter. QPaintEngine provides the
    interface that the painter uses to draw onto different types of
    devices. If the painter is active, device() returns the paint
    device on which the painter paints, and paintEngine() returns the
    paint engine that the painter is currently operating on. For more
    information, see \l {The Paint System} documentation.

    Sometimes it is desirable to make someone else paint on an unusual
    QPaintDevice. QPainter supports a static function to do this,
    setRedirected().

    \warning When the paintdevice is a widget, QPainter can only be
    used inside a paintEvent() function or in a function called by
    paintEvent(); that is unless the Qt::WA_PaintOutsidePaintEvent
    widget attribute is set. On Mac OS X and Windows, you can only
    paint in a paintEvent() function regardless of this attribute's
    setting.

    \tableofcontents

    \section1 Settings

    There are several settings that you can customize to make QPainter
    draw according to your preferences:

    \list

    \o font() is the font used for drawing text. If the painter
        isActive(), you can retrieve information about the currently set
        font, and its metrics, using the fontInfo() and fontMetrics()
        functions respectively.

    \o brush() defines the color or pattern that is used for filling
       shapes.

    \o pen() defines the color or stipple that is used for drawing
       lines or boundaries.

    \o backgroundMode() defines whether there is a background() or
       not, i.e it is either Qt::OpaqueMode or Qt::TransparentMode.

    \o background() only applies when backgroundMode() is \l
       Qt::OpaqueMode and pen() is a stipple. In that case, it
       describes the color of the background pixels in the stipple.

    \o brushOrigin() defines the origin of the tiled brushes, normally
       the origin of widget's background.

    \o viewport(), window(), worldMatrix() make up the painter's coordinate
        transformation system. For more information, see the \l
        {Coordinate Transformations} section and the \l {The Coordinate
        System} documentation.

    \o hasClipping() tells whether the painter clips at all. (The paint
       device clips, too.) If the painter clips, it clips to clipRegion().

    \o layoutDirection() defines the layout direction used by the
       painter when drawing text.

    \o matrixEnabled() tells whether world transformation is enabled.

    \o viewTransformEnabled() tells whether view transformation is
        enabled.

    \endlist

    Note that some of these settings mirror settings in some paint
    devices, e.g.  QWidget::font(). The QPainter::begin() function (or
    equivalently the QPainter constructor) copies these attributes
    from the paint device.

    You can at any time save the QPainter's state by calling the
    save() function which saves all the available settings on an
    internal stack. The restore() function pops them back.

    \section1 Drawing

    QPainter provides functions to draw most primitives: drawPoint(),
    drawPoints(), drawLine(), drawRect(), drawRoundRect(),
    drawEllipse(), drawArc(), drawPie(), drawChord(), drawPolyline(),
    drawPolygon(), drawConvexPolygon() and drawCubicBezier().  The two
    convenience functions, drawRects() and drawLines(), draw the given
    number of rectangles or lines in the given array of \l
    {QRect}{QRects} or \l {QLine}{QLines} using the current pen and
    brush.

    The QPainter class also provides the fillRect() function which
    fills the given QRect, with the given QBrush, and the eraseRect()
    function that erases the area inside the given rectangle.

    All of these functions have both integer and floating point
    versions.

    \table 100%
    \row
    \o \inlineimage qpainter-basicdrawing.png
    \o
    \bold {Basic Drawing Example}

    The \l {painting/basicdrawing}{Basic Drawing} example shows how to
    display basic graphics primitives in a variety of styles using the
    QPainter class.

    \endtable

    If you need to draw a complex shape, especially if you need to do
    so repeatedly, consider creating a QPainterPath and drawing it
    using drawPath().

    \table 100%
    \row
    \o
    \bold {Painter Paths example}

    The QPainterPath class provides a container for painting
    operations, enabling graphical shapes to be constructed and
    reused.

    The \l {painting/painterpaths}{Painter Paths} example shows how
    painter paths can be used to build complex shapes for rendering.

    \o \inlineimage qpainter-painterpaths.png
    \endtable

    QPainter also provides the fillPath() function which fills the
    given QPainterPath with the given QBrush, and the strokePath()