qpainter.cpp

奇趣公司比较新的qt/emd版本

    Note that while the brushOrigin() was necessary to adopt the
    parent's background for a widget in Qt 3, this is no longer the
    case since the Qt 4 painter doesn't paint the background unless
    you explicitly tell it to do so by setting the widget's \l
    {QWidget::autoFillBackground}{autoFillBackground} property to
    true.

    \sa brushOrigin(), {QPainter#Settings}{Settings}
*/

void QPainter::setBrushOrigin(const QPointF &p)
{
    Q_D(QPainter);
#ifdef QT_DEBUG_DRAW
    if (qt_show_painter_debug_output)
        printf("QPainter::setBrushOrigin(), (%.2f,%.2f)\n", p.x(), p.y());
#endif
    d->state->bgOrigin = p;
    d->state->dirtyFlags |= QPaintEngine::DirtyBrushOrigin;
}

/*!
    \fn void QPainter::setBrushOrigin(const QPoint &position)
    \overload

    Sets the brush's origin to the given \a position.
*/

/*!
    \fn void QPainter::setBrushOrigin(int x, int y)

    \overload

    Sets the brush's origin to point (\a x, \a y).
*/

/*!
    \enum QPainter::CompositionMode

    Defines the Porter-Duff rules for digital image
    compositing. Composition modes are used to specify how the pixels
    in one image, the source, are merged with the pixel in another
    image, the destination.

     \image qpainter-compositionmode1.png
     \image qpainter-compositionmode2.png

    The most common type is SourceOver (often referred to as just
    alpha blending) where the source pixel is blended on top of the
    destination pixel in such a way that the alpha component of the
    source defines the translucency of the pixel.

    When the paint device is a QImage, the image format must be set to
    \l {QImage::Format}{Format_ARGB32Premultiplied} or
    \l {QImage::Format}{Format_ARGB32} for the composition modes to have
    any effect. For performance the premultiplied version is the preferred
    format.

    When a composition mode is set it applies to all painting
    operator, pens, brushes, gradients and pixmap/image drawing.

    \value CompositionMode_SourceOver This is the default mode. The
    alpha of the source is used to blend the pixel on top of the
    destination.

    \value CompositionMode_DestinationOver The alpha of the
    destination is used to blend it on top of the source pixels. This
    mode is the inverse of CompositionMode_SourceOver.

    \value CompositionMode_Clear The pixels in the destination are
    cleared (set to fully transparent) independent of the source.

    \value CompositionMode_Source The output is the source
    pixel. (This means a basic copy operation and is identical to
    SourceOver when the source pixel is opaque).

    \value CompositionMode_Destination The output is the destination
    pixel. This means that the blending has no effect. This mode is
    the inverse of CompositionMode_Source.

    \value CompositionMode_SourceIn The output is the source, where
    the alpha is reduced by that of the destination.

    \value CompositionMode_DestinationIn The output is the
    destination, where the alpha is reduced by that of the
    source. This mode is the inverse of CompositionMode_SourceIn.

    \value CompositionMode_SourceOut The output is the source, where
    the alpha is reduced by the inverse of destination.

    \value CompositionMode_DestinationOut The output is the
    destination, where the alpha is reduced by the inverse of the
    source. This mode is the inverse of CompositionMode_SourceOut.

    \value CompositionMode_SourceAtop The source pixel is blended on
    top of the destination, with the alpha of the source pixel reduced
    by the alpha of the destination pixel.

    \value CompositionMode_DestinationAtop The destination pixel is
    blended on top of the source, with the alpha of the destination
    pixel is reduced by the alpha of the destination pixel. This mode
    is the inverse of CompositionMode_SourceAtop.

    \value CompositionMode_Xor The source, whose alpha is reduced with
    the inverse of the destination alpha, is merged with the
    destination, whose alpha is reduced by the inverse of the source
    alpha. CompositionMode_Xor is not the same as the bitwise Xor.

    \value CompositionMode_Plus Both the alpha and color of the source
    and destination pixels are added together.

    \value CompositionMode_Multiply The output is the source color
    multiplied by the destination. Multiplying a color with white
    leaves the color unchanged, while multiplying a color
    with black produces black.

    \value CompositionMode_Screen The source and destination colors
    are inverted and then multiplied. Screening a color with white
    produces white, whereas screening a color with black leaves the
    color unchanged.

    \value CompositionMode_Overlay Multiplies or screens the colors
    depending on the destination color. The destination color is mixed
    with the source color to reflect the lightness or darkness of the
    destination.

    \value CompositionMode_Darken The darker of the source and destination
    colors is selected.

    \value CompositionMode_Lighten The lighter of the source and destination
    colors is selected.

    \value CompositionMode_ColorDodge The destination color is brightened
    to reflect the source color. A black source color leaves the destination
    color unchanged.

    \value CompositionMode_ColorBurn The destination color is darkened to
    reflect the source color. A white source color leaves the destination color
    unchanged.

    \value CompositionMode_HardLight Multiplies or screens the colors depending
    on the source color. A light source color will lighten the destination color,
    whereas a dark source color will darken the destination color.

    \value CompositionMode_SoftLight Darkens or lightens the colors depending on the
    source color. Similar to CompositionMode_HardLight.

    \value CompositionMode_Difference Subtracts the darker of the colors from the lighter.
    Painting with white inverts the destination color, whereas painting with black leaves the
    destination color unchanged.

    \value CompositionMode_Exclusion Similar to CompositionMode_Difference,
    but with a lower contrast. Painting with white inverts the destination color, whereas painting
    with black leaves the destination color unchanged.

    \sa compositionMode(), setCompositionMode(), {QPainter#Composition
    Modes}{Composition Modes}, {Image Composition Example}
*/

/*!
    Sets the composition mode to the given \a mode.

    \warning You can only set the composition mode for QPainter
    objects that operates on a QImage.

    \sa compositionMode()
*/
void QPainter::setCompositionMode(CompositionMode mode)
{
    Q_D(QPainter);
    if (!isActive()) {
        qWarning("QPainter::setCompositionMode: Painter not active");
        return;
    } else if (!d->engine->hasFeature(QPaintEngine::PorterDuff)) {
        qWarning("QPainter::setCompositionMode: PorterDuff modes not supported on device");
        return;
    }

    if (mode > QPainter::CompositionMode_Xor &&
        !d->engine->hasFeature(QPaintEngine::BlendModes)) {
        qWarning("QPainter::setCompositionMode: Blend modes not supported on device");
        return;
    }

    d->state->composition_mode = mode;
    d->state->dirtyFlags |= QPaintEngine::DirtyCompositionMode;
}

/*!
  Returns the current composition mode.

  \sa CompositionMode, setCompositionMode()
*/
QPainter::CompositionMode QPainter::compositionMode() const
{
    Q_D(const QPainter);
    return d->state->composition_mode;
}

/*!
    Returns the current background brush.

    \sa setBackground(), {QPainter#Settings}{Settings}
*/

const QBrush &QPainter::background() const
{
    Q_D(const QPainter);
    return d->state->bgBrush;
}


/*!
    Returns true if clipping has been set; otherwise returns false.

    \sa setClipping(), {QPainter#Clipping}{Clipping}
*/

bool QPainter::hasClipping() const
{
    Q_D(const QPainter);
    return d->state->clipEnabled && d->state->clipOperation != Qt::NoClip;
}


/*!
    Enables clipping if  \a enable is true, or disables clipping if  \a
    enable is false.

    \sa hasClipping(), {QPainter#Clipping}{Clipping}
*/

void QPainter::setClipping(bool enable)
{
    Q_D(QPainter);
#ifdef QT_DEBUG_DRAW
    if (qt_show_painter_debug_output)
        printf("QPainter::setClipping(), enable=%s, was=%s\n",
               enable ? "on" : "off",
               hasClipping() ? "on" : "off");
#endif
    if (!isActive()) {
        qWarning("QPainter::setClipping: Painter not active, state will be reset by begin");
        return;
    }

    if (hasClipping() == enable)
        return;

    // we can't enable clipping if we don't have a clip
    if (enable
        && (d->state->clipInfo.isEmpty() || d->state->clipInfo.last().operation == Qt::NoClip))
        return;

    if (enable)
        d->state->clipEnabled = true;
    else
        d->state->clipEnabled = false;

    d->state->dirtyFlags |= QPaintEngine::DirtyClipEnabled;
    d->updateState(d->state);
}


/*!
    Returns the currently set clip region. Note that the clip region
    is given in logical coordinates.

    \sa setClipRegion(), clipPath(), setClipping()
*/

QRegion QPainter::clipRegion() const
{
    if (!isActive()) {
        qWarning("QPainter::clipRegion: Painter not active");
        return QRegion();
    }

    Q_D(const QPainter);
    QRegion region;
    bool lastWasNothing = true;

    if (!d->txinv)
        const_cast<QPainter *>(this)->d_ptr->updateInvMatrix();

    for (int i=0; i<d->state->clipInfo.size(); ++i) {
        const QPainterClipInfo &info = d->state->clipInfo.at(i);
        QRegion other;
        switch (info.clipType) {

        case QPainterClipInfo::RegionClip: {
            QTransform matrix = (info.matrix * d->invMatrix);
            if (lastWasNothing) {
                region = info.region * matrix;
                lastWasNothing = false;
                continue;
            }
            if (info.operation == Qt::IntersectClip)
                region &= info.region * matrix;
            else if (info.operation == Qt::UniteClip)
                region |= info.region * matrix;
            else if (info.operation == Qt::NoClip) {
                lastWasNothing = true;
                region = QRegion();
            } else
                region = info.region * matrix;
            break;
        }

        case QPainterClipInfo::PathClip: {
            QTransform matrix = (info.matrix * d->invMatrix);
            if (lastWasNothing) {
                region = QRegion((info.path * matrix).toFillPolygon().toPolygon(),
                                 info.path.fillRule());
                lastWasNothing = false;
                continue;
            }
            if (info.operation == Qt::IntersectClip) {
                region &= QRegion((info.path * matrix).toFillPolygon().toPolygon(),
                                  info.path.fillRule());
            } else if (info.operation == Qt::UniteClip) {
                region |= QRegion((info.path * matrix).toFillPolygon().toPolygon(),
                                  info.path.fillRule());
            } else if (info.operation == Qt::NoClip) {
                lastWasNothing = true;
                region = QRegion();
            } else {
                region = QRegion((info.path * matrix).toFillPolygon().toPolygon(),
                                 info.path.fillRule());
            }
            break;
        }
        }
    }

    return region;
}

/*!
    Returns the currently clip as a path. Note that the clip path is
    given in logical coordinates.

    \sa setClipPath(), clipRegion(), setClipping()
*/
QPainterPath QPainter::clipPath() const
{
    // ### Since we do not support path intersections and path unions yet,
    // we just use clipRegion() here...
    if (!isActive()) {
        qWarning("QPainter::clipPath: Painter not active");
        return QPainterPath();
    }

    Q_D(const QPainter);
    // No clip, return empty
    if (d->state->clipInfo.size() == 0) {
        return QPainterPath();
    } else {

        // Update inverse matrix, used below.
        if (!d->txinv)
            const_cast<QPainter *>(this)->d_ptr->updateInvMatrix();

        // For the simple case avoid conversion.
        if (d->state->clipInfo.size() == 1
            && d->state->clipInfo.at(0).clipType == QPainterClipInfo::PathClip) {
            QTransform matrix = (d->state->clipInfo.at(0).matrix * d->invMatrix);
            return d->state->clipInfo.at(0).path * matrix;

        // Fallback to clipRegion() for now, since we don't have isect/unite for paths
        } else {
            QPainterPath path;
            path.addRegion(clipRegion());
            return path;
        }
    }
}

/*!
    \fn void QPainter::setClipRect(const QRectF &rectangle, Qt::ClipOperation operation)

    Enables clipping, and sets the clip region to the given \a
    rectangle using the given clip \a operation. The default operation
    is to