path: root/src/declarative/items/qsgpainteditem.cpp

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#include "qsgpainteditem.h"
#include <private/qsgpainteditem_p.h>
#include <private/qsgpainternode_p.h>

#include <private/qsgcontext_p.h>
#include <private/qsgadaptationlayer_p.h>
#include <qmath.h>

QT_BEGIN_NAMESPACE

/*!
    \class QSGPaintedItem
    \brief The QSGPaintedItem class provides a way to use the QPainter API in the
    QML Scene Graph.

    The QSGPaintedItem makes it possible to use the QPainter API with the QML Scene Graph.
    It sets up a textured rectangle in the Scene Graph and uses a QPainter to paint
    onto the texture. The render target can be either a QImage or a QGLFramebufferObject.
    When the render target is a QImage, QPainter first renders into the image then
    the content is uploaded to the texture.
    When a QGLFramebufferObject is used, QPainter paints directly onto the texture.
    Call update() to trigger a repaint.

    To enable QPainter to do anti-aliased rendering, use setAntialiasing().

    QSGPaintedItem is meant to make it easier to port old code that is using the
    QPainter API to the QML Scene Graph API and it should be used only for that purpose.

    To write your own painted item, you first create a subclass of QSGPaintedItem, and then
    start by implementing its only pure virtual public function: paint(), which implements
    the actual painting. To get the size of the area painted by the item, use
    contentsBoundingRect().
*/

/*!
    \enum QSGPaintedItem::RenderTarget

    This enum describes QSGPaintedItem's render targets. The render target is the
    surface QPainter paints onto before the item is rendered on screen.

    \value Image The default; QPainter paints into a QImage using the raster paint engine.
    The image's content needs to be uploaded to graphics memory afterward, this operation
    can potentially be slow if the item is large. This render target allows high quality
    anti-aliasing and fast item resizing.

    \value FramebufferObject QPainter paints into a QGLFramebufferObject using the GL
    paint engine. Painting can be faster as no texture upload is required, but anti-aliasing
    quality is not as good as if using an image. This render target allows faster rendering
    in some cases, but you should avoid using it if the item is resized often.

    \sa setRenderTarget()
*/

/*!
    \internal
*/
QSGPaintedItemPrivate::QSGPaintedItemPrivate()
    : QSGItemPrivate()
    , contentsScale(1.0)
    , fillColor(Qt::transparent)
    , renderTarget(QSGPaintedItem::Image)
    , geometryDirty(false)
    , contentsDirty(false)
    , opaquePainting(false)
    , antialiasing(false)
    , mipmap(false)
{
}

/*!
    Constructs a QSGPaintedItem with the given \a parent item.
 */
QSGPaintedItem::QSGPaintedItem(QSGItem *parent)
    : QSGItem(*(new QSGPaintedItemPrivate), parent)
{
    setFlag(ItemHasContents);
}

/*!
    \internal
*/
QSGPaintedItem::QSGPaintedItem(QSGPaintedItemPrivate &dd, QSGItem *parent)
    : QSGItem(dd, parent)
{
    setFlag(ItemHasContents);
}

/*!
    Destroys the QSGPaintedItem.
*/
QSGPaintedItem::~QSGPaintedItem()
{
}

/*!
    Schedules a redraw of the area covered by \a rect in this item. You can call this function
    whenever your item needs to be redrawn, such as if it changes appearance or size.

    This function does not cause an immediate paint; instead it schedules a paint request that
    is processed by the QML Scene Graph when the next frame is rendered. The item will only be
    redrawn if it is visible.

    Note that calling this function will trigger a repaint of the whole scene.

    \sa paint()
*/
void QSGPaintedItem::update(const QRect &rect)
{
    Q_D(QSGPaintedItem);
    d->contentsDirty = true;

    QRect srect(qCeil(rect.x()*d->contentsScale),
            qCeil(rect.y()*d->contentsScale),
            qCeil(rect.width()*d->contentsScale),
            qCeil(rect.height()*d->contentsScale));

    if (srect.isNull() && !d->dirtyRect.isNull())
        d->dirtyRect = contentsBoundingRect().toAlignedRect();
    else
        d->dirtyRect |= (contentsBoundingRect() & srect).toAlignedRect();
    QSGItem::update();
}

/*!
    Returns true if this item is opaque; otherwise, false is returned.

    By default, painted items are not opaque.

    \sa setOpaquePainting()
*/
bool QSGPaintedItem::opaquePainting() const
{
    Q_D(const QSGPaintedItem);
    return d->opaquePainting;
}

/*!
    If \a opaque is true, the item is opaque; otherwise, it is considered as translucent.

    Opaque items are not blended with the rest of the scene, you should set this to true
    if the content of the item is opaque to speed up rendering.

    By default, painted items are not opaque.

    \sa opaquePainting()
*/
void QSGPaintedItem::setOpaquePainting(bool opaque)
{
    Q_D(QSGPaintedItem);

    if (d->opaquePainting == opaque)
        return;

    d->opaquePainting = opaque;
    QSGItem::update();
}

/*!
    Returns true if antialiased painting is enabled; otherwise, false is returned.

    By default, antialiasing is not enabled.

    \sa setAntialiasing()
*/
bool QSGPaintedItem::antialiasing() const
{
    Q_D(const QSGPaintedItem);
    return d->antialiasing;
}

/*!
    If \a enable is true, antialiased painting is enabled.

    By default, antialiasing is not enabled.

    \sa antialiasing()
*/
void QSGPaintedItem::setAntialiasing(bool enable)
{
    Q_D(QSGPaintedItem);

    if (d->antialiasing == enable)
        return;

    d->antialiasing = enable;
    update();
}

/*!
    Returns true if mipmaps are enabled; otherwise, false is returned.

    By default, mipmapping is not enabled.

    \sa setMipmap()
*/
bool QSGPaintedItem::mipmap() const
{
    Q_D(const QSGPaintedItem);
    return d->mipmap;
}

/*!
    If \a enable is true, mipmapping is enabled on the associated texture.

    Mipmapping increases rendering speed and reduces aliasing artifacts when the item is
    scaled down.

    By default, mipmapping is not enabled.

    \sa mipmap()
*/
void QSGPaintedItem::setMipmap(bool enable)
{
    Q_D(QSGPaintedItem);

    if (d->mipmap == enable)
        return;

    d->mipmap = enable;
    update();
}

/*!
    This function returns the outer bounds of the item as a rectangle; all painting must be
    restricted to inside an item's bounding rect.

    If the contents size has not been set it reflects the size of the item; otherwise
    it reflects the contents size scaled by the contents scale.

    Use this function to know the area painted by the item.

    \sa QSGItem::width(), QSGItem::height(), contentsSize(), contentsScale()
*/
QRectF QSGPaintedItem::contentsBoundingRect() const
{
    Q_D(const QSGPaintedItem);

    qreal w = d->width;
    QSizeF sz = d->contentsSize * d->contentsScale;
    if (w < sz.width())
        w = sz.width();
    qreal h = d->height;
    if (h < sz.height())
        h = sz.height();

    return QRectF(0, 0, w, h);
}

/*!
    \property QSGPaintedItem::contentsSize
    \brief The size of the contents

    The contents size is the size of the item in regards to how it is painted
    using the paint() function.  This is distinct from the size of the
    item in regards to height() and width().
*/
QSize QSGPaintedItem::contentsSize() const
{
    Q_D(const QSGPaintedItem);
    return d->contentsSize;
}

void QSGPaintedItem::setContentsSize(const QSize &size)
{
    Q_D(QSGPaintedItem);

    if (d->contentsSize == size)
        return;

    d->contentsSize = size;
    update();
}

/*!
    This convenience function is equivalent to calling setContentsSize(QSize()).
*/
void QSGPaintedItem::resetContentsSize()
{
    setContentsSize(QSize());
}

/*!
    \property QSGPaintedItem::contentsScale
    \brief The scale of the contents

    All painting happening in paint() is scaled by the contents scale. This is distinct
    from the scale of the item in regards to scale().

    The default value is 1.
*/
qreal QSGPaintedItem::contentsScale() const
{
    Q_D(const QSGPaintedItem);
    return d->contentsScale;
}

void QSGPaintedItem::setContentsScale(qreal scale)
{
    Q_D(QSGPaintedItem);

    if (d->contentsScale == scale)
        return;

    d->contentsScale = scale;
    update();
}

/*!
    \property QSGPaintedItem::fillColor
    \brief The item's background fill color.

    By default, the fill color is set to Qt::transparent.
*/
QColor QSGPaintedItem::fillColor() const
{
    Q_D(const QSGPaintedItem);
    return d->fillColor;
}

void QSGPaintedItem::setFillColor(const QColor &c)
{
    Q_D(QSGPaintedItem);

    if (d->fillColor == c)
        return;

    d->fillColor = c;
    update();

    emit fillColorChanged();
}

/*!
    \property QSGPaintedItem::renderTarget
    \brief The item's render target.

    This property defines which render target the QPainter renders into, it can be either
    QSGPaintedItem::Image or QSGPaintedItem::FramebufferObject. Both have certains benefits,
    typically performance versus quality. Using a framebuffer object avoids a costly upload
    of the image contents to the texture in graphics memory, while using an image enables
    high quality anti-aliasing.

    \warning Resizing a framebuffer object is a costly operation, avoid using
    the QSGPaintedItem::FramebufferObject render target if the item gets resized often.

    By default, the render target is QSGPaintedItem::Image.
*/
QSGPaintedItem::RenderTarget QSGPaintedItem::renderTarget() const
{
    Q_D(const QSGPaintedItem);
    return d->renderTarget;
}

void QSGPaintedItem::setRenderTarget(RenderTarget target)
{
    Q_D(QSGPaintedItem);

    if (d->renderTarget == target)
        return;

    d->renderTarget = target;
    update();

    emit renderTargetChanged();
}

/*!
    \fn virtual void QSGPaintedItem::paint(QPainter *painter) = 0

    This function, which is usually called by the QML Scene Graph, paints the
    contents of an item in local coordinates.

    The function is called after the item has been filled with the fillColor.

    Reimplement this function in a QSGPaintedItem subclass to provide the
    item's painting implementation, using \a painter.

    \note The QML Scene Graph uses two separate threads, the main thread does things such as
    processing events or updating animations while a second thread does the actual OpenGL rendering.
    As a consequence, paint() is not called from the main GUI thread but from the GL enabled
    renderer thread. At the moment paint() is called, the GUI thread is blocked and this is
    therefore thread-safe.
*/

/*!
    This function is called after the item's geometry has changed.
*/
void QSGPaintedItem::geometryChanged(const QRectF &newGeometry, const QRectF &oldGeometry)
{
    Q_D(QSGPaintedItem);
    d->geometryDirty = true;
    QSGItem::geometryChanged(newGeometry, oldGeometry);
}


/*!
    This function is called when the Scene Graph node associated to the item needs to
    be updated.
*/
QSGNode *QSGPaintedItem::updatePaintNode(QSGNode *oldNode, UpdatePaintNodeData *data)
{
    Q_UNUSED(data);
    Q_D(QSGPaintedItem);

    if (width() <= 0 || height() <= 0) {
        delete oldNode;
        return 0;
    }

    QSGPainterNode *node = static_cast<QSGPainterNode *>(oldNode);
    if (!node)
        node = new QSGPainterNode(this);

    QRectF br = contentsBoundingRect();

    node->setPreferredRenderTarget(d->renderTarget);
    node->setSize(QSize(qRound(br.width()), qRound(br.height())));
    node->setSmoothPainting(d->antialiasing);
    node->setLinearFiltering(d->smooth);
    node->setMipmapping(d->mipmap);
    node->setOpaquePainting(d->opaquePainting);
    node->setFillColor(d->fillColor);
    node->setContentsScale(d->contentsScale);
    node->setDirty(d->contentsDirty || d->geometryDirty, d->dirtyRect);
    node->update();

    d->contentsDirty = false;
    d->geometryDirty = false;
    d->dirtyRect = QRect();

    return node;
}

QT_END_NAMESPACE