qt-everywhere-src-5.15.1/qtdeclarative/examples/quick/scenegraph/rendernode/softwarerenderer.cpp

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#include "softwarerenderer.h"
#include <QQuickItem>
#include <QQuickWindow>
#include <QSGRendererInterface>
#include <QPainter>
#include <QPainterPath>

SoftwareRenderNode::~SoftwareRenderNode()
{
    releaseResources();
}

void SoftwareRenderNode::releaseResources()
{
}

void SoftwareRenderNode::render(const RenderState *renderState)
{
    Q_ASSERT(m_window);

    QSGRendererInterface *rif = m_window->rendererInterface();
    QPainter *p = static_cast<QPainter *>(rif->getResource(m_window, QSGRendererInterface::PainterResource));
    Q_ASSERT(p);

    const QRegion *clipRegion = renderState->clipRegion();
    if (clipRegion && !clipRegion->isEmpty())
        p->setClipRegion(*clipRegion, Qt::ReplaceClip); // must be done before setTransform

    p->setTransform(matrix()->toTransform());
    p->setOpacity(inheritedOpacity());

    const QPointF p0(m_width - 1, m_height - 1);
    const QPointF p1(0, 0);
    const QPointF p2(0, m_height - 1);
    QPainterPath path(p0);
    path.lineTo(p1);
    path.lineTo(p2);
    path.closeSubpath();

    QLinearGradient gradient(QPointF(0, 0), QPointF(m_width, m_height));
    gradient.setColorAt(0, Qt::green);
    gradient.setColorAt(1, Qt::red);

    p->fillPath(path, gradient);
}

QSGRenderNode::StateFlags SoftwareRenderNode::changedStates() const
{
    return {};
}

QSGRenderNode::RenderingFlags SoftwareRenderNode::flags() const
{
    return BoundedRectRendering;
}

QRectF SoftwareRenderNode::rect() const
{
    return QRect(0, 0, m_width, m_height);
}

void SoftwareRenderNode::sync(QQuickItem *item)
{
    m_window = item->window();
    m_width = item->width();
    m_height = item->height();
}