qt5base-lts/examples/openvg/star/starwidget.cpp

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#include "starwidget.h"

StarWidget::StarWidget(QWidget *parent)
    : QWidget(parent)
    , path(VG_INVALID_HANDLE)
    , pen(Qt::red, 4.0, Qt::SolidLine, Qt::RoundCap, Qt::RoundJoin)
    , brush(Qt::yellow)
{
    setMinimumSize(220, 250);
    setSizePolicy(QSizePolicy::MinimumExpanding, QSizePolicy::MinimumExpanding);
}

static VGubyte const starSegments[] = {
    VG_MOVE_TO_ABS,
    VG_LINE_TO_REL,
    VG_LINE_TO_REL,
    VG_LINE_TO_REL,
    VG_LINE_TO_REL,
    VG_CLOSE_PATH
};
static VGfloat const starCoords[] = {
    110, 35,
    50, 160,
    -130, -100,
    160, 0,
    -130, 100
};

void StarWidget::paintEvent(QPaintEvent *)
{
    QPainter painter;
    painter.begin(this);

    // Make sure that we are using the OpenVG paint engine.
    if (painter.paintEngine()->type() != QPaintEngine::OpenVG) {
#ifdef Q_WS_QWS
        qWarning("Not using OpenVG: use the '-display' option to specify an OpenVG driver");
#else
        qWarning("Not using OpenVG: specify '-graphicssystem OpenVG'");
#endif
        return;
    }

    // Select a pen and a brush for drawing the star.
    painter.setPen(pen);
    painter.setBrush(brush);

    // We want the star border to be anti-aliased.
    painter.setRenderHints(QPainter::Antialiasing);

    // Flush the state changes to the OpenVG implementation
    // and prepare to perform raw OpenVG calls.
    painter.beginNativePainting();

    // Cache the path if we haven't already or if the path has
    // become invalid because the window's context has changed.
    if (path == VG_INVALID_HANDLE || !vgGetPathCapabilities(path)) {
        path = vgCreatePath(VG_PATH_FORMAT_STANDARD,
                            VG_PATH_DATATYPE_F,
                            1.0f, // scale
                            0.0f, // bias
                            6,    // segmentCapacityHint
                            10,   // coordCapacityHint
                            VG_PATH_CAPABILITY_ALL);
        vgAppendPathData(path, sizeof(starSegments), starSegments, starCoords);
    }

    // Draw the star directly using the OpenVG API.
    vgDrawPath(path, VG_FILL_PATH | VG_STROKE_PATH);

    // Restore normal QPainter operations.
    painter.endNativePainting();

    painter.end();
}