How to draw text in QQuickItem?

maksim1979

if you use QQuickPaintedItem, you have to reimplement
@
virtual void paint(QPainter *painter) override;
@

This paint method will be called when you invoke update(); method

? Offline

We don't want to use QQuickPaintedItem, We want to use QQuickItem

? Offline

Thats the point, i have reimplemented paint, but i also have reimplemented updatePaintNode...
Maybe i have forgotten something in my reimplementation of updatePaintNode?

here is some code:

@MyQuickPaintedItem::MyQuickPaintedItem(QQuickItem *parent)
: QQuickPaintedItem(parent)
, m_xAxisLineCount(500)
{
setFlag(ItemHasContents, true);

setRenderTarget(QQuickPaintedItem::FramebufferObject);
setPerformanceHint(QQuickPaintedItem::FastFBOResizing);
setAntialiasing(true);
//setOpaquePainting(true);
setMipmap(true);
update();

}

QSGNode *MyQuickPaintedItem::updatePaintNode(QSGNode *oldNode, UpdatePaintNodeData *data)
{
QSGGeometryNode *node = 0;
QSGGeometry *geometry = 0;

if (!oldNode) {
    node = new QSGGeometryNode;

    geometry = new QSGGeometry(QSGGeometry::defaultAttributes_Point2D(), m_xAxisLineCount * 2);
    geometry->setLineWidth(1);
    geometry->setDrawingMode(GL_LINES);
    node->setGeometry(geometry);
    node->setFlag(QSGNode::OwnsGeometry);

    QSGFlatColorMaterial *material = new QSGFlatColorMaterial;
    material->setColor(QColor(255, 0, 0));
    node->setMaterial(material);
    node->setFlag(QSGNode::OwnsMaterial);

} else {
    node = static_cast<QSGGeometryNode *>(oldNode);
    geometry = node->geometry();
    geometry->allocate(m_xAxisLineCount * 2);
}

//qDebug("in updatePaintNode");

QRectF bounds = boundingRect();
QSGGeometry::Point2D *vertices = geometry->vertexDataAsPoint2D();


int iPlus = 0;

for (int i = 0; i <m_xAxisLineCount; ++i) {
    qreal t = i / qreal(m_xAxisLineCount - 1);

    vertices[iPlus].set(i, bounds.height() / 2.0);

    iPlus++;

// QPointF pos_amplitude (t, 0.8 );

// x = bounds.x() + pos_amplitude.x() * bounds.width();
// y = bounds.y() + pos_amplitude.y() * bounds.height();
int height = bounds.height();
int amplitude = rand() % height;
//int amplitude = height;

    vertices[iPlus].set(i, amplitude);
    iPlus++;
}
node->markDirty(QSGNode::DirtyGeometry);

return node;

}

void MyQuickPaintedItem::paint(QPainter *painter)
{
// // Pen
QColor randomColor(255,255,60);
QPen myPenRandomColor(randomColor);

QRectF bounds = contentsBoundingRect();

// Font
QFont font;
font.setFamily("Arial");
font.setPixelSize(20);
painter->setFont(font);

painter->setPen(myPenRandomColor);
qDebug("in paint");


painter->drawText(bounds,Qt::AlignCenter, "text");

}@@@@@

so if i take out the reimplementation of updatePaindNode, then the paint function is called...

some Idea how to call booth functions? i want to render text with the QPainter, but draw lines with QSG classes...

? Offline

[quote author="aabc" date="1410860899"]We don't want to use QQuickPaintedItem, We want to use QQuickItem[/quote]

I know, i also want to use QQuickItem, but i think if it is possible, then only with QQuickPaintedItem, if you have an idea, how to render text with QQuickItem, then is perfect, do you have?

greetings Tom

? Offline

reading the qt 5.4 documentation, and maybe the "QOpenGLWidget":http://doc-snapshot.qt-project.org/qt5-5.4/qopenglwidget.html#details
is a good way.
i read, that it is possible to construct a QPainter to draw primitives and render text...

"this":http://blog.qt.digia.com/blog/2014/09/10/qt-weekly-19-qopenglwidget/ is also a good article about the good old QGL classes, that i use in the moment... :-( because it is new for me, and unluckily it is old and deprecated...

? Offline

I think i found a way... :-)

here is a blog post how to render with QPainter in an QImage or FBO...
"http://dangelog.wordpress.com/2013/02/10/using-fbos-instead-of-pbuffers-in-qt-5-2/":http://dangelog.wordpress.com/2013/02/10/using-fbos-instead-of-pbuffers-in-qt-5-2/

With this you can make a FBO and render text with QPainter in it...

Then you take the FBO or the QImage and create a QSGSimpleTextureNode
"http://qt-project.org/doc/qt-5/qsgsimpletexturenode.html#setTexture":http://qt-project.org/doc/qt-5/qsgsimpletexturenode.html#setTexture

with setTexture you can set the texture to it... and just append the QSGSimpleTextureNode as child to your other node, and thats it :-) i hope...

I will try it on monday... and report if it works...

literA2

Hi, I'm having this problem also.

I need to render a text on my custom geometry, I don't want to use QPainter because of the blurry text issue in iOS (using QQuickPaintedItem class).

Please advise. TIA.

seyed

I need it too, because performance.
I looked at Qt's source code (qquicktextnode.cpp) and I found following lines. Perhaps it helps someone...

QSGGlyphNode *QQuickTextNode::addGlyphs(const QPointF &position, const QGlyphRun &glyphs, const QColor &color,
                                 QQuickText::TextStyle style, const QColor &styleColor,
                                 QSGNode *parentNode)
{
    QSGRenderContext *sg = QQuickItemPrivate::get(m_ownerElement)->sceneGraphRenderContext();
    QRawFont font = glyphs.rawFont();
    bool preferNativeGlyphNode = m_useNativeRenderer;
    if (!preferNativeGlyphNode) {
        QRawFontPrivate *fontPriv = QRawFontPrivate::get(font);
        if (fontPriv->fontEngine->hasUnreliableGlyphOutline())
            preferNativeGlyphNode = true;
        else
            preferNativeGlyphNode = !QFontDatabase().isSmoothlyScalable(font.familyName(), font.styleName());
    }

    QSGGlyphNode *node = sg->sceneGraphContext()->createGlyphNode(sg, preferNativeGlyphNode);

    node->setOwnerElement(m_ownerElement);
    node->setGlyphs(position + QPointF(0, glyphs.rawFont().ascent()), glyphs);
    node->setStyle(style);
    node->setStyleColor(styleColor);
    node->setColor(color);
    node->update();

    /* We flag the geometry as static, but we never call markVertexDataDirty
       or markIndexDataDirty on them. This is because all text nodes are
       discarded when a change occurs. If we start appending/removing from
       existing geometry, then we also need to start marking the geometry as
       dirty.
     */
    node->geometry()->setIndexDataPattern(QSGGeometry::StaticPattern);
    node->geometry()->setVertexDataPattern(QSGGeometry::StaticPattern);

    if (parentNode == 0)
        parentNode = this;
    parentNode->appendChildNode(node);

    return node;
}

devel

I'm making a custom QQuickItem too. And it needs to accept a delegate that'll appear in the specific position.

So, is it the right solution to expose a QRect property and do a QML wrapper that creates and positions that sub-item with a Loader?

Or it's somehow possible to attach other items directly to one of QSGNode of a custom QQuickItem?

vladstelmahovsky

@Alexey the only way is to use QQuickText and use private classes