QGraphicsText Item Rotation and antialiasing

[yogeshupreti]

Dear All,
I have Antialiasing problem with the rotated text in QGraphicsView. I have found some bugs regarding the same problem and I have tried the latest Qt Version (5.0.0 RC2), but the problem is still not Fixed. Does someone know a workaround?
I have the following code:

class FieldBoundText : public QGraphicsTextItem
{
    Q_OBJECT
public:
    /*!
      Class initializer,
        - str: supply a string to display
    */
    FieldBoundText(QString str, QGraphicsItem * parent = 0);

class FieldBoundText : public QGraphicsTextItem
{
    Q_OBJECT
public:
    /*!
      Class initializer,
        - str: supply a string to display
    */
    FieldBoundText(QString str, QGraphicsItem * parent = 0);

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and have re-implemented the paint function for the class to add Anti-Aliasing:

protected:
    /*!
      Reimplementing painter class for Antialiasing the font
    */
    void paint(QPainter *painter, const QStyleOptionGraphicsItem *option, QWidget *widget);

protected:
    /*!
      Reimplementing painter class for Antialiasing the font
    */
    void paint(QPainter *painter, const QStyleOptionGraphicsItem *option, QWidget *widget);

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Which looks like:

void FieldBoundText::paint(QPainter *painter, const QStyleOptionGraphicsItem *option, QWidget *widget){
    painter->setRenderHints(QPainter::Antialiasing|QPainter::TextAntialiasing);
    QGraphicsTextItem::paint(painter,option,widget);
}

void FieldBoundText::paint(QPainter *painter, const QStyleOptionGraphicsItem *option, QWidget *widget){
    painter->setRenderHints(QPainter::Antialiasing|QPainter::TextAntialiasing);
    QGraphicsTextItem::paint(painter,option,widget);
}

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Implementing the code like:

FieldBoundText  *txt = new FieldBoundText(QString("%1").arg(corner));
            txt->setPos(xStart,0);
            txt->setRotation(-45.0);

FieldBoundText  *txt = new FieldBoundText(QString("%1").arg(corner));
            txt->setPos(xStart,0);
            txt->setRotation(-45.0);

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Results in the text without Anti-aliasing :
No-Anti-Aliasing.JPG

Please let me know if there is some work around for this problem?

- Yogesh Upreti

[Jonny174]

In your QGraphicsView

setRenderHints( QPainter::Antialiasing | QPainter::SmoothPixmapTransform );

setRenderHints( QPainter::Antialiasing | QPainter::SmoothPixmapTransform );

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new QGLWidget( QGLFormat( QGL::SampleBuffers | QGL::AlphaChannel | QGL::Rgba ) );
 
QGLFormat frm = wgt->format();
frm.setSamples(4);

new QGLWidget( QGLFormat( QGL::SampleBuffers | QGL::AlphaChannel | QGL::Rgba ) );

QGLFormat frm = wgt->format();
frm.setSamples(4);

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[d_stranz]

QGLFormat frm = wgt->format();
frm.setSamples(4);

"frm" is a copy of the widget's QGLFormat. Don't you need to call QGLWidget::setFormat() method before these changes will have any effect on the widget?

[yogeshupreti]

Hello Jonny,
I have already Antialiasing on in my QGraphicsView

I have following on :
QPainter::Antialiasing, QPainter::TextAntialiasing, QPainter::HighQualityAntialiasing

But still no effect.

Although I am not sure what QGLFormat have to do with this??

In your QGraphicsView

setRenderHints( QPainter::Antialiasing | QPainter::SmoothPixmapTransform );

setRenderHints( QPainter::Antialiasing | QPainter::SmoothPixmapTransform );

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new QGLWidget( QGLFormat( QGL::SampleBuffers | QGL::AlphaChannel | QGL::Rgba ) );
 
QGLFormat frm = wgt->format();
frm.setSamples(4);

new QGLWidget( QGLFormat( QGL::SampleBuffers | QGL::AlphaChannel | QGL::Rgba ) );

QGLFormat frm = wgt->format();
frm.setSamples(4);

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[wysota]

Please provide a minimal compilable example reproducing the problem.