problem in QLinef()

hi friends ,
i need a help to clarify my doubt in QLineF() .. i dont know where i am commiting the mistake ..

in mainwindow.cpp (QGraphicsView())
i create a line item class ....

Code:

---

line1 = new LineItem(QLineF(2,4, 132 ,160), Qt::blue);
        line1->setPos(374,215);

---

and
in lineitem.cpp

Code:

---

LineItem::LineItem(const QLineF &line, const Qt::GlobalColor color)
         : QGraphicsLineItem(line),
                color(color)
 
void LineItem ::paint(QPainter *painter, const QStyleOptionGraphicsItem *option, QWidget *)
{
         painter->setPen(QColor(color));
       QReal  value = 90;
        line().setAngle(value);
        painter->drawLine(line());
}

---

here the line is drawn perfectly but i cant fix the angle ... its not turning in counter clockwise ... not like transform.rotate .. why ?

please help ...

You shouldn't change the angle like that. The paint() routine should always paint the item the same way, regardless of its actual position or rotation on the scene. If you want to rotate the line, use rotate() on the item, but still draw the item as if it was in its original direction (i.e. horizontal).

Quote:

---

Originally Posted by wysota

You shouldn't change the angle like that. The paint() routine should always paint the item the same way, regardless of its actual position or rotation on the scene. If you want to rotate the line, use rotate() on the item, but still draw the item as if it was in its original direction (i.e. horizontal).

---

thanks for reply ..
transform.rotate(90) is working fine ... but how can i use this QLineF::setAngle() function ... where can i implement it ..

hi friends,
i try using QTransform as

in mainwindow.cpp (GraphicsView())

Code:

---

line1 = new LineItem(QLineF(2,4, 132 ,160), Qt::blue, 90);   //creating an lineItem in scene
    line1->setPos(374,215);                        //settting the line position in screen
    scene->addItem(line1);

---

in lineitem.cpp

Code:

---

LineItem::LineItem(const QLineF &line, const Qt::GlobalColor color, qreal angle)
         : QGraphicsLineItem(line),
                color(color)                                                                        //constuctor
{
       qreal value = angle;    
}

---

Code:

---

void LineItem ::paint(QPainter *painter, const QStyleOptionGraphicsItem *option, QWidget *)
{
         QTransform transform;
          painter->setPen(QColor(color));
       if(value){
             transform.translate(300,300);              // here comes the problem
             transform.rotate(value);
             painter->setTransform(transform);
             painter->drawLine(line());
             }else{
              line().setAngle(value);
              painter->drawLine(line());
           }
}

---

in this program if the user send the the angle of rotation the line with the same coordinates i try to rotate ... but without this
transform.translate(x,y); i cant see the line ... more the

Code:

---

line1->setPos(374,215);          // graphicasScene

---

this value also not working .. why ? it is defaulter to top left of the screen ...

but if there is no angle argument like

Code:

---

line1 = new LineItem(QLineF(2,4, 132 ,160), Qt::blue );    //without angle argument

---

its working fine ... i can setPos() the item ... why? ..

please help

Quote:

---

Originally Posted by wagmare

but how can i use this QLineF::setAngle() function ... where can i implement it ..

---

Don't use it with QGraphicsLineItem, it doesn't make much sense to do so in this context. Rotate the item, not the line within it.

thanks .. i will rotate the item as

Code:

---

QTransform transform;
        transform.rotate(90);
          line1 = new LineItem(QLineF(1,1, 132 ,160), Qt::blue, 90);
        scene->addItem(line1);
        line1->setPos(574,415);
        line1->setTransform(transform);

---