Rotate items in qwt

[jesse_mark]

im new to qwt

i want to draw a grid in qwt, where it will look like a Rect (x1,y1, x2,y2, x3,y3,x4,y4) ... then i want to rotate it with a specific angle.

so can anybody please help how can we rotate items in qwt is there any function such as QRect.rotate ("angle").
and is the there a Rect item in qwt or i have to draw each line by it self.

[Uwe]

i want to draw a grid in qwt, where it will look like a Rect (x1,y1, x2,y2, x3,y3,x4,y4) ... then i want to rotate it with a specific angle.

What type of coordinates are these: plot or widget coordinates ?

so can anybody please help how can we rotate items in qwt is there any function such as QRect.rotate ("angle").

Use QTransform.

and is the there a Rect item in qwt or i have to draw each line by it self.

In the navigation example you find a plot item, that displays a rectangle. The next version of Qwt ( available in SVN trunk ) will offer QwtPlotShapeItem, that displays any type of shape, that can be expressed by a QPainterPath - what includes a rectangle.

The idea behind plot items is, that they will be mapped and displayed on the plot canvas according to the coordinate system of the axes. This mapping needs a translation and scaling, but no rotation. So this needs to be done inside the implementation of a plot item.

Uwe

[jesse_mark]

What type of coordinates are these: plot or widget coordinates ?

im using plot coordinates and im usgin qwtcurve and give setdata and this is a snipt of the code ... it draw the rectangle

QwtPlotCurve *curve1 = new QwtPlotCurve("Curve 1");
QwtPointSeriesData* myData = new QwtPointSeriesData;
QVector<QPointF>* samples = new QVector<QPointF>;
samples->push_back(QPointF(1000,1000)); // my origin
samples->push_back(newPosition(100,100,8200,1000,-30));
samples->push_back(newPosition(100,100,8200,8200,-30));
samples->push_back(newPosition(100,100,1000,8200,-30));
samples->push_back(QPointF(1000,1000));
myData->setSamples(*samples);
curve1->setData(myData);

curve1->setBrush(mybrush);

curve1->setPen(p);

curve1->attach(ui->qwtPlot);

Use QTransform.

do you mind tell me how can i use QTransform with qwtcurve ??

thank you so much

[Uwe]

do you mind tell me how can i use QTransform with qwtcurve ??

You can't - but you can use QTransform to rotate a rectangle ( or any other polygon ):

QTransform transform;
transform.translate( rect.topLeft() ); // origin of your rotation
transform.rotate( ... );
 
QPolygonF points = transform.mapToPolygon( QRectF( 0, 0, rect.width(), rect.height() );
 
...

QTransform transform;
transform.translate( rect.topLeft() ); // origin of your rotation
transform.rotate( ... );

QPolygonF points = transform.mapToPolygon( QRectF( 0, 0, rect.width(), rect.height() );

...

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It's up to you to decide if this makes your code easier.

Uwe

[jesse_mark]

but how can i display the QPolygon on qwtpolt after that ??

[Uwe]

but how can i display the QPolygon on qwtpolt after that ??

The same way like in your code above - or even easier this way:

curve1->setSamples( polygon );

curve1->setSamples( polygon );

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Uwe

[jesse_mark]

[QUOTE=Uwe;224305]

QPolygonF points = transform.mapToPolygon( QRectF( 0, 0, rect.width(), rect.height() );

QPolygonF points = transform.mapToPolygon( QRectF( 0, 0, rect.width(), rect.height() );

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i used QRect as there is no transform.mapToPolygon takes QRectF

this is what i wrote :

QRect grid;
           grid.setTop(Ox);
           grid.setLeft(Oy);
           grid.setHeight(Hight);
           grid.setWidth(Width);
 
 
           QTransform Tr;
           Tr.translate(grid.top(),grid.left()); 
           Tr.rotate(30);
 
          QPolygonF points = Tr.mapToPolygon(QRect(0, 0, grid.width(), grid.height()));
 
curve1->setSamples( points );

QRect grid;
           grid.setTop(Ox);
           grid.setLeft(Oy);
           grid.setHeight(Hight);
           grid.setWidth(Width);


           QTransform Tr;
           Tr.translate(grid.top(),grid.left()); 
           Tr.rotate(30);

          QPolygonF points = Tr.mapToPolygon(QRect(0, 0, grid.width(), grid.height()));

curve1->setSamples( points );

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but the resulted graph was not rectangle it was

qwt.jpeg

[Uwe]

It is a rectangle, but setting a curve brush means that the area below the points ( to the baseline ) is filled - not the area inside the polygon.

But I already told you in my first answer what type of plot item you need. I recommend to copy the RectItem of the navigation example and modify it so that it works with polygons. In the draw method you have to transform the points of the polygon one by one ( instead of a rectangle once ).

Another option is to keep the RectItem as it is, beside rotating the translated rectangle inside of the draw method - but I don't know your use case.

Uwe