QwtPlotMarker and scaling

Hello!

For example I have n markers in QwtPlot that are located horizontally...

And I want that this markers will be locate at coordinates: (x + 1*width(marker_1), Y) , (x + i * width(marker_i), Y) .... , (x + n *width(marker_n), Y). Where is x = 50 and Y = 100 - for example....

So I have some questions:
1. How I can get width and height of some marker with some text: "text + number of marker"?
2. When I will do scaling I'll have some space between markers. How I can take into account or how I can compute this space? I want that all my markers always paint without any spacing....

I hope U can give me some usefull advise.

Yours,
carhun

This is probably a different type of plot item, but no marker ( in the terminology of Qwt ).

What type of information do you want to display ?

Uwe

Hello, Uwe!

I want to display value of y that corresponds to pos.x(). And what i want to display must have some unique ( for all my "markers") background color and for example white color of pen ( font )...

So I have function that return me y = f(x) , where x = pos.x() and I want to display this with the condition that was described above...

Thanks

Youes,
carhun

All classes of the Qwt plot framework use QwtText instead of QString.

Beside the option of using different text engines ( pseudo-HTML, MathML ) each instance of QwtText has its individual attributes: font, pen and an optional background are among them.

But your second posting doesn't explain why you need the layout code of the first posting ?

Uwe

Yes, QwtText has it individual attributes that I need, but I cant say to QwtText - draw at (x,y)... For QwtPlotMarker I can do it with help of function someMarker->setValue(x, y)... So I need some class where I can write my QwtText and say where draw/write this text...

About your question I didnt understand it completely, but try to explain one more why I need to do like I write in first post:
I have N functions/graphics: f1(x) , f2(x), ..., fN(x). Then I have tracker that tell me pos.x() of mouse in the QwtPlot. And I want to display text that indicate value of fN(pos.x()), where is N = 1, ... N; And there is may be situation when two or more graphics will have same values of y = f1(x) = f2(x), so i need to display at point (pos.x(), y) - value of first function and at (pos.x() + width(QwtText/orsmth like this), y) - value of second function... I only want that they go always straight without any empty space between them...

I hope this explanation is more clear...

Yours,
carhun

Quote:

---

Originally Posted by carhun

Yes, QwtText has it individual attributes that I need, but I cant say to QwtText - draw at (x,y)... For QwtPlotMarker I can do it with help of function someMarker->setValue(x, y)...

---

Sure you can: QwtPlotMarker::setLabel( const QwtText& );

Quote:

---

Originally Posted by carhun

About your question I didnt understand it completely, but try to explain one more why I need to do like I write in first post: ...

---

So the code snippet was about how to avoid that marker labels overlap ?

Uwe

Quote:

---

Originally Posted by Uwe

So the code snippet was about how to avoid that marker labels overlap ?

---

In general situation - yes, how to avoid overlapping of the marker labels

Yours,
carhun

Quote:

---

Originally Posted by carhun

In general situation - yes, how to avoid overlapping of the marker labels

---

First of all you need to define your algorithm for a conflict resolution - Qwt doesn't offer one, basically because I don't know a satisfying general solution.

Then I can help with how to implement it with Qwt.

Uwe

I thought that algorithm will be next ( if I correctly understand about what conflicts you are talking ):
I have for example three point where I want to display my markers:
(2, 5), (4,5), (10,5).
So if we have the width of marker, we can check:
So I have interval (2, 2 + width) and I check with other X's of markers (4,10, etc ) and If some X's is in interval (2, 2 + width), so we have overlapping and i want to resolve this conflict in next for example way: the X value of second point [(4,5)] we set to 2 + width + 1...


Or I have some massive that contains value of Y and vector of X's that correspond to value Y:
In example above: 5 -> 2, 4, 10....
and then we need to display our markers in points: (2,5) (2+1*width, 5) (2 + 2*width, 5)


And so on for all markers...

Mb U have better solution?

Yours,
carhun

Quote:

---

Originally Posted by carhun

I have for example three point where I want to display my markers:
(2, 5), (4,5), (10,5).

---

The plot coordinates of the markers are of no importance - what you need are widget coordinates, f.e what you get when overloading QwtPlotMarker::drawLabel.

Code:

---

virtual void YourMarker::drawLabel( QPainter *painter,
    const QRectF &canvasRect, const QPointF &pos ) const
{
    const QSizeF labelSize = label().size( painter->font() );
 
    const QRectF rect = labelGeometry( pos, labelSize );
    label().draw( painter, rect );
}

---

Of course the problem now is how to implement YourMarker::labelGeometry(). A conflict resolution ( = avoid overlapping of marker labels ) needs to know position and size in widget coordinates of all markers.

Uwe

Idea I understand, if it will be some question about this topic Ill ask U:D

Thanks, Uwe

carhun

Hello, Uwe...

I want to ask U about background of label. I do smth like this:

Code:

---

const QSizeF labelSize = label().textSize(painter->font());
    const QRectF rect = labelGeometry(pos, labelSize);
 
    painter->save();
 
    painter->setPen(Qt::magenta);
    painter->setBrush(Qt::yellow);
 
    label().draw(painter, rect);
 
    painter->restore();

---

I also try to do smth like this instead of painter->set...(...):

Code:

---

label().setBackgroundBrush(Qt::yellow);

---

But text is shown correctly ( color = magenta ), but background - no ( background is white, not as I want f.e. yellow).
Can U tell me why? What I am doing wrong?

If i do smth like this, it is ok:

Code:

---

painter->fillRect(rect, m_labelBackgroundColor);

---

But is it good way?

carhun

Quote:

---

Originally Posted by carhun

Code:

---

label().setBackgroundBrush(Qt::yellow);

---

---

Your code assigns a background to a temporary copy of the label text object on the stack. Instead you have to write:

Code:

---

QwtText lbl = label();
lbl.setBackgroundBrush(Qt::yellow);
setLabel( lbl );

---

Uwe

Quote:

---

Originally Posted by Uwe

Your code assigns a background to a temporary copy of the label text object on the stack. Instead you have to write:

Code:

---

QwtText lbl = label();
lbl.setBackgroundBrush(Qt::yellow);
setLabel( lbl );

---

Uwe

---

It didn't help, results are same...

And I coudnt this do because drawLabel is const method...

Thanks, its work, but i need to do const_cast to do this:

Code:

---

const_cast<MyMarker *>(this)->setLabel(text);

---

carhun

Quote:

---

Originally Posted by carhun

And I coudnt this do because drawLabel is const method...

---

Of course this code is not intended to be inside of drawLabel - assign the background once not inside somewhere called below replot !

Uwe