erratic behavior of graphics items

[sajis997]

I call the prepareGeometryhange() inside the definition of boundary rectangle but it gives me the error as follows:

RootGraphicsItem.cpp:668: error: passing ‘const RootGraphicsItem’ as ‘this’ argument of ‘void QGraphicsItem::prepareGeometryChange()’ discards qualifiers

RootGraphicsItem.cpp:668: error: passing ‘const RootGraphicsItem’ as ‘this’ argument of ‘void QGraphicsItem::prepareGeometryChange()’ discards qualifiers

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I guess that it is not the right place to call the prepareGeometryChange(), as i am doing it now:

QRectF RootGraphicsItem::boundingRect() const
{
 
    prepareGeometryChange();
 
    //!get the bounding rectangle of the enclosing text
    QRectF rect = m_textGraphicsItem->boundingRect();
 
    //the following condition decides if the boundary needs
    //to be changed
    if( rect.width() < m_drawRectMinimumWidth )
        rect.setWidth(m_drawRectMinimumWidth);
 
    if(rect.height() < m_drawRectMinimumHeight)
        rect.setHeight(m_drawRectMinimumHeight);
 
    //set the rectangle width with the text item spacing
    rect.setWidth(rect.width() + getTextItemSpacing() );
 
    //and return the rectangle
    return rect;
}

QRectF RootGraphicsItem::boundingRect() const
{

    prepareGeometryChange();

    //!get the bounding rectangle of the enclosing text
    QRectF rect = m_textGraphicsItem->boundingRect();

    //the following condition decides if the boundary needs
    //to be changed
    if( rect.width() < m_drawRectMinimumWidth )
        rect.setWidth(m_drawRectMinimumWidth);

    if(rect.height() < m_drawRectMinimumHeight)
        rect.setHeight(m_drawRectMinimumHeight);

    //set the rectangle width with the text item spacing
    rect.setWidth(rect.width() + getTextItemSpacing() );

    //and return the rectangle
    return rect;
}

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According to the manual it should be called once the set bounding rectangle is about to change. I am deciding the size before setting the bounding rectangle.

Any more suggestion ?

[wysota]

Calling that method from within boundingRect() wouldn't make sense. You need to call it when the actual change occurs (like when the text or spacing is changed).

[sajis997]

Hi

This is what i think as well. I am changing the text later after defining the bounding rectangle.


Could you please figure out any another reason that the arrow item and elliptical item intersection test is not functioning ?



Regards
Sajjad

[wysota]

Could you please figure out any another reason that the arrow item and elliptical item intersection test is not functioning ?

What's wrong with the original reason? Don't you think we should test one thing at a time?

[sajis997]

Hi

I am sorry. I did not get your last post. Did i cause something to distract from the main issue here. Let me summarize again:

I am trying to make connections between arrow and elliptical items in my own project and i tried to use the concept of diagramscene example.

I am having trouble to implement it - as the arrow is not properly attached to the elliptical items and they suddenly disappear once i start to move the elliptical items in the scene view.

I recreated the problem in the diagram scene example and posted in the forum for your point of view. All the details are mentioned in the previous posts.

Now please guide me where should i start from to debug this problem ?


Regards
Sajjad

[wysota]

Hi

I am sorry. I did not get your last post. Did i cause something to distract from the main issue here. Let me summarize again:

I am trying to make connections between arrow and elliptical items in my own project and i tried to use the concept of diagramscene example.

I am having trouble to implement it - as the arrow is not properly attached to the elliptical items and they suddenly disappear once i start to move the elliptical items in the scene view.

I recreated the problem in the diagram scene example and posted in the forum for your point of view. All the details are mentioned in the previous posts.

Now please guide me where should i start from to debug this problem ?

Correct the bounding rect issue as it may have influence on how your scene is rendered in the view. Once that is done and it's not something that causes the misbehaviour, we can look elsewhere. Otherwise you can prepare a minimal compilable example reproducing the problem and we can work on that.

[sajis997]

Hi

I would like to know what do i have to do to correct the bounding rect issue of the elliptical graphics item. Its bounding rectangle is based on the bounding rectangle of the text graphics item it contains. Text graphics item that is contained inside the elliptical item is in turn the subclass of QTextGraphicsItem. I would like to repeat that once that the bounding rect is defined inside the boundingRect() it is never changed since then and this is why i do not see any reason to call the prepareGeometryChange() function.

Could you please mention what might be wrong in the bounding rect function

QRectF RootGraphicsItem::boundingRect() const
{
 
    prepareGeometryChange();
 
    //!get the bounding rectangle of the enclosing text
    QRectF rect = m_textGraphicsItem->boundingRect();
 
    //the following condition decides if the boundary needs
    //to be changed
    if( rect.width() < m_drawRectMinimumWidth )
        rect.setWidth(m_drawRectMinimumWidth);
 
    if(rect.height() < m_drawRectMinimumHeight)
        rect.setHeight(m_drawRectMinimumHeight);
 
    //set the rectangle width with the text item spacing
    rect.setWidth(rect.width() + getTextItemSpacing() );
 
    //and return the rectangle
    return rect;
}

QRectF RootGraphicsItem::boundingRect() const
{

    prepareGeometryChange();

    //!get the bounding rectangle of the enclosing text
    QRectF rect = m_textGraphicsItem->boundingRect();

    //the following condition decides if the boundary needs
    //to be changed
    if( rect.width() < m_drawRectMinimumWidth )
        rect.setWidth(m_drawRectMinimumWidth);

    if(rect.height() < m_drawRectMinimumHeight)
        rect.setHeight(m_drawRectMinimumHeight);

    //set the rectangle width with the text item spacing
    rect.setWidth(rect.width() + getTextItemSpacing() );

    //and return the rectangle
    return rect;
}

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Otherwise i am attaching the files again which is compilable that recreates the problem in another project. All that you need to do is that create another copy of the diagramscene example, remove the diagramscene.h and diagramscene.cpp and add the following files:

diagramsceneview.h
diagramsceneview.cpp
diagramitem.h
diagramitem.cpp

And you have add the following line inside the createToolBox() of mainwindow.cpp

layout->addWidget(createCellWidget(tr("Ellipse"),DiagramItem::Ellipse),2,0);

layout->addWidget(createCellWidget(tr("Ellipse"),DiagramItem::Ellipse),2,0);

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If you mange some time and compile with these added files and the reamaining files as arrived with the example you will see the problem

The arrow is not connected as it is supposed to .


Let me know if you have any trouble to compile them .


Regards
Sajjad

[wysota]

And what should I be looking at once I start the program? What exactly did you change in those files?

[sajis997]

Hello ,

Create Two elliptical items in the scene and connect them with a line. Line drawing can be done in one of the two ways. Either you use the one that came along with the original diagram scene example or the one i have added - move the the mouse with the control modifier and the line will be drawn. When you release the control modifier
it will do the usual checking if there is any item under the event position and take the steps to draw the line arrow or not.

Once the items are connected, try to move the elliptical items and then you will see the problem - the arrow is not properly attached to the elliptical items and at times the arrow disappears.


I have removed the diagramscene.h - which was a subclass of QGraphicsScene, instead i have created a class called diagramsceneview - a subclass of QGraphicsView and moved all the functionalities to this class here. You have to remove the diagramscene class from your copy of the diagramscene example as well and add the one i have attached.

Then you have to make the following changes inside th diagramitem.h file

enum DiagramType
    {
       Step,
       Conditional,
       StartEnd,
       Io ,
       Ellipse // add the ellipse type
    };

enum DiagramType
    {
       Step,
       Conditional,
       StartEnd,
       Io ,
       Ellipse // add the ellipse type
    };

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In the constructor of diagramitem.cpp do the following:

case Ellipse:
            {
                //declare an ellipse with the bounding rectange
//                QGraphicsEllipseItem item(-100,-50,200,100);
                QGraphicsEllipseItem item(0,0,200,100);
                myPolygon = item.shape().toFillPolygon();
            }
            break;

case Ellipse:
            {
                //declare an ellipse with the bounding rectange
//                QGraphicsEllipseItem item(-100,-50,200,100);
                QGraphicsEllipseItem item(0,0,200,100);
                myPolygon = item.shape().toFillPolygon();
            }
            break;

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And at last in the createToolBox() function of mainwindow.cpp add the following:

layout->addWidget(createCellWidget(tr("Ellipse"),DiagramItem::Ellipse),2,0);

layout->addWidget(createCellWidget(tr("Ellipse"),DiagramItem::Ellipse),2,0);

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So you are good to compile and run and see the problem, the problem is because of the following

//                QGraphicsEllipseItem item(-100,-50,200,100);
                QGraphicsEllipseItem item(0,0,200,100);

//                QGraphicsEllipseItem item(-100,-50,200,100);
                QGraphicsEllipseItem item(0,0,200,100);

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As you can see that i have commented the first line to recreate the problem here which i am having in my own project where i am trying to implement this intersection test between line and polygonal shape. If you uncomment it and then comment the next one instead , everything works just fine. This is where i think is the problem. My question is how do i get rid of this in my projeject?


Let me know how it went along at your side.


Regards
Sajjad

[wysota]

The problem is I don't know what you modified in those files and comparing them by hand is tedious enough that it prevents me from doing it and comparing them automatically is not possible since you changed formatting of those files.

[sajis997]

I assume the fact that it did not go well at your side. So please go to the following website and download the .zip file named diagramsceneupdated3.zip

http://www.student.itn.liu.se/~sajis...neupdated3.zip

I hope that file formating issue will not arise anymore and you will be able to edit.

If you manage to run it, please try to add elliptical items and connect them with a arrow and try to move around the scene and you will see the problem.

Let me know if any other issues show up and thank you again for your effort to solve the issue.


Regards
Sajjad

[wysota]

Let's make it clear -- I am able to run it and I can see the malfunction, the problem is that not knowing what you have changed makes it hard to find the problem. That's why we ask about a minimal compilable example reproducing the problem, not an edited example reproducing the problem Create a simple program with two elipses and a line connected to them that reproduces the problem (up to 50 lines of code in total).