Problem in attachig two polygons

[rohitjun]

Hi,
I am doing one application in which, i wrote one class A to create different shapes of polygons. Then i wrote another class B for creating a special polygon which i have to attach with polygons of class A dynamically. Before i did somethinig similar but with QGraphicsItem class using setPos() function for attaching one polygon with another. But with QPolygon, it is working similar. Please suggest me some way.

Regards
Rohit

This is the constructor of class A

A::A(DiagramType diagramType, QMenu *contextMenu,
             QGraphicsItem *parent, QGraphicsScene *scene)
    : QGraphicsPolygonItem(parent, scene)
{
    myDiagramType = diagramType;
    myContextMenu = contextMenu;
 
    QPainterPath path;
 
    switch (myDiagramType) {
 
        case StartEnd:
            path.moveTo(200, 50);
            path.arcTo(150, 0, 50, 50, 0, 90);
            path.arcTo(50, 0, 50, 50, 90, 90);
            path.arcTo(50, 50, 50, 50, 180, 90);
            path.arcTo(150, 50, 50, 50, 270, 90);
            path.lineTo(200, 25);
            myPolygon = path.toFillPolygon();    //myPolygon is an object QPolygonF class
            break;
 
        case Conditional:
            myPolygon << QPointF(-100, 0) << QPointF(0, 100)   
                      << QPointF(100, 0) << QPointF(0, -100)
                      << QPointF(-100, 0);
            break;
 
       case Step:
            myPolygon << QPointF(-100, -100) << QPointF(100, -100)
                      << QPointF(100, 100) << QPointF(-100, 100)
                      << QPointF(-100, -100);
 
           break;
 
        default:
            myPolygon << QPointF(-120, -80) << QPointF(-70, 80)
                      << QPointF(120, 80) << QPointF(70, -80)
                      << QPointF(-120, -80);
            break;
    }
 
    anditem = new AndItem();
 
///// What code to write to attach andItem->myPolygon to myPolygon of this class.////
 
 
    setPolygon(myPolygon);
    setFlag(QGraphicsItem::ItemIsMovable, true);
    setFlag(QGraphicsItem::ItemIsSelectable, true);
 
}

A::A(DiagramType diagramType, QMenu *contextMenu,
             QGraphicsItem *parent, QGraphicsScene *scene)
    : QGraphicsPolygonItem(parent, scene)
{
    myDiagramType = diagramType;
    myContextMenu = contextMenu;

    QPainterPath path;

    switch (myDiagramType) {

        case StartEnd:
            path.moveTo(200, 50);
            path.arcTo(150, 0, 50, 50, 0, 90);
            path.arcTo(50, 0, 50, 50, 90, 90);
            path.arcTo(50, 50, 50, 50, 180, 90);
            path.arcTo(150, 50, 50, 50, 270, 90);
            path.lineTo(200, 25);
            myPolygon = path.toFillPolygon();    //myPolygon is an object QPolygonF class
            break;

        case Conditional:
            myPolygon << QPointF(-100, 0) << QPointF(0, 100)   
                      << QPointF(100, 0) << QPointF(0, -100)
                      << QPointF(-100, 0);
            break;

       case Step:
            myPolygon << QPointF(-100, -100) << QPointF(100, -100)
                      << QPointF(100, 100) << QPointF(-100, 100)
                      << QPointF(-100, -100);

           break;

        default:
            myPolygon << QPointF(-120, -80) << QPointF(-70, 80)
                      << QPointF(120, 80) << QPointF(70, -80)
                      << QPointF(-120, -80);
            break;
    }

    anditem = new AndItem();

///// What code to write to attach andItem->myPolygon to myPolygon of this class.////


    setPolygon(myPolygon);
    setFlag(QGraphicsItem::ItemIsMovable, true);
    setFlag(QGraphicsItem::ItemIsSelectable, true);

}

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[marcel]

Take the painter path of the first polygon (a QPainterPath ) and use QPainterPath::addPath to add your second polygon ( which I assume is also a QPainterPath ).

Next, set the shape back to the first item. This is what I understand by "attached".
I don't know how convenient is this for you.
Maybe you don't want to modify the geometry of your items.

Regards

[rohitjun]

Thanks Marcel...

Now i try what you suggested but before just to tell u what i want as output. An example jpg is attached with two polygons.

Reg
Rohit

[marcel]

In this case you should try another approach.

1. Take the bounding box of the first polygon.
2. Take the bounding box of the second polygon
3. Move the second polygon such that is left bbox coordinate is equal to the right bbox coordinate of the first polygon.

Keep in mind that you may not get acceptable results for complex polygons.

[rohitjun]

Dear Marcel......

I added these lines in the same constructor of class A, because of the first two points you mentioned in the last post.


myGateRect= myPolygon.boundingRect();// QRectF myGaterect;
anditem = new AndItem();
myPolygonConnector =anditem->polygon(); // QPolygonF myPolygonConnector;
myConnectorRect= myPolygonConnector.boundingRect();//QRectF myConnectorRect;

I am not able to proceed aftre this.
Please help..
Rohit

[marcel]

Next you have to bring the items next to each other by using either moveBy or setPos, whatever suites you.

[rohitjun]

Marcel

Does "setPos" or "MoveBy" works with QPolygon object. Sorry if i ask some silly question. Because it is not working for me.

Rohit

[marcel]

No, I meant QGraphicsItem::setPos or QGraphicsItem::moveBy.
You should work directly with the graphics items, and not the shapes themselves. Perhaps create a group out of A and B?

Regards

[rohitjun]

Dear Marcel

Yes Marcel, I was trying to use setPos with polygon :-) I am silly.... But these classes are derived from of QGraphicsItem. So now setPos is fine...But my problem is not solved because
....
I dont have the screen coordinates so that i can move them or set their position because the QPolygonF item is placed on the screen at run time. This is handled in the mouse press events of the screen window class. So when at run time object is created, it should have these polygon connected (As forexample gate with connector).

If its ok for you then i send my code.

Rohit

[marcel]

Sure, it is better to post the code.

Regards

[rohitjun]

Dear Marcel
Now i am at home....:-)
I tried to attach complete code but it is big. So i am attaching five files. "This code is similar to the example in QT4.3 examples but a little difference"
Explanation :- The application has buttons on the left when the user click any button and then click in the screen window the polygon is pasted there whose picture was displayed on the button clicked. But i want that polygons in DiagramItems works as different gates and i can add any number of connectors at run time to that. But standard are one input and two output connectors(polygon) with a gate(Polygon).
So i created a class "Gate.cpp" (Attached) which contains AndItem class which creates a polygon works as connector to gate and i tried to create a run time object of AndItem class mentioned in "Gate.cpp" file in the constructor of the DiagramItem class which creates diffrent types. Now if the user click the button and then click the screen window there are two polygon pasted which will together as Gate polygon and connector polygon. Then i will modify for connecting two polygons with arrow.
I am new to Qt and any help ,i will take it gladly.
Thanks for your guidance Marcel.
Sorry if i give you any trouble.
Rohit

[marcel]

Hello,

I assume you are trying to make some kind of electronic circuits designer.
I'm afraid that your approach is a little too simple.

You should keep account of your ports.
For example, let's say you have an AND port in the scene.
Next, you add an OR port and you want to connect it to the output of the AND port.
Initially the OR port will be placed somewhere in the scene. You drag it with the mouse and when you are near the output of the and the OR will snap to the AND port and automatically a connector will be created.

By snap I mean that one input of the OR port will be aligned to the output of the AND gate.
If you drag it further the connector disappears.

All I am trying to say is that your app should be more interactive.

Keeping account of the items is not hard. You always can access them via QGraphicsScene::items.

When you drag a port you just look at the other items near it, to see if you can connect to one of the them ( maybe define a snap distance ).

Regards

[rohitjun]

Thanks alot for such a precious reply Marcel

You are perfectly right that i am trying ot build a electronic desing application.

yes i completely agree with you that my application should be more interactive.

But the ports will not be attached automatically when they come near to each other.The user has to click one of the connector output of the "suppose" OR port and the drag the mouse till the inut connector of "suppose" And port. Then the connection between the two ports will be established.

I thought of a approach, " When the user put a port on the scene then it will have one input and two output connector. But if the user wish to add or delete any connector he has to right click and then add or delete the connector through pop up menu. So in the begining i am trying to create a Port with connectors which user can put on the scene window. Connector polygon will handle the wiring between ports."

Please give some suggestions on it.
If you think , i am wrong way, please tell any other approach.

Regards
Rohit

[rohitjun]

Dear Marcel

Good morning

I tried to make two polygons join together. But setPos,moveBy doesnt work for me as well as i tried to combine directly when i use setPolygon(First polygon+ second polygon) function but this create one polygon over another.
Now i am thinking of not to use connector class. I think i can set some points on the Port(AND) itself which can be used to connect to other ports. It means any port will connect to new port with a new point for wiring whenever the user will wire to a new port.

Please suggest,

Rohit