[PyKDE] QCanvas items: self created ClassItem appears as QCanvasPolygon or similar

Phil Thompson phil at riverbankcomputing.co.uk
Sun May 30 14:13:01 BST 2004

On Sunday 30 May 2004 12:43 pm, Karl wrote:
> Hi!
> Approx. 2 years ago, me and some collegues created a program in university
> using Python and Qt 2. It worked then, now I want to try to port it to Qt 3
> and then finish/improve it.
> I found some very strange behaviour and would ask, whether anyone knows
> what is wrong?
> Problem description:
> I have a Canvas, on this Canvas, I put some Items.
> To do this, I created a class that is called "ClassItem" (the program is a
> case tool, ClassItem represents a class) that inherits QCanvasRectangle and
> a Class called Item that has some logical stuff about my items.
> This is a short excerpt from the constructor of ClassItem:
>  >class ClassItem (QCanvasRectangle, Item):
>  >	def __init__(self, guiManager, clsId):
>  >		Item.__init__(self, guiManager, CLASSTYPE, clsId, 1)
>  >		QCanvasRectangle.__init__(self, self.canvas)
> Now, when I create my ClassItems, they should be added to the Canvas just
> when the constructor calls QCanvasRectangle.__init__(...), right?
> But somehow, not all these Items are added to the canvas as *ClassItem*,
> but e.g. as QCanvasPolygon.
> Excerpt from my debug output:
>  >.adding class
>  >..class created: <ClassItem.ClassItem object at 0x00912FC0>
>  >..items now on Canvas: [<ClassItem.ClassItem object at 0x00912FC0>]
>  >.adding class
>  >..class created: <ClassItem.ClassItem object at 0x00917030>
>  >..items now on Canvas: [<ClassItem.ClassItem object at 0x00917030>,
> <ClassItem.ClassItem object at 0x00912FC0>]
>  >.adding class
>  >..class created: <ClassItem.ClassItem object at 0x009170C0>
>  >..items now on Canvas: [<ClassItem.ClassItem object at 0x00917030>,
> <__main__.qtcanvas.QCanvasPolygon object at 0x009170F0>,
> <ClassItem.ClassItem object at 0x00912FC0>]
> As you can see, the third ClassItem is in fact created as ClassItem, but it
> is added to the Canvas as QCanvasPolygon.
> I don't see any difference between these items and don't understand, why
> the program behaves this way...
> In the following, the QCanvas.collisions()-method results this
> QCanvasPolygon, on which I cannot call the methods, that are specific for
> ClassItem, therefore, there is no difference for me, if this ClassItem is
> present or not, I cannot work with it...
> Can anyone help, please?

Can you put together a small, but complete, script that demonstrates the 

What versions of SIP, PyQt and Qt are you using?


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