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Thread: Having problems with transformations

  1. #1
    Join Date
    May 2007
    Lublin, Poland
    Thanked 8 Times in 4 Posts
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    Default Having problems with transformations

    Hi guys,

    I have implemented my own QGraphicsScene::drawBackground(QPainter* ....) method.
    I draw a map in that method, but before drawing, to get the correct image, I had to make these transformations:
    Qt Code:
    1. ....
    2. painter->translate(550,300);
    3. painter->rotate(180);
    4. painter->scale(-3.37778,3.37778);
    6. painter->drawRect(m_rectangle);
    7. ...
    To copy to clipboard, switch view to plain text mode 
    and then I got the correct map drawn. In this method I also draw same rectangles.

    Now, after I have my map and the rectangles drawn in the drawBackground(QPainter*..) I need to add some QGraphicsTextItems in the center of that rectangles, but I have problems with finding the transformation for the items to draw them in the correct place.
    Now I need to add a QGraphicsTextItem in the center of the "m_rectangle";

    I tried using the same transform (*****) for my items (like item->translate()...etc), but they I drawn in the wrong place.

    How can I get the QGraphicTexItem added in the center of the m_rectangle(which is drawn in the drawBackground(QPainter*) ) ??

    I do appreciate any ideas.
    Thank you

    Qt allows you to use everything you want
    #if defined(Q_OS_UNIX) && defined(QT_DEBUG)
    abort(); // trap; generates core dump
    exit(1); // goodbye cruel world

  2. #2
    Join Date
    Jan 2006
    Warsaw, Poland
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    Default Re: Having problems with transformations

    You can map rectangle between different matrices using QMatrix::map(). It's just a matter of picking the right pair of matrices.

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