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Implementing the QGraphicsView Zoom Slider

I need to integrate the zoom slider for QGraphicsViewin Qt 4.x, I have a working implementation that looks something like this:

connect(slider, SIGNAL(valueChanged(int)), customGraphicsView, SLOT(setZoomLevel(int));

In the slot for setZoomLevelI have the following

void CustomView::setZoomLevel(int level)
{
    if(zoomLevel - level < -1){
        setZoomLevel(level - 1);
    }else if(level - zoomLevel < -1){
        setZoomLevel(level + 1);
    }
    if(level < zoomLevel){
        scale(1 - (scaleFactor * (zoomLevel - level)), 1 - (scaleFactor * (zoomLevel - level)));
    }else if (level > zoomLevel){
        scale(1 + (scaleFactor * (level -  zoomLevel)), 1 + (scaleFactor * (level -  zoomLevel)));
    }

    zoomLevel = level;
}

So my problem is conjugating a slider that has a value from n to m to represent the zoom level for a function scale() QGraphicsViewthat takes two floating point values ​​to propagate the scene to get a new size.

So the problem I am facing is that if you accept 1 * .9 * 1.1, you still will not get 1, but instead .99, this is a bit because this is not the right formula. Thus, my maximum increase becomes less and less over time.

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+5
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setTransform(QTransform::fromScale(sx, sy));

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+7

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