QGraphicsItem not repainting

[eijnuhs]

Hello,

I am trying to reimplement the colliding mouse example.
Everything is the same except
QMainWindow is used.
I used the timer event to set new random position on the scene.
So far so good, I can see my QGraphicsItem on the scene.
However, the problem is that is not moving..and sometimes parts of the item on the scene will start disappearing. And I can actually 'see the item moving' or moved to a new location if I keep resizing my window or I have a scene->update() command.

Anybody has any idea why ?

Thanks !

[aamer4yu]

Hard to say without seeing code

Also u say u are using QMainwindow,,, have u set central widget properly ? and parents of scene and items ? or may be some problem with timer ?

[eijnuhs]

Update to what I did..

I added

scene()->update()

scene()->update()

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in my QGraphicsItem subclass's timer event method when the item updates its position.
It solves my repainting issue but felt its a crude way, and I will look for other means to do it.

On a side note,

Does anyone know how QGraphicsScene::changed(const QList (QRectf) rect) signal works ?
What is meant by emits signal scene's content changes ? Does that include position of the QGraphicsItem ?

How is it used most commonly ?

Ask quite abit this time but I will keep you guys updated with whatever I find.

And same as before, Thanks for reading !

[patrik08]

Update to what I did..
I added

scene()->update()

scene()->update()

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in my QGraphicsItem subclass's timer event method when the item updates its position.
It solves my repainting issue but felt its a crude way, and I will look for other means to do it.
On a side note,
Does anyone know how QGraphicsScene::changed(const QList (QRectf) rect) signal works ?
!

i reload scene by item on this way:

i need only by move elemenst or rotate , resize (paint outside from rect() item)

/* item */
void TextLayer::sceneReload()
{
     GraphicsScene *sc;
     if (sc = qobject_cast<GraphicsScene *>(scene())) {
     sc->clearSelection();
     }
}
/* scene */
void GraphicsScene::clearSelection()
{
    QGraphicsScene::clearSelection();
    /* actual rect sceneRect() or view port */
    update(sceneRect());
}

/* item */
void TextLayer::sceneReload()
{
     GraphicsScene *sc;
     if (sc = qobject_cast<GraphicsScene *>(scene())) {
     sc->clearSelection();
     }
}
/* scene */
void GraphicsScene::clearSelection()
{
    QGraphicsScene::clearSelection();
    /* actual rect sceneRect() or view port */
    update(sceneRect());
}

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or i send a setVisibleArea( const QRectF area ) to scene

void GraphicsScene::setVisibleArea( const QRectF area )
{
    emit MakeVisible(area);  /* to GraphicsView */
}
 
void GraphicsView::viewDisplay( const QRectF area )
{
 
    /* if scale to big return text no readable  */
    QMatrix matx = matrix();
    qreal HHscaled = matx.m11();
    if (HHscaled > 5.1) {
    return;
    }
    QGraphicsView::ensureVisible(area);
}

void GraphicsScene::setVisibleArea( const QRectF area )
{
    emit MakeVisible(area);  /* to GraphicsView */
}

void GraphicsView::viewDisplay( const QRectF area )
{
    
    /* if scale to big return text no readable  */
    QMatrix matx = matrix();
    qreal HHscaled = matx.m11();
    if (HHscaled > 5.1) {
    return;
    }
    QGraphicsView::ensureVisible(area);
}

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