Change in the geometry of item on changing parent

djasmine

Say I have an item A which is child of a parent P1.
Now I rotate item A by 180.
I have another item P2 which is rotated by 90 and horizontally mirrored.
Now when I try to make P2 as parent of item A, it's position, rotation and mirroring gets completely modified.

I am able to fix the position of item by adjusting it based on its scene position.
But I am unable to get its original transformations (rotate/mirror) back.
How can I resolve this??
Also is there any way to modify the scene transformation of any item ??

SGaist

Hi,

Can you share the related code ?

djasmine

/* Below I am sharing a minimal stand alone code simulating the problem shared above, its not the actual code from my project */

QGraphicsView graphicsView;
QGraphicsScene *scene = new QGraphicsScene(&graphicsView);
graphicsView.setScene(scene);

QGraphicsRectItem * parent1 = new QGraphicsRectItem();
parent1 ->setRect(QRectF(-100, -50, 200, 100);
parent1->setPos(100, 100);
scene->addItem(parent1 );

QGraphicsRectItem * parent2 = new QGraphicsRectItem();
parent2 ->setRect(QRectF(-100, -50, 200, 100);
parent2->setPos(250, 250);
scene->addItem(parent2 );

//parent1 being set as parent of text
QGraphicsSimpleTextItem * text = new QGraphicsSimpleTextItem();
text->setText("I am Text");
text->setParentItem(parent1);
text->setPos(QPointF(0,0));

//rotate parent2 by 90 and then make it as parent of text
QTransform tr;
tr.rotate(90);
parent2->setTransform(tr);
text->setParentItem(parent2);

Now text will jump to another position along with some rotation applied (inherited from parent).
I am to handle to jump in position as below:

QPointF oldPos = text->mapToScene(pos()); //fetch scene pos before setting parent2
QPointF newPos = text->maptoScene(pos()); // fetch pos after setting parent2

text->setPos( pos() + (oldPos - newPos) );

Now text stays where it was created but rotates.
How to stop rotation?
I know there is a flag itemIgnoresTransformation.
In our case there is a hierarchy of parents and some view transformations like zoom which we want to get automatically passed on to all the child items.
So itemIgnoresTransformation is not the solution.

djasmine

Anybody having any expertise around this problem, please share.

SGaist

From the looks of it, you would have to implement your own filtering of the transformations applied to your scene but since it's all handled on a lower level.

See the QGraphicsSceneBspTreeIndex.