Qt: Force QGraphicsItem to update

Question

According to Qt Documentation, " void QGraphicsItem::update ( const QRectF & rect = QRectF() ) " does not cause an immediate paint; instead it schedules a paint request that is processed by QGraphicsView after control reaches the event loop. Here is my code:

this->item->setPixmap( QPixmap::fromImage(*coloration->image) );// QGraphicsPixmapItem 
this->item->update();
this->scene->update(); // QGraphicsScene
this->view->update(); // QGraphicsView

and the code is in a method that will be invoked every 100 milliseconds(and in which the coloration->image will change), but the Qt refuses to update the image every 100 milliseconds, and it only renders the final image. So, how could I paint the item immediately?

@graphite Actually, my project doesn't produce animation, it just do some processing of an image and then updates the image, so I think animation is not an appropriate option. Do you have any idea how to deal with problem by using QGraphicsItem? — JavaBeta
@graphite Thanks for your reply! I found that repainting the viewport will do the job! So in the method, just call this->item->setPixmap( QPixmap::fromImage(*coloration->image) ); this->view->viewport()->repaint(); — JavaBeta
@JavaBeta thanks a lot spend so much time one that. And it was viewport. I think you should write this as a answer . And accept it yourself for readers. — Kadir Erdem Demir

Kuba hasn't forgotten Monica Kuba hasn't forgotten Monica · Accepted Answer · 2013-11-11T22:30:36

You must be blocking your event loop, or your implementation of the item is otherwise bad. I can't reproduce your issue.

Qt: Force QGraphicsItem to update

2 Answers