Drawing the background of QGraphicsView

[aknuds1]

I did try resetCachedContent(), but it did nothing really. Besides, caching is turned off by default according to Assistant.

[maxpower]

My GV is created in a UI file and then as part of my program's init i set a brackground. This is the code I use:

QString fieldImage = ":/images/Field.png";
        scene = new QGraphicsScene();
        scene->setSceneRect(0, 0, fieldWidth, fieldHeight);
        fieldGV->setRenderHints(QPainter::Antialiasing | QPainter::SmoothPixmapTransform);
        fieldGV->setBackgroundBrush(QImage(fieldImage));
        fieldGV->setCacheMode(QGraphicsView::CacheNone);
        fieldGV->setScene(scene);

QString fieldImage = ":/images/Field.png";
        scene = new QGraphicsScene();
        scene->setSceneRect(0, 0, fieldWidth, fieldHeight);
        fieldGV->setRenderHints(QPainter::Antialiasing | QPainter::SmoothPixmapTransform);
        fieldGV->setBackgroundBrush(QImage(fieldImage));
        fieldGV->setCacheMode(QGraphicsView::CacheNone);
        fieldGV->setScene(scene);

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Hope it helps.

mAx

[aknuds1]

My GV is created in a UI file and then as part of my program's init i set a brackground. This is the code I use:

QString fieldImage = ":/images/Field.png";
        scene = new QGraphicsScene();
        scene->setSceneRect(0, 0, fieldWidth, fieldHeight);
        fieldGV->setRenderHints(QPainter::Antialiasing | QPainter::SmoothPixmapTransform);
        fieldGV->setBackgroundBrush(QImage(fieldImage));
        fieldGV->setCacheMode(QGraphicsView::CacheNone);
        fieldGV->setScene(scene);

QString fieldImage = ":/images/Field.png";
        scene = new QGraphicsScene();
        scene->setSceneRect(0, 0, fieldWidth, fieldHeight);
        fieldGV->setRenderHints(QPainter::Antialiasing | QPainter::SmoothPixmapTransform);
        fieldGV->setBackgroundBrush(QImage(fieldImage));
        fieldGV->setCacheMode(QGraphicsView::CacheNone);
        fieldGV->setScene(scene);

To copy to clipboard, switch view to plain text mode 

Hope it helps.

mAx

Thanks for the tip, but the problem is rather that I want to trigger redrawing of the background at some point. Initial drawing of the background is no problem.

[aamer4yu]

do the image width and height and Scene rect width/height match ??

might be thers some scaling problem ???

[maxpower]

Okay, but why can't you use setBackGroundBrush() again? I can call that from anywhere in my app and the background changes just fine. I guess it depends on exactly what you are trying to draw as the background.

mAx

[rajesh]

workaround.
just add one item to scene and remove, this will redraw the background.

[Bitto]

Or define the scene rect, no workaround needed. ;-)

[giverson]

is it a partial background refresh where it just refreshes the scene and leaves everything outside the scene the old background color or does it just plain not work?

You might also try updating to 4.2.3 since it looks like they did something on this...

"General improvements
--------------------

- Graphics View

* Calling QGraphicsScene::update() without arguments now correctly
updates the entire scene.
* Changing the background brush in QGraphicsScene now correctly updates
the entire scene
"

[camel]

I did try resetCachedContent(), but it did nothing really.

Could you post a little programm (i.e. minimal but runable ;-) That shows the behaviour? That makes helping easier :-)

[aknuds1]

Could you post a little programm (i.e. minimal but runable ;-) That shows the behaviour? That makes helping easier :-)

I'll see what I can do tomorrow.