Hud and QGraphicsView

andre

Doesn't the QGraphicsItem::ItemIgnoresTransformations flag provide that functionality?

Andrea Mugnaini

If i add a qwidget on top of qgraphicsview, i note some problems with alpha channel of widget's background.

furthermore

if i set the flag of QGraphicsProxyWidget (got after calling addWidget on qgraphicscene) with ItemIgnoresTransformations, nothing happens.
...
A Solution could be: fix the qgraphicsview on qgraphicsscene, then scroll manually the content of qgraphicscene.

Andrea Mugnaini

Strange,
if i setViewport with QWidget instead QGLWidget, it works (I can see a correct blending between the transparencies of the backgrounds).
...

Hence, recapping:

I have a QWidget (my hud) with transparent background;
My hud is a son of QGraphicsView;
If the QGraphicsView has a viewport of type QWidget, i can see correct blending of backgrounds.
If the QGraphicsView has a viewport of type QGLWidget, i see a black background for my Hud.

Comments?

Many Thanks.

deimos

for transparencies in openGL I think you can try this:
@qgl=new QGLWidget(new QGLContext(QGLFormat(QGL::Rgba | QGL::DoubleBuffer | QGL::AlphaChannel | QGL::HasOverlay)));
setViewport(qgl);@

and to retrieve the coordinates to draw your HUD sticky to a position, you have to calculate the mapped position relatively to the current scene. For example, if you want to draw it at coords (10,10) of QGraphicsView widget:
@pos=mapToScene(10,10);
hud.setPos(pos);@

hope this help

Andrea Mugnaini

First of all, thanks for the support.

I tried the suggestion above but, nothing happens.
Hence, i invite you to see with your eyes the problem,
you can download this:
"TestHudView":https://sites.google.com/site/mugnaini81/TestHudView.zip?attredirects=0&d=1

you can try to uncomment(or hack) inside @void ZGraphicsView::Init()@

Many thanks.

deimos

I didn't know why a transparent widget over a openGL GraphicsView isn't transparent. I think some function like initGL and updateGL should be reimplemented correctly, but you can reimplement "QGraphicsView::drawForeground":http://doc.qt.nokia.com/latest/qgraphicsview.html#drawForeground to positioning the "QGraphicsProxyWidget *hud" when needed as follow

@void ZGraphicsView::drawForeground ( QPainter * painter, const QRectF & rect )
{
hud->setPos(mapToScene(100, 10));
}

void ZGraphicsView::Init()
{
//------------------- CHECK THIS! -------------------
// setViewport(new QWidget());
setViewport(new QGLWidget(new QGLContext(QGLFormat(QGL::Rgba | QGL::DoubleBuffer | QGL::AlphaChannel | QGL::HasOverlay))));
//---------------------------------------------------

// Hud Settings (on QGraphicsView)
QLabel* label = new QLabel("HUD!", 0);
label->setStyleSheet("QLabel{background: transparent; color: red; font: 40px;}");
label->setFixedSize(100, 44);
label->move(0, 0);

// Background settings (on QGraphicsScene)
ZGraphicsScene* scene = new ZGraphicsScene();
QGraphicsPixmapItem* myBackground = new QGraphicsPixmapItem(QPixmap(":/background.png"), 0);
scene->addItem(myBackground);
setScene(scene);
setFixedSize(myBackground->boundingRect().size().toSize());

hud = scene->addWidget(label);
hud->setPos(mapToScene(100, 10));

show();

}@

Andrea Mugnaini

[quote author="MarcoB" date="1297775701"] but you can reimplement "QGraphicsView::drawForeground":http://doc.qt.nokia.com/latest/qgraphicsview.html#drawForeground to positioning the "QGraphicsProxyWidget *hud" when needed as follow
[/quote]

The Test that i added above it isn't my true case.
In my case, i can't do it, because (for now) i have the QGraphicsView that scrolls a QGraphicsScene, so if i move my hud to fixed position, whenever drawForeground is executed, i see that my hud flickers with scrolling.

Many Thanks.

saddan

Hi,

Did you solve the transparency problem with widgets added to the scene?

Andrea Mugnaini

Yes, i solved this problem (more or less).
You can find my game here:
http://sites.google.com/site/mugnaini81/Psycho-naut_source_code_v016.zip

but, now i am using another kind of solution for the hud cause i stopped to use the qgraphicsview system.

Basically I am developing a 3D shoot' em up, using a QGLWidget with an hybrid system for the hud: ortographic projection+qfont+opengl commands.

Alain38

As I found this topic searching another similar problem, just a way to have a transparent widget on an OpenGL background:
@widget->setWindowOpacity(0.95);
widget->setAttribute(Qt::WA_TranslucentBackground);@

The opacity value is just to see what you put in the widget. The only forbidden value is 1.0.