How to Transparent QGraphicsView widget Background?

[ashukla]

Dear Everyone!
How to Transparent QGraphicsView widget background?

[jpn]

What did you try so far?

graphicsView->setStyleSheet("background: transparent");

graphicsView->setStyleSheet("background: transparent");

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[ashukla]

What did you try so far?

graphicsView->setStyleSheet("background: transparent");

graphicsView->setStyleSheet("background: transparent");

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I have tried this one earlier as you suggested.But It sets the Background WHITE not a Tranparent.

[jpn]

Works for me with Qt 4.3.2.

[ashukla]

Works for me with Qt 4.3.2.

Dear Sir!

I am using the following code in Qt 4.3.2.

QGraphicsTextItem *scrItem = new QGraphicsTextItem(scrText);
	scrItem->setDefaultTextColor(QColor(Qt::red));
 
	QGraphicsScene *scene=new QGraphicsScene();
 
	QGraphicsItemAnimation *animation = new QGraphicsItemAnimation;
 	QGraphicsItemAnimation *animation1 = new QGraphicsItemAnimation;
    animation->setItem(scrItem);
    float n;
	screen=QApplication::desktop()->screenGeometry();
	int yLoc=screen.height()-(scrFont.pointSize()+40);
	wScroller->setGeometry(0,yLoc,wScroller->width(),scrFont.pointSize()+40);
	view=new QGraphicsView(scene,wScroller);
	view->setWindowFlags (Qt::FramelessWindowHint);
	view->setStyleSheet("background: transparent"); 
	scene->addItem(ship);
	scene->addItem(scrItem);
 
	view->setVerticalScrollBarPolicy( Qt::ScrollBarAlwaysOff );
	view->setHorizontalScrollBarPolicy( Qt::ScrollBarAlwaysOff );
	view->setCacheMode(QGraphicsView::CacheBackground);
 
	scene->setSceneRect(0,0,wScroller->width(),scrFont.pointSize()+40);
	n=scrWidth;/*Width of  scrText*/
 
	qreal sh=scene->height()/2-ship->boundingRect().height()/2;
	qreal h=scene->height()/2-scrItem->boundingRect().height()/2;	/*Calculating the eaxact mid Y cordinate position of scrItem (Text)*/
 
 
	register int scrItembrw=scrItem->boundingRect().width();
	register int velNum=16;
    register int velocity=(((velNum-scrSpeed)*3)-2);
	register int tl=(n+scrItembrw)*velocity;
	scrTime=tl;
 
	timer = new QTimeLine(tl);
	timer->setCurveShape(QTimeLine::LinearCurve);
	timer->setLoopCount(0);
	animation->setTimeLine(timer);
	animation1->setTimeLine(timer);
 
 
	for (int i=0; i<(n+scrItem->boundingRect().width()); i=i+1)
	{
		QPointF p(0,h);
		p.setX(n-i);
		p.setY(h);
		ps.setX(n-i-imgbrw);
		ps.setY(sh);
		animation->setPosAt(i/(n+scrItem->boundingRect().width()),p);
 
	 }//end for
 
	view->setFixedWidth(wScroller->width());
	view->setFixedHeight(scene->height());
	view->show();
	timer->start();

QGraphicsTextItem *scrItem = new QGraphicsTextItem(scrText);
	scrItem->setDefaultTextColor(QColor(Qt::red));

	QGraphicsScene *scene=new QGraphicsScene();
	
	QGraphicsItemAnimation *animation = new QGraphicsItemAnimation;
 	QGraphicsItemAnimation *animation1 = new QGraphicsItemAnimation;
    animation->setItem(scrItem);
    float n;
	screen=QApplication::desktop()->screenGeometry();
	int yLoc=screen.height()-(scrFont.pointSize()+40);
	wScroller->setGeometry(0,yLoc,wScroller->width(),scrFont.pointSize()+40);
	view=new QGraphicsView(scene,wScroller);
	view->setWindowFlags (Qt::FramelessWindowHint);
	view->setStyleSheet("background: transparent"); 
	scene->addItem(ship);
	scene->addItem(scrItem);
	
	view->setVerticalScrollBarPolicy( Qt::ScrollBarAlwaysOff );
	view->setHorizontalScrollBarPolicy( Qt::ScrollBarAlwaysOff );
	view->setCacheMode(QGraphicsView::CacheBackground);
	
	scene->setSceneRect(0,0,wScroller->width(),scrFont.pointSize()+40);
	n=scrWidth;/*Width of  scrText*/
	
	qreal sh=scene->height()/2-ship->boundingRect().height()/2;
	qreal h=scene->height()/2-scrItem->boundingRect().height()/2;	/*Calculating the eaxact mid Y cordinate position of scrItem (Text)*/
	
	
	register int scrItembrw=scrItem->boundingRect().width();
	register int velNum=16;
    register int velocity=(((velNum-scrSpeed)*3)-2);
	register int tl=(n+scrItembrw)*velocity;
	scrTime=tl;
    	
	timer = new QTimeLine(tl);
	timer->setCurveShape(QTimeLine::LinearCurve);
	timer->setLoopCount(0);
	animation->setTimeLine(timer);
	animation1->setTimeLine(timer);
	
	
	for (int i=0; i<(n+scrItem->boundingRect().width()); i=i+1)
	{
		QPointF p(0,h);
		p.setX(n-i);
		p.setY(h);
		ps.setX(n-i-imgbrw);
		ps.setY(sh);
		animation->setPosAt(i/(n+scrItem->boundingRect().width()),p);
   		
	 }//end for
	
	view->setFixedWidth(wScroller->width());
	view->setFixedHeight(scene->height());
	view->show();
	timer->start();

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but it is not working.

[jpn]

Give the following example a try:

#include <QtGui>
 
int main(int argc, char *argv[])
{
    QApplication app(argc, argv);
    QMainWindow window;
 
    QGraphicsScene* scene = new QGraphicsScene(&window);
    QGraphicsItem* item = scene->addText("QGraphicsTextItem");
    item->setFlags(QGraphicsItem::ItemIsMovable);
 
    QGraphicsView* view = new QGraphicsView(&window);
    view->setStyleSheet("background: transparent");
    view->setScene(scene);
 
    window.setCentralWidget(view);
    window.setStyleSheet("background: green");
    window.show();
    return app.exec();
}

#include <QtGui>

int main(int argc, char *argv[])
{
    QApplication app(argc, argv);
    QMainWindow window;
    
    QGraphicsScene* scene = new QGraphicsScene(&window);
    QGraphicsItem* item = scene->addText("QGraphicsTextItem");
    item->setFlags(QGraphicsItem::ItemIsMovable);
    
    QGraphicsView* view = new QGraphicsView(&window);
    view->setStyleSheet("background: transparent");
    view->setScene(scene);

    window.setCentralWidget(view);
    window.setStyleSheet("background: green");
    window.show();
    return app.exec();
}

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As you can see, the background of the main window shows through the view.

view=new QGraphicsView(scene,wScroller);
view->setWindowFlags (Qt::FramelessWindowHint);

view=new QGraphicsView(scene,wScroller);
view->setWindowFlags (Qt::FramelessWindowHint);

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What are you trying to accomplish with this? You pass a parent so it's not a top level widget you could remove window frames from. If you actually want to adjust transparency of a top level widget, take a look at QWidget::setWindowOpacity() but make sure you read the notes in docs.

[ashukla]

Give the following example a try:

#include <QtGui>
 
int main(int argc, char *argv[])
{
    QApplication app(argc, argv);
    QMainWindow window;
 
    QGraphicsScene* scene = new QGraphicsScene(&window);
    QGraphicsItem* item = scene->addText("QGraphicsTextItem");
    item->setFlags(QGraphicsItem::ItemIsMovable);
 
    QGraphicsView* view = new QGraphicsView(&window);
    view->setStyleSheet("background: transparent");
    view->setScene(scene);
 
    window.setCentralWidget(view);
    window.setStyleSheet("background: green");
    window.show();
    return app.exec();
}

#include <QtGui>

int main(int argc, char *argv[])
{
    QApplication app(argc, argv);
    QMainWindow window;
    
    QGraphicsScene* scene = new QGraphicsScene(&window);
    QGraphicsItem* item = scene->addText("QGraphicsTextItem");
    item->setFlags(QGraphicsItem::ItemIsMovable);
    
    QGraphicsView* view = new QGraphicsView(&window);
    view->setStyleSheet("background: transparent");
    view->setScene(scene);

    window.setCentralWidget(view);
    window.setStyleSheet("background: green");
    window.show();
    return app.exec();
}

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As you can see, the background of the main window shows through the view.


What are you trying to accomplish with this? You pass a parent so it's not a top level widget you could remove window frames from. If you actually want to adjust transparency of a top level widget, take a look at QWidget::setWindowOpacity() but make sure you read the notes in docs.

Dear Sir!
Actually, I have designed three QX11EmbedContainer widget (as a child namely f1,f2,f3 dynamically) of QX11Container parent widget. I am playing in f1 & f2 frames different movies and in the third f3 child widget I want to play scrolling text like news with transparent background.
for which I am using the above code.

QScrollerViewPlayer::QScrollerViewPlayer(QString file, int width, int height, QWidget *wscr)
{
scrHeight = height;
scrWidth = width;
scrFileName = file;
wScroller=wscr;
}

what should I do for trasprenting widget in that context.

[wysota]

and in the third f3 child widget I want to play scrolling text like news with transparent background.

I have a widget for that...

[ashukla]

I have a widget for that...

Dear Sir!

What is the full feature of that widget?
How to get this widget?

[wysota]

It's a widget that scrolls a QTextDocument. I haven't tried it with a transparent background, but it's probably possible

The widget is not available for public, I have some issues with speed stability I need to fix before releasing it. But in general I render the document to a pixmap and then render the pixmap to the widget with different offsets, depending on the step of the animation.

[ashukla]

It's a widget that scrolls a QTextDocument. I haven't tried it with a transparent background, but it's probably possible

The widget is not available for public, I have some issues with speed stability I need to fix before releasing it. But in general I render the document to a pixmap and then render the pixmap to the widget with different offsets, depending on the step of the animation.

OK Sir!
But In my context; How a way I set the transparency of widget.

[wysota]

I think J-P already gave you some hints. Did you follow them?

[ashukla]

I think J-P already gave you some hints. Did you follow them?

Yes! I have followed them. But I am not getting the desired output.

[wysota]

What is the desired output? Do you want to show it over another widget or over desktop?

[ashukla]

What is the desired output? Do you want to show it over another widget or over desktop?

Dear Sir!
I have explained earlier as follows

I have designed three QX11EmbedContainer widget (as a child namely f1,f2,f3 dynamically) of QX11Container parent widget. I am playing in f1 & f2 frames different movies and in the third f3 child widget I want to play scrolling text like news with transparent background.
for which I am using the above code.

I want to play scroll text upon the running movie background.
That means I want to play text scroller with tranparent background.
What should I do for that?
Thanking in advance to give suggestion!

[ashukla]

I want to show it over another widget.

[wysota]

It might not work, because the embedded widget is really another application, so drawing over it might be difficult. And because that other widget is a movie, it might be even more difficult - usually one uses overlays for that. I suggest you find some other solution (for example don't embed external applications).

[pbutterworth]

Hi, I am attempting the same thing, but simpler.
I would like to place a QGraphicsView over the top of (a child of) another plain QWidget. I have tried:

#include <QtGui>
 
int main(int argc, char *argv[])
{
QApplication app(argc, argv);
QMainWindow window;
 
QGraphicsScene* scene = new QGraphicsScene(&window);
QGraphicsItem* item = scene->addText("QGraphicsTextItem");
item->setFlags(QGraphicsItem::ItemIsMovable);
 
QGraphicsView* view = new QGraphicsView(&window);
view->setStyleSheet("background: transparent");
view->setScene(scene);
 
window.setCentralWidget(view);
window.setStyleSheet("background: green");
window.show();
return app.exec();
}

#include <QtGui>

int main(int argc, char *argv[])
{
QApplication app(argc, argv);
QMainWindow window;

QGraphicsScene* scene = new QGraphicsScene(&window);
QGraphicsItem* item = scene->addText("QGraphicsTextItem");
item->setFlags(QGraphicsItem::ItemIsMovable);

QGraphicsView* view = new QGraphicsView(&window);
view->setStyleSheet("background: transparent");
view->setScene(scene);

window.setCentralWidget(view);
window.setStyleSheet("background: green");
window.show();
return app.exec();
}

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but it results in a white window, not a green one. The QGraphicsView refuses to become transparent.

I've tried this in Qt for win32 4.4.0 and 4.4.3.
Anyone have any ideas? Thanks!

[bowdar]

QBrush brBrush;
 
    QPalette palette(brBrush,brBrush,brBrush,brBrush,brBrush,brBrush,brBrush,brBrush,brBrush);
 
    setPalette(palette);
 
    setWindowFlags(Qt::FramelessWindowHint | Qt::WindowSystemMenuHint);
 
    setAttribute(Qt::WA_TranslucentBackground);
 
    setFrameShape(QFrame::NoFrame);

QBrush brBrush;

    QPalette palette(brBrush,brBrush,brBrush,brBrush,brBrush,brBrush,brBrush,brBrush,brBrush);

    setPalette(palette);

    setWindowFlags(Qt::FramelessWindowHint | Qt::WindowSystemMenuHint);

    setAttribute(Qt::WA_TranslucentBackground);

    setFrameShape(QFrame::NoFrame);

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try this, with Qt 4.5

[totem]

Hi,

I encounter the same issue. Thanks to jpn answer i managed to see the mainwindow background under my graphicsview.
Now, is there an easy way to make the central widget transparent. I mean : to obtain a QMainWindow with toolbar and menubar and borders, but where we see desktop and other windows in place of central widget. I'm looking for a solution for some times now but can't find anything helpful

Note : in my app, this would allow the user to draw something, using the QGraphicsView as a tracing paper