[Qt5] How to make a QQuickView TranslucentBackground?

[weiyuemin]

I want to use setAttribute(Qt::WA_TranslucentBackground), it used to be a method of QDeclarativeView in Qt4.8.3.

When I replace QDeclarativeView with QQuickView, the setAttribute method disappears..

I noticed that QQuickView is inherited from QQuickWindow, it seemed not related with QWidget, when the old QDeclarativeView is indirectly inherited from QWidget( setAttribute is a method of QWidget ).

So in Qt5 how can I implement a TranslucentBackground window that using qml? (Meanwhile I want to use QtQuick 2.0)

Thank you !

[billouparis]

this code works for me under Ubuntu 12.10

@#include <QtGui/QGuiApplication>
#include "qtquick2applicationviewer.h"
#include <QDebug>

int main(int argc, char *argv[])
{
QGuiApplication app(argc, argv);

QtQuick2ApplicationViewer viewer;
viewer.setSurfaceType(QSurface::OpenGLSurface);

QSurfaceFormat format;
format.setAlphaBufferSize(8);
format.setRenderableType(QSurfaceFormat::OpenGL);
qDebug() <&lt; format.hasAlpha();
viewer.setFormat(format);

QColor color;
color.setRedF(0.0);
color.setGreenF(0.0);
color.setBlueF(0.0);
color.setAlphaF(0.0);
viewer.setColor(color);

viewer.setClearBeforeRendering(true);

//viewer.setFlags(Qt::FramelessWindowHint);

viewer.setMainQmlFile&#40;QStringLiteral("qml/MaskTest/main.qml"&#41;);
viewer.showExpanded();

return app.exec();

}
@

Hope it helps
Bill

[weiyuemin]

Thank you Bill,
Follow your code, I write this:

@
int main(int argc, char *argv[])
{
QScopedPointer<QGuiApplication> app(new QGuiApplication(argc, argv));

QQuickView view;

view.setSurfaceType(QSurface::OpenGLSurface);

QSurfaceFormat format;
//QSurfaceFormat format = view.format();
format.setAlphaBufferSize(8);
format.setRenderableType(QSurfaceFormat::OpenGL);
qDebug() <&lt; format.hasAlpha();
view.setFormat(format);

QColor color;
color.setRedF(0.0);
color.setGreenF(0.0);
color.setBlueF(0.0);
color.setAlphaF(0.0);
view.setColor(color);

view.setClearBeforeRendering(true);

view.connect(view.engine(), SIGNAL(quit()), SLOT(close()));  
view.setFlags(Qt::FramelessWindowHint);

view.setSource(QUrl::fromLocalFile&#40;"qml/test.qml"&#41;);

view.show();

return app->exec();
}
@

the program will crash when executing app->exec(), it said:

ASSERT: "context" in file opengl\qopenglfunctions.cpp, line 194

then I pressed alt+esc, it poped another error:

ASSERT failure in QSGNode::appendChildNode: "QSGNode already has a parent", file scenegraph\coreapi\qsgnode.cpp, line 404

Comment view.setFormat(format); would make the program running without crash, but it's not transparent. The area should be transparent now is in black color.

I'm using WinXP.

The remaining problem is why I can't call setFormat method. Is there anyone facing the same problem?

[weiyuemin]

According to this issue, https://bugreports.qt-project.org/browse/QTBUG-28214
Transparent OpenGL windows are currently not supported on Windows?

[billouparis]

You might find the beginning of a solution in this topic:
http://qt-project.org/forums/viewthread/18984/

In windows XP, the issues might be related to:
-windows XP window manager itself (as in Windows 7)
-the way you compiled your qt5, don't forget to use option -opengl if you want to use your video hardware.

Regards,
Bill

[weiyuemin]

Thank you Bill, I will try to compile Qt5 with opengl and report my results here.

[weiyuemin]

I compiled with -opengl desktop. Now using your code, the program will not crash, but still not transparent. The area should be transparent has a black background.

So it is because transparent OpenGL windows are not supported on Windows?

[diorahman]

Interesting, what we have now?