[QtEmbedded] Translucent QGraphicsView with animated child widgets

[wysota]

In that case I'd assume your device doesn't allow you to use translucency.

Please post your problem in the right section of the forum next time.

[zuck]

I'm sorry.

Well, currently the test is running on QVFB and not on the final device.

I've tried to run it with Qt x11 and the result is a window with a black background (the rectangle doesn't paint the trail but the background is fully opaque).

[wysota]

I've tried to run it with Qt x11 and the result is a window with a black background (the rectangle doesn't paint the trail but the background is fully opaque).

It probably means you have composition extension disabled in your X config. Run xdpyinfo and check if Composite is reported as one of the extensions.

[zuck]

Yes, I have it:

number of extensions:    30
    BIG-REQUESTS
    Composite <----------
    DAMAGE
    DOUBLE-BUFFER
    DPMS
    DRI2
    GLX
    Generic Event Extension
    MIT-SCREEN-SAVER
    MIT-SHM
    NV-CONTROL
    NV-GLX
    RANDR
    RECORD
    RENDER
    SECURITY
    SHAPE
    SYNC
    X-Resource
    XC-MISC
    XFIXES
    XFree86-DGA
    XFree86-VidModeExtension
    XINERAMA
    XINERAMA
    XInputExtension
    XKEYBOARD
    XTEST
    XVideo
    XVideo-MotionCompensation

number of extensions:    30
    BIG-REQUESTS
    Composite <----------
    DAMAGE
    DOUBLE-BUFFER
    DPMS
    DRI2
    GLX
    Generic Event Extension
    MIT-SCREEN-SAVER
    MIT-SHM
    NV-CONTROL
    NV-GLX
    RANDR
    RECORD
    RENDER
    SECURITY
    SHAPE
    SYNC
    X-Resource
    XC-MISC
    XFIXES
    XFree86-DGA
    XFree86-VidModeExtension
    XINERAMA
    XINERAMA
    XInputExtension
    XKEYBOARD
    XTEST
    XVideo
    XVideo-MotionCompensation

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[wysota]

The code I gave you works on my system (Linux 2.6 + KDE4 + Qt 4.6). So if it doesn't work on yours, this has to be a hardware or software configuration issue on your end.

[zuck]

Ok, thanks!

[zuck]

It now works on X11 with xcompmgr activated, but it still remains bugged on Qt Embedded

[wysota]

Because you have no compositing support there. It simply won't work. You can use QPixmap::grabWidget() to grab the image of the content beneath and render it as background of your widget above.

[zuck]

Yeah! This is the final working code (Qt 4.6):

#include <QtGui/QDesktopWidget>
#include <QtGui/QApplication>
 
MainWindow::MainWindow(QWidget* parent)
    :   QmlView(parent) // or QGraphicsView...
{
    this->setWindowFlags(Qt::FramelessWindowHint);
    this->setCacheMode(QGraphicsView::CacheBackground);
}
 
void MainWindow::showEvent(QShowEvent* event)
{ 
    WId wid = QApplication::desktop()->winId();
 
    int x = this->x();
    int y = this->y();
    int w = this->width();
    int h = this->height();
 
    this->setBackgroundBrush(QPixmap::grabWindow(wid, x, y, w, h));
 
    QmlView::showEvent(event);
}

#include <QtGui/QDesktopWidget>
#include <QtGui/QApplication>

MainWindow::MainWindow(QWidget* parent)
    :   QmlView(parent) // or QGraphicsView...
{
    this->setWindowFlags(Qt::FramelessWindowHint);
    this->setCacheMode(QGraphicsView::CacheBackground);
}

void MainWindow::showEvent(QShowEvent* event)
{ 
    WId wid = QApplication::desktop()->winId();
    
    int x = this->x();
    int y = this->y();
    int w = this->width();
    int h = this->height();
    
    this->setBackgroundBrush(QPixmap::grabWindow(wid, x, y, w, h));

    QmlView::showEvent(event);
}

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No "WA_TranslucentBackground" or "autoFillBackground(false)" are needed!