[Development] How to set QQuickView TranslucentBackground

[Samuel Rødal]

On 03/08/2012 02:24 PM, ext hailong geng wrote:
> Hi
> Thank you for your reply. What do you mean by "setting a non-zero
> alpha in the QSurfaceFormat of the QWindow"? I tried touse the following
> code but still get black background.
> QQuickViewcanvas;
>
>      QSurfaceFormat  surfaceFormat;
>
>      surfaceFormat.setAlphaBufferSize(1000);

Should probably be surfaceFormat.setAlphaBufferSize(8); as I'm not sure 
if it bails out when it can't find a configuration with at minimum the 
requested buffer size at the moment.

>      canvas.setFormat(surfaceFormat);
>
>      canvas.setClearBeforeRendering(true);
>
>      canvas.setClearColor(QColor(Qt::transparent));
>
>      canvas.setWindowFlags(Qt::FramelessWindowHint);

Looks good, I'd expect this to give the expected outcome. Try the alpha 
buffer fix, and if it still doesn't work please file a bug. It might be 
that noone has tested this properly with Qt 5 yet.

> Would you please tell me something about how does Qt Quick2 render the
> scene? I think it doesn't render opengl into video memory
> directly because if so, when I drag one other window above the qml
> scene, it should flash :) So does it use QGLPixelBuffer class for that?
> I am new to opengl and scene graph, I am not clear with the work flow.
> But I really want to make the QML View Translucent, this will be very
> cool ^_^

It does render directly to the window (although potentially in a 
separate thread), not sure what kind of flashing you expect, that's 
mostly solved by compositing window managers.


--
Samuel