[Development] QtQuick transparent toplevel window broken in dev?

[Nils Jeisecke]

Hi list,

while playing around with a recent build of dev
(82bdc55bc36f8a785e2637b01cb91d361b01fc29), I've noticed that toplevel
window transparency for QQuickWindow seems to have stopped working (at
least on macOS, haven't tried Windows so far).

Any "ApplicationWindow" with color: "transparent" should illustrate the
problem but I simply tried the "pure qml" example from this
stackoverflow entry:

https://stackoverflow.com/questions/22554796/qtquick-2-transparent-window-background

Window is transparent with 5.9 but opaque with dev.

Setting QQuickWindow::setDefaultAlphaBuffer(true) before creating any
window does not help and is not necessary on 5.9 anyway.

Did some regression creep in?

Nils