If there's no texture factory function, return the old node immediately.
Also, remove a guard against the code that calculates centered geometry
of the texture node. We cannot hit that case as we check whether the
factory function has returned a valid texture before that.
Tell QQuickWindow when there is an alpha channel, otherwise it's
considered opaque and Qt/mesa renders it disregarding what's underneath.
Sometimes windows will have translucent areas and we want these to be
rendered cleanly on top of the scene. Alternatively it shows weird
noise.
Alexander Lohnau
Aleix Pol
Vlad Zahorodnii