window() may be null. We check for that, but 5a3ef9e825 introduced code that uses window() before the check.
Move the check before the relevant code to fix that
BUG: 456094
BUG: 457690
`enabled` must be set in the backend because `visible` will always be
true after getting a valid nodeId, and sometimes we need to reset `enabled`
to false.
CCBUG: 449189
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.