A QWindow may be created() and destroyed() multiple times in the lifetime
of the window, each time resulting in a new platform window (QIOSWindow)
being created. This QIOSWindow is backed by a new UIView each time, hence
it needs a new FBO and renderbuffer-mapping, since the previous
renderbuffer was mapped to the old UIView.
This fixes a bug where a QWindow would not render after a destroy()
unless it was resized (which triggered new FBO/renderbuffers).
We need to inherit QObject so that we can watch the destroyed() signal.
Change-Id: I93172dd6280b86b49755bf7abddf061d7e6b66f1
Reviewed-by: Richard Moe Gustavsen <richard.gustavsen@digia.com>
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