Better document attaching a QFutureWatcher to a started QFuture

It is an important and useful part of the API contract that the
QFutureWatcher signals will emit complete information after
setFuture() on an already started QFuture. If that wasn't so, some
API clients would need two code paths to gather state and progress
information: one through the signals for not yet started QFutures,
and one through the state querying APIs for already started
QFutures.

The previous documentation was not precise enough to rely on, even
though the implemented behavior - cf.
QFutureInterfaceBasePrivate::connectOutputInterface() -
seems well thought out and implemented to rely on.

Pick-to: 6.3 6.2
Change-Id: Iaf3db37a851f07ac85881adaea5c83612a7fd843
Reviewed-by: Leena Miettinen <riitta-leena.miettinen@qt.io>
Reviewed-by: Sona Kurazyan <sona.kurazyan@qt.io>

0 files changed, 0 insertions, 0 deletions