virtual [EStretchResult](API\Editor\SequencerCore\MVVM\Extensions\UE__Sequencer__EStretchResult) OnBeginStretch ( const [IStretchOperation](API\Editor\SequencerCore\MVVM\Extensions\IStretchOperation) & StretchOperation, const [FStretchScreenParameters](API\Editor\SequencerCore\MVVM\Extensions\FStretchScreenParameters) & ScreenParameters, [FStretchParameters](API\Editor\SequencerCore\MVVM\Extensions\FStretchParameters) * InOutParameters )