public UIActionState TryDemoteActiveVariation(bool perform)
{
// Find the first move in this variation which has a 'less important' side line.
Variation moveWithSideLine = game.ActiveTree.ParentVariation;
while (moveWithSideLine != null &&
moveWithSideLine.VariationIndex + 1 == moveWithSideLine.ParentTree.Variations.Count)
{
moveWithSideLine = moveWithSideLine.ParentTree.ParentVariation;
}
if (moveWithSideLine == null)
{
// Already no sidelines below this one.
return(UIActionVisibility.Disabled);
}
if (perform)
{
moveWithSideLine.RepositionAfter(moveWithSideLine.VariationIndex + 1);
GameUpdated();
}
return(UIActionVisibility.Enabled);
}