DragStartingContext IDragDropElement.DragStarting(DragDropTrigger trigger, object initializeContext)
{
var dragVisual = this.ParentGrid.DragBehavior.GetReorderVisual(this);
if (dragVisual == null)
{
DataGridFlyoutHeader header = this.CreateHeader();
dragVisual = header;
}
// TODO: Consider exposing this through separate control.
dragVisual.DataContext = this.DataContext;
this.Opacity = 0.0;
var surface = this.OnDragSurfaceRequested();
var payload = new ReorderItemsDragOperation(this);
this.ParentGrid.DragBehavior.OnReorderStarted(this.DataContext as GroupDescriptorBase);
return(new DragStartingContext {
DragVisual = dragVisual, Payload = payload, DragSurface = surface, HitTestStrategy = new ColumnHeaderHittestStrategy(this, surface.RootElement)
});
}
private bool ShouldReorder(Point position, ReorderItemsDragOperation data)
{
if (this.reorderCoordinator == null)
{
return(false);
}
var sourceElement = this.reorderCoordinator.Host.ElementAt(data.CurrentSourceReorderIndex) as DataGridColumnHeader;
bool draggingFromRight = position.X >= this.ActualWidth / 2 + DragInitializer.DefaultStartTreshold && position.X <= this.ActualWidth && this.logicalIndex > data.CurrentSourceReorderIndex;
bool draggingFromLeft = position.X <= this.ActualWidth / 2 - DragInitializer.DefaultStartTreshold && position.X >= 0 && this.logicalIndex < data.CurrentSourceReorderIndex;
bool canReorderColumn = sourceElement != null && this.Owner.DragBehavior.CanReorder(sourceElement.Column, this.Column);
return(canReorderColumn && (draggingFromLeft || draggingFromRight));
}