private bool IsValidDrop(DragEventArgs e, out DropInfo dropInfo)
{
dropInfo = null;
IDataSourceViewModel viewModel = e.Data.GetData(typeof (SingleDataSourceViewModel)) as IDataSourceViewModel ??
e.Data.GetData(typeof (MergedDataSourceViewModel)) as IDataSourceViewModel;
var source = new TreeItem
{
ViewModel = viewModel
};
if (source.ViewModel == null)
return false;
TreeItem dropTarget = GetDataSourceFromPosition(e.GetPosition(_partDataSources));
if (dropTarget == null)
return false;
DataSourceDropType dropType = GetDropType(e, dropTarget, viewModel);
var model = (MainWindowViewModel) DataContext;
IDataSourceViewModel group;
if (!model.CanBeDropped(source.ViewModel, dropTarget.ViewModel, dropType, out group))
return false;
dropInfo = new DropInfo
{
Source = source,
Type = dropType,
Target = dropTarget,
TargetGroup = new TreeItem
{
ViewModel = group,
TreeViewItem = GetTreeViewItem(group)
}
};
return true;
}
private DataSourceDropType GetDropType(DragEventArgs e,
TreeItem destination,
IDataSourceViewModel source)
{
if (destination == null)
return DataSourceDropType.None;
Point pos = e.GetPosition(destination.TreeViewItem);
var dropType = DataSourceDropType.None;
double height = destination.TreeViewItem.ActualHeight;
if (source is SingleDataSourceViewModel)
{
// Let's distribute it as follows:
// 20% top => arrange
// 60% middle => group
// 20% bottom => arrange
//
// This way 60% of the height is used for grouping and 40% is used for arranging.
if (pos.Y < height*0.2)
dropType |= DataSourceDropType.ArrangeTop;
else if (pos.Y < height*0.8)
dropType |= DataSourceDropType.Group;
else
dropType |= DataSourceDropType.ArrangeBottom;
if (destination.ViewModel.Parent != null)
dropType |= DataSourceDropType.Group;
}
else
{
// Groups can't be grouped any further, thus we
// simply arrange it above or beneath the drop source
// at a 50/50 split.
if (pos.Y < height*0.5)
dropType |= DataSourceDropType.ArrangeTop;
else
dropType |= DataSourceDropType.ArrangeBottom;
}
return dropType;
}
