private Boolean CheckIfValidDrop(TreeViewItemDropEventArgs tviea)
{
SwagOption targetOpt = (SwagOption)tviea.TargetItem.DataContext;
SwagOption droppedOpt = (SwagOption)tviea.DroppedItem.DataContext;
Boolean valid = true;
MoveType moveType = GetMoveType(tviea);
SwagOption tempOpt = targetOpt.Parent;
while (valid && tempOpt != null)
{
if (droppedOpt == tempOpt) //Don't drop within own descendants
{
valid = false;
break;
}
tempOpt = tempOpt.Parent;
}
if (!valid)
{
tviea.DragEventArgs.Effects = DragDropEffects.None;
tviea.DragEventArgs.Handled = true;
}
return(valid);
}
private Boolean CheckIfValidDrop(TreeViewItemDropEventArgs tviea)
{
BooleanExpression targetExp = (BooleanExpression)tviea.TargetItem.DataContext;
BooleanExpression droppedExp = (BooleanExpression)tviea.DroppedItem.DataContext;
Boolean valid = true;
MoveType moveType = GetMoveType(tviea);
if ((targetExp == RootExpression && (moveType == MoveType.Above || moveType == MoveType.Below)) || //Don't drop as root sibling
targetExp == droppedExp) //Don't drop to self
{
valid = false;
}
BooleanExpression tempExp = targetExp.Parent;
while (valid && tempExp != null)
{
if (droppedExp == tempExp) //Don't drop within own descendants
{
valid = false;
break;
}
tempExp = tempExp.Parent;
}
if (!valid)
{
tviea.DragEventArgs.Effects = DragDropEffects.None;
tviea.DragEventArgs.Handled = true;
}
return(valid);
}
private void SwagItemsControl_TreeViewItemDropPreview(object sender, RoutedEventArgs e)
{
TreeViewItemDropEventArgs tviea = (TreeViewItemDropEventArgs)e;
if (!CheckIfValidDrop(tviea))
{
return;
}
Boolean allowChildMove = false, allowSiblingMove = false;
switch (tviea.TargetItem.DataContext)
{
case BooleanOperationExpression opExp:
allowChildMove = true;
allowSiblingMove = true;
break;
case BooleanBooleanVariableExpression bbvExp:
allowSiblingMove = true;
break;
case BooleanStringVariableExpression bsvExp:
allowSiblingMove = true;
break;
}
tviea.TargetItem.BorderBrush = (Brush)this.FindResource("MahApps.Brushes.Text");
MoveType moveType = GetMoveType(tviea);
switch (moveType)
{
case MoveType.Above:
if (allowSiblingMove)
{
tviea.TargetItem.BorderThickness = new Thickness(0, 1, 0, 0);
}
break;
case MoveType.Below:
if (allowSiblingMove)
{
tviea.TargetItem.BorderThickness = new Thickness(0, 0, 0, 1);
}
break;
case MoveType.Into:
if (allowChildMove)
{
tviea.TargetItem.BorderThickness = new Thickness(1, 0, 0, 0);
}
else
{
tviea.DragEventArgs.Effects = DragDropEffects.None;
tviea.DragEventArgs.Handled = true;
}
break;
}
}
private void ControlTreeView_PreviewDragLeave(object sender, DragEventArgs e)
{
if (AllowMove)
{
TreeViewItem targetItem = ((DependencyObject)e.OriginalSource).TryFindParent <TreeViewItem>();
if (targetItem != null)
{
RoutedEventArgs ea = new TreeViewItemDropEventArgs(SwagItemsControl.TreeViewItemLeavePreviewEvent, e, targetItem, null);
RaiseEvent(ea);
}
}
}
private void ControlTreeView_Drop(object sender, DragEventArgs e)
{
if (AllowMove)
{
TreeViewItem targetItem = ((DependencyObject)e.OriginalSource).TryFindParent <TreeViewItem>();
TreeViewItem droppedItem = (TreeViewItem)e.Data.GetData("TreeViewItemDrop");
if (targetItem != null && droppedItem != null)
{
RoutedEventArgs ea = new TreeViewItemDropEventArgs(SwagItemsControl.TreeViewItemDropEvent, e, targetItem, droppedItem);
RaiseEvent(ea);
}
}
}
private MoveType GetMoveType(TreeViewItemDropEventArgs tviea)
{
MoveType moveType = MoveType.None;
FrameworkElement header = tviea.TargetItem.FindVisualChild <FrameworkElement>("PART_Header");
Point p = tviea.DragEventArgs.GetPosition(header);
Double quarter = header.ActualHeight / 4;
if (p.Y + 2 < quarter * 1)
{
moveType = MoveType.Above;
}
else if (p.Y - 2 > quarter * 3)
{
moveType = MoveType.Below;
}
else
{
moveType = MoveType.Into;
}
return(moveType);
}
private void SwagItemsControl_TreeViewItemLeavePreview(object sender, RoutedEventArgs e)
{
TreeViewItemDropEventArgs tviea = (TreeViewItemDropEventArgs)e;
tviea.TargetItem.BorderThickness = new Thickness(0, 0, 0, 0);
}
private void SwagItemsControl_TreeViewItemDrop(object sender, RoutedEventArgs e)
{
TreeViewItemDropEventArgs tviea = (TreeViewItemDropEventArgs)e;
tviea.TargetItem.BorderThickness = new Thickness(0, 0, 0, 0);
if (!CheckIfValidDrop(tviea)) //Drops are still possible because TreeViewItemDropPreview can be skipped
{
return;
}
MoveType moveType = GetMoveType(tviea);
SwagOption targetOpt = (SwagOption)tviea.TargetItem.DataContext;
SwagOption droppedOpt = (SwagOption)tviea.DroppedItem.DataContext;
SwagOptionGroup originalDroppedParent = (SwagOptionGroup)droppedOpt.Parent;
Boolean sameParent = originalDroppedParent == targetOpt.Parent;
Int32 originalDroppedSequence = droppedOpt.Sequence,
currentDroppedSequence = droppedOpt.Sequence,
targetSequence = targetOpt.Sequence,
delta = targetSequence - originalDroppedSequence;
switch (moveType)
{
case MoveType.Above:
case MoveType.Below:
if (!sameParent)
{
originalDroppedParent.Children.Remove(droppedOpt);
droppedOpt.Sequence = -1; //reset sequence
targetOpt.Parent.Children.Add(droppedOpt);
currentDroppedSequence = droppedOpt.Sequence;
delta = targetSequence - currentDroppedSequence;
}
switch (moveType)
{
case MoveType.Above:
if (delta != 0)
{
foreach (SwagOption sibling in targetOpt.Parent.Children)
{
if (sibling.Sequence >= Math.Min(currentDroppedSequence, targetSequence) && sibling.Sequence < Math.Max(currentDroppedSequence, targetSequence))
{
sibling.Sequence = (sibling.Sequence + (delta > 0 ? -1 : 1));
}
}
droppedOpt.Sequence = targetSequence + (delta > 0 ? -1 : 0);
if (targetOpt.Parent == null)
{
CollectionViewSource.GetDefaultView(OptionCollection).Refresh();
}
else
{
CollectionViewSource.GetDefaultView(targetOpt.Parent.Children).Refresh();
}
}
break;
case MoveType.Below:
if (delta != 0)
{
foreach (SwagOption sibling in targetOpt.Parent.Children)
{
if (sibling.Sequence > Math.Min(currentDroppedSequence, targetSequence) && sibling.Sequence <= Math.Max(currentDroppedSequence, targetSequence))
{
sibling.Sequence = (sibling.Sequence + (delta > 0 ? -1 : 1));
}
}
droppedOpt.Sequence = targetSequence + (delta > 0 ? 0 : 1);
if (targetOpt.Parent == null)
{
CollectionViewSource.GetDefaultView(OptionCollection).Refresh();
}
else
{
CollectionViewSource.GetDefaultView(targetOpt.Parent.Children).Refresh();
}
}
break;
}
break;
case MoveType.Into:
if (tviea.TargetItem.DataContext is SwagOptionGroup grp)
{
originalDroppedParent.Children.Remove(droppedOpt);
droppedOpt.Sequence = -1; //reset sequence
grp.Children.Add(droppedOpt);
}
break;
}
}