public Box(BoxViewModel viewModel, Caret caretPerTree)
{
this.DataContext = viewModel;
this.CaretPerTree = caretPerTree;
this.Focusable = true;
this.Width = double.NaN;
this.ShowGridLines = false;
//this.SizeChanged += (sender, e) => { if (this.BoxParent != null) this.BoxParent.InvalidateMeasure(); throw new NotImplementedException("You'd think this is automated in WPF"); };
this.viewModel.CaretPerTree.CaretChangedFocus += OnCaretChanged;
OnCaretChanged(this.viewModel.Caret, new PropertyChangedEventArgs(nameof(BoxViewModel.Caret)));
this.viewModel.Elements.CollectionChangedElementWise += OnElementsChanged;
//trigger adding the initial elements. THe viewModel argument may already have some elements set
if (viewModel.Elements.Count != 0)
{
var e = new NotifyBoxElementsChangedEventArgs(viewModel.Elements, NotifyCollectionChangedAction.Add, viewModel.Elements, 0);
OnElementsChanged(viewModel.Elements, e);
}
this.viewModel.PropertyChanged += OnFocusableChanged;
OnFocusableChanged(this.viewModel, new PropertyChangedEventArgs(nameof(BoxViewModel.Modifiable)));
this.viewModel.Selections.CollectionChanged += OnSelectionsChanged;
if (this.viewModel.Selections.Count != 0)
OnSelectionsChanged(this.viewModel.Selections, new NotifyCollectionChangedEventArgs(NotifyCollectionChangedAction.Add, this.viewModel.Selections, 0));
}
//Ok, so this is how this works.
//we start with the root view model. It's treated like any other box in the view model. We hook into the box collection changed. when a box composition is added to some box,
//the event handler is triggered and registers a mutation associated with that box. A mutation is a lazy change, meaning that whenever that box is requested, the mutation takes place
//This entails adding in the box composition to the name instance model and registering an eventhandler that handles subsequent changes to the box composition
//(from the moment of implementation the mutation that adds it, not before) TODO: consider the case where the box composition was removed already
//In case the box collection changed and added a glyph, again a mutation is added so that whenever the box is requested, the glyph gets added.
//The case for the box composition collection changed event handler is pretty symmetric. When a box is added, it registers a mutation with the box composition.
//whenever the box composition is requested, the mutation takes effect: it adds the box and hooks into its collection changed event.
//removal works in the same manner, adding mutations that remove the boxes/box compositions and their respective handlers (and of all descendents as well).
private void onBoxElementsCollectionChanged(object boxElements, NotifyBoxElementsChangedEventArgs e)
{
var elements = (BoxElementsCollection)boxElements;
switch (e.Action)
{
case NotifyCollectionChangedAction.Add:
e.NewItems.VirtualForeach
(
(BoxCompositionViewModel newBoxComposition, int i) => this.AddNewBoxCompositionMutation(newBoxComposition, e.NewStartingIndex + i),
(Glyph newGlyphRun, int i) => this.AddNewGlyphsMutation(newGlyphRun, e.NewStartingIndex + i, elements.Box)
);
break;
case NotifyCollectionChangedAction.Remove:
this.Without(elements.Box, e.OldStartingIndex, e.OldItems);
break;
case NotifyCollectionChangedAction.Reset:
throw new ArgumentException("Use remove all, since otherwise I cannot access the removed elements");
default:
throw new NotImplementedException();
}
}