* Add nullable annotations...
...to `AvaloniaObject`/`AvaloniaProperty`-related classes and a few other uncontroversial files.
* Check for null before first use.
* Don't need this check as base class does it.
- Pass information for all property changes to `OnPropertyChangedCore`; whether they result in an effective value change or not
- Added `GetBaseValue` to get a value with a specified priority
- Change the signature of `OnPropertyChanged` again to take an `AvaloniaPropertyChangedEventArgs<T>`
Previously it wasn't clear which constructor on `InstancedBinding` must be called for a particular binding mode. Refactored the constructors:
- We now have a single public ctor which takes an `ISubject`, as a subject can be used for all binding modes.
- Instanced bindings with other sources such as single values and `IObservables` are now constructed via static methods which only allow the correct sources for that binding mode
We're going to say that for the moment only direct properties handle
data validation. This gets around a few thorny issues with data
validation on styled properties.
This is needed so that things like the following can be done:
<TreeView>
<TreeView.Styles>
<Style Selector="TreeViewItem">
<Setter Property="IsExpanded" Value="{Binding IsExpanded}"/>
</Style>
</TreeView.Styles>
<TreeView>
(At the moment we have TreeDataTemplate.IsExpanded but this isn't good
enough: it only supports setting IsExpanded on creation of the item with
no binding.)
With this commit, setters can now contain bindings, but they aren't yet
applied correctly. As part of this commit, classes related to binding
have been moved to the Perspex.Data namespace.