/// <summary>
/// Applies a binding subject to a property on an instance.
/// </summary>
/// <param name="target">The target instance.</param>
/// <param name="property">The target property.</param>
/// <param name="subject">The binding subject.</param>
internal void Bind(IAvaloniaObject target, AvaloniaProperty property, ISubject <object> subject)
{
var mode = Mode == BindingMode.Default ?
property.GetMetadata(target.GetType()).DefaultBindingMode : Mode;
switch (mode)
{
case BindingMode.Default:
case BindingMode.OneWay:
target.Bind(property, subject, Priority);
break;
case BindingMode.TwoWay:
throw new NotSupportedException("TwoWay MultiBinding not currently supported.");
case BindingMode.OneTime:
target.GetObservable(Control.DataContextProperty).Subscribe(dataContext =>
{
subject.Take(1).Subscribe(x => target.SetValue(property, x, Priority));
});
break;
case BindingMode.OneWayToSource:
target.GetObservable(property).Subscribe(subject);
break;
}
}
/// <summary>
/// Applies an <see cref="InstancedBinding"/> a property on an <see cref="IAvaloniaObject"/>.
/// </summary>
/// <param name="target">The target object.</param>
/// <param name="property">The property to bind.</param>
/// <param name="binding">The instanced binding.</param>
/// <param name="anchor">
/// An optional anchor from which to locate required context. When binding to objects that
/// are not in the logical tree, certain types of binding need an anchor into the tree in
/// order to locate named controls or resources. The <paramref name="anchor"/> parameter
/// can be used to provide this context.
/// </param>
/// <returns>An <see cref="IDisposable"/> which can be used to cancel the binding.</returns>
public static IDisposable Apply(
IAvaloniaObject target,
AvaloniaProperty property,
InstancedBinding binding,
object anchor)
{
Contract.Requires <ArgumentNullException>(target != null);
Contract.Requires <ArgumentNullException>(property != null);
Contract.Requires <ArgumentNullException>(binding != null);
var mode = binding.Mode;
if (mode == BindingMode.Default)
{
mode = property.GetMetadata(target.GetType()).DefaultBindingMode;
}
switch (mode)
{
case BindingMode.Default:
case BindingMode.OneWay:
return(target.Bind(property, binding.Observable ?? binding.Subject, binding.Priority));
case BindingMode.TwoWay:
return(new CompositeDisposable(
target.Bind(property, binding.Subject, binding.Priority),
target.GetObservable(property).Subscribe(binding.Subject)));
case BindingMode.OneTime:
var source = binding.Subject ?? binding.Observable;
if (source != null)
{
return(source
.Where(x => BindingNotification.ExtractValue(x) != AvaloniaProperty.UnsetValue)
.Take(1)
.Subscribe(x => target.SetValue(property, x, binding.Priority)));
}
else
{
target.SetValue(property, binding.Value, binding.Priority);
return(Disposable.Empty);
}
case BindingMode.OneWayToSource:
return(Observable.CombineLatest(
binding.Observable,
target.GetObservable(property),
(_, v) => v)
.Subscribe(x => binding.Subject.OnNext(x)));
default:
throw new ArgumentException("Invalid binding mode.");
}
}
/// <summary>
/// Gets an observable for a <see cref="AvaloniaProperty"/>.
/// </summary>
/// <param name="o">The object.</param>
/// <typeparam name="T">The property type.</typeparam>
/// <param name="property">The property.</param>
/// <returns>
/// An observable which fires immediately with the current value of the property on the
/// object and subsequently each time the property value changes.
/// </returns>
public static IObservable <T> GetObservable <T>(this IAvaloniaObject o, AvaloniaProperty <T> property)
{
Contract.Requires <ArgumentNullException>(o != null);
Contract.Requires <ArgumentNullException>(property != null);
return(o.GetObservable((AvaloniaProperty)property).Cast <T>());
}
/// <summary>
/// Applies an <see cref="InstancedBinding"/> a property on an <see cref="IAvaloniaObject"/>.
/// </summary>
/// <param name="target">The target object.</param>
/// <param name="property">The property to bind.</param>
/// <param name="binding">The instanced binding.</param>
/// <param name="anchor">
/// An optional anchor from which to locate required context. When binding to objects that
/// are not in the logical tree, certain types of binding need an anchor into the tree in
/// order to locate named controls or resources. The <paramref name="anchor"/> parameter
/// can be used to provice this context.
/// </param>
/// <returns>An <see cref="IDisposable"/> which can be used to cancel the binding.</returns>
public static IDisposable Apply(
IAvaloniaObject target,
AvaloniaProperty property,
InstancedBinding binding,
object anchor)
{
Contract.Requires<ArgumentNullException>(target != null);
Contract.Requires<ArgumentNullException>(property != null);
Contract.Requires<ArgumentNullException>(binding != null);
var mode = binding.Mode;
if (mode == BindingMode.Default)
{
mode = property.GetMetadata(target.GetType()).DefaultBindingMode;
}
switch (mode)
{
case BindingMode.Default:
case BindingMode.OneWay:
return target.Bind(property, binding.Observable ?? binding.Subject, binding.Priority);
case BindingMode.TwoWay:
return new CompositeDisposable(
target.Bind(property, binding.Subject, binding.Priority),
target.GetObservable(property).Subscribe(binding.Subject));
case BindingMode.OneTime:
var source = binding.Subject ?? binding.Observable;
if (source != null)
{
return source
.Where(x => BindingNotification.ExtractValue(x) != AvaloniaProperty.UnsetValue)
.Take(1)
.Subscribe(x => target.SetValue(property, x, binding.Priority));
}
else
{
target.SetValue(property, binding.Value, binding.Priority);
return Disposable.Empty;
}
case BindingMode.OneWayToSource:
return target.GetObservable(property).Subscribe(binding.Subject);
default:
throw new ArgumentException("Invalid binding mode.");
}
}
/// <summary>
/// Gets a subject for a <see cref="AvaloniaProperty"/>.
/// </summary>
/// <typeparam name="T">The property type.</typeparam>
/// <param name="o">The object.</param>
/// <param name="property">The property.</param>
/// <param name="priority">
/// The priority with which binding values are written to the object.
/// </param>
/// <returns>
/// An <see cref="ISubject{T}"/> which can be used for two-way binding to/from the
/// property.
/// </returns>
public static ISubject <T> GetSubject <T>(
this IAvaloniaObject o,
AvaloniaProperty <T> property,
BindingPriority priority = BindingPriority.LocalValue)
{
return(Subject.Create <T>(
Observer.Create <T>(x => o.SetValue(property, x, priority)),
o.GetObservable(property)));
}
private ExpressionObserver CreateDataContexObserver(
IAvaloniaObject target,
string path,
bool targetIsDataContext,
object anchor)
{
Contract.Requires <ArgumentNullException>(target != null);
if (!(target is IControl))
{
target = anchor as IControl;
if (target == null)
{
throw new InvalidOperationException("Cannot find a DataContext to bind to.");
}
}
if (!targetIsDataContext)
{
var update = target.GetObservable(Control.DataContextProperty)
.Skip(1)
.Select(_ => Unit.Default);
var result = new ExpressionObserver(
() => target.GetValue(Control.DataContextProperty),
path,
update,
EnableValidation);
return(result);
}
else
{
return(new ExpressionObserver(
target.GetObservable(Visual.VisualParentProperty)
.OfType <IAvaloniaObject>()
.Select(x => x.GetObservable(Control.DataContextProperty))
.Switch(),
path,
EnableValidation));
}
}
private IObservable <object> GetParentDataContext(IAvaloniaObject target)
{
// The DataContext is based on the visual parent and not the logical parent: this may
// seem unintuitive considering the fact that property inheritance works on the logical
// tree, but consider a ContentControl with a ContentPresenter. The ContentControl's
// Content property is bound to a value which becomes the ContentPresenter's
// DataContext - it is from this that the child hosted by the ContentPresenter needs to
// inherit its DataContext.
return(target.GetObservable(Visual.VisualParentProperty)
.Select(x =>
{
return (x as IAvaloniaObject)?.GetObservable(StyledElement.DataContextProperty) ??
Observable.Return((object)null);
}).Switch());
}
private ExpressionObserver CreateTemplatedParentObserver(
IAvaloniaObject target,
string path)
{
Contract.Requires <ArgumentNullException>(target != null);
var update = target.GetObservable(Control.TemplatedParentProperty)
.Skip(1)
.Select(_ => Unit.Default);
var result = new ExpressionObserver(
() => target.GetValue(Control.TemplatedParentProperty),
path,
update);
return(result);
}
/// <summary>
/// Gets a subject for a <see cref="AvaloniaProperty"/>.
/// </summary>
/// <typeparam name="T">The property type.</typeparam>
/// <param name="o">The object.</param>
/// <param name="property">The property.</param>
/// <param name="priority">
/// The priority with which binding values are written to the object.
/// </param>
/// <returns>
/// An <see cref="ISubject{T}"/> which can be used for two-way binding to/from the
/// property.
/// </returns>
public static ISubject <T> GetSubject <T>(
this IAvaloniaObject o,
AvaloniaProperty <T> property,
BindingPriority priority = BindingPriority.LocalValue)
{
// TODO: Subject.Create<T> is not yet in stable Rx : once it is, remove the
// AnonymousSubject classes from this file and use Subject.Create<T>.
var output = new Subject <T>();
var result = new AnonymousSubject <T>(
Observer.Create <T>(
x => output.OnNext(x),
e => output.OnError(e),
() => output.OnCompleted()),
o.GetObservable(property));
o.Bind(property, output, priority);
return(result);
}
private ExpressionObserver CreateDataContextObserver(
IAvaloniaObject target,
string path,
bool targetIsDataContext,
object anchor,
bool enableDataValidation)
{
Contract.Requires <ArgumentNullException>(target != null);
if (!(target is IStyledElement))
{
target = anchor as IStyledElement;
if (target == null)
{
throw new InvalidOperationException("Cannot find a DataContext to bind to.");
}
}
if (!targetIsDataContext)
{
var update = target.GetObservable(StyledElement.DataContextProperty)
.Skip(1)
.Select(_ => Unit.Default);
var result = new ExpressionObserver(
() => target.GetValue(StyledElement.DataContextProperty),
path,
update,
enableDataValidation);
return(result);
}
else
{
return(new ExpressionObserver(
GetParentDataContext(target),
path,
enableDataValidation));
}
}
/// <summary>
/// Applies an <see cref="InstancedBinding"/> a property on an <see cref="IAvaloniaObject"/>.
/// </summary>
/// <param name="target">The target object.</param>
/// <param name="property">The property to bind.</param>
/// <param name="binding">The instanced binding.</param>
/// <param name="anchor">
/// An optional anchor from which to locate required context. When binding to objects that
/// are not in the logical tree, certain types of binding need an anchor into the tree in
/// order to locate named controls or resources. The <paramref name="anchor"/> parameter
/// can be used to provide this context.
/// </param>
/// <returns>An <see cref="IDisposable"/> which can be used to cancel the binding.</returns>
public static IDisposable Apply(
IAvaloniaObject target,
AvaloniaProperty property,
InstancedBinding binding,
object?anchor)
{
_ = target ?? throw new ArgumentNullException(nameof(target));
_ = property ?? throw new ArgumentNullException(nameof(property));
_ = binding ?? throw new ArgumentNullException(nameof(binding));
var mode = binding.Mode;
if (mode == BindingMode.Default)
{
mode = property.GetMetadata(target.GetType()).DefaultBindingMode;
}
switch (mode)
{
case BindingMode.Default:
case BindingMode.OneWay:
if (binding.Observable is null)
{
throw new InvalidOperationException("InstancedBinding does not contain an observable.");
}
return(target.Bind(property, binding.Observable, binding.Priority));
case BindingMode.TwoWay:
if (binding.Subject is null)
{
throw new InvalidOperationException("InstancedBinding does not contain a subject.");
}
return(new TwoWayBindingDisposable(
target.Bind(property, binding.Subject, binding.Priority),
target.GetObservable(property).Subscribe(binding.Subject)));
case BindingMode.OneTime:
var source = binding.Subject ?? binding.Observable;
if (source != null)
{
// Perf: Avoid allocating closure in the outer scope.
var targetCopy = target;
var propertyCopy = property;
var bindingCopy = binding;
return(source
.Where(x => BindingNotification.ExtractValue(x) != AvaloniaProperty.UnsetValue)
.Take(1)
.Subscribe(x => targetCopy.SetValue(
propertyCopy,
BindingNotification.ExtractValue(x),
bindingCopy.Priority)));
}
else
{
target.SetValue(property, binding.Value, binding.Priority);
return(Disposable.Empty);
}
case BindingMode.OneWayToSource:
{
if (binding.Observable is null)
{
throw new InvalidOperationException("InstancedBinding does not contain an observable.");
}
if (binding.Subject is null)
{
throw new InvalidOperationException("InstancedBinding does not contain a subject.");
}
// Perf: Avoid allocating closure in the outer scope.
var bindingCopy = binding;
return(Observable.CombineLatest(
binding.Observable,
target.GetObservable(property),
(_, v) => v)
.Subscribe(x => bindingCopy.Subject.OnNext(x)));
}
default:
throw new ArgumentException("Invalid binding mode.");
}
}
/// <summary>
/// Applies a binding subject to a property on an instance.
/// </summary>
/// <param name="target">The target instance.</param>
/// <param name="property">The target property.</param>
/// <param name="subject">The binding subject.</param>
internal void Bind(IAvaloniaObject target, AvaloniaProperty property, ISubject<object> subject)
{
var mode = Mode == BindingMode.Default ?
property.GetMetadata(target.GetType()).DefaultBindingMode : Mode;
switch (mode)
{
case BindingMode.Default:
case BindingMode.OneWay:
target.Bind(property, subject, Priority);
break;
case BindingMode.TwoWay:
throw new NotSupportedException("TwoWay MultiBinding not currently supported.");
case BindingMode.OneTime:
target.GetObservable(Control.DataContextProperty).Subscribe(dataContext =>
{
subject.Take(1).Subscribe(x => target.SetValue(property, x, Priority));
});
break;
case BindingMode.OneWayToSource:
target.GetObservable(property).Subscribe(subject);
break;
}
}
private ExpressionObserver CreateTemplatedParentObserver(
IAvaloniaObject target,
string path)
{
Contract.Requires<ArgumentNullException>(target != null);
var update = target.GetObservable(Control.TemplatedParentProperty)
.Skip(1)
.Select(_ => Unit.Default);
var result = new ExpressionObserver(
() => target.GetValue(Control.TemplatedParentProperty),
path,
update);
return result;
}
private ExpressionObserver CreateDataContexObserver(
IAvaloniaObject target,
string path,
bool targetIsDataContext,
object anchor)
{
Contract.Requires<ArgumentNullException>(target != null);
if (!(target is IControl))
{
target = anchor as IControl;
if (target == null)
{
throw new InvalidOperationException("Cannot find a DataContext to bind to.");
}
}
if (!targetIsDataContext)
{
var update = target.GetObservable(Control.DataContextProperty)
.Skip(1)
.Select(_ => Unit.Default);
var result = new ExpressionObserver(
() => target.GetValue(Control.DataContextProperty),
path,
update,
EnableValidation);
return result;
}
else
{
return new ExpressionObserver(
target.GetObservable(Visual.VisualParentProperty)
.OfType<IAvaloniaObject>()
.Select(x => x.GetObservable(Control.DataContextProperty))
.Switch(),
path,
EnableValidation);
}
}
private IObservable<object> GetParentDataContext(IAvaloniaObject target)
{
// The DataContext is based on the visual parent and not the logical parent: this may
// seem unintuitive considering the fact that property inheritance works on the logical
// tree, but consider a ContentControl with a ContentPresenter. The ContentControl's
// Content property is bound to a value which becomes the ContentPresenter's
// DataContext - it is from this that the child hosted by the ContentPresenter needs to
// inherit its DataContext.
return target.GetObservable(Visual.VisualParentProperty)
.Select(x =>
{
return (x as IAvaloniaObject)?.GetObservable(Control.DataContextProperty) ??
Observable.Return((object)null);
}).Switch();
}
