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Control.cs
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Control.cs
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// Copyright (c) The Avalonia Project. All rights reserved.
// Licensed under the MIT license. See licence.md file in the project root for full license information.
using System;
using System.Collections.Generic;
using System.Collections.Specialized;
using System.Linq;
using System.Reactive;
using System.Reactive.Linq;
using System.Reactive.Subjects;
using Avalonia.Collections;
using Avalonia.Controls.Primitives;
using Avalonia.Controls.Templates;
using Avalonia.Data;
using Avalonia.Diagnostics;
using Avalonia.Input;
using Avalonia.Interactivity;
using Avalonia.Logging;
using Avalonia.LogicalTree;
using Avalonia.Styling;
namespace Avalonia.Controls
{
/// <summary>
/// Base class for Avalonia controls.
/// </summary>
/// <remarks>
/// The control class extends <see cref="InputElement"/> and adds the following features:
///
/// - An inherited <see cref="DataContext"/>.
/// - A <see cref="Tag"/> property to allow user-defined data to be attached to the control.
/// - A collection of class strings for custom styling.
/// - Implements <see cref="IStyleable"/> to allow styling to work on the control.
/// - Implements <see cref="ILogical"/> to form part of a logical tree.
/// </remarks>
public class Control : InputElement, IControl, INamed, ISetInheritanceParent, ISetLogicalParent, ISupportInitialize
{
/// <summary>
/// Defines the <see cref="DataContext"/> property.
/// </summary>
public static readonly StyledProperty<object> DataContextProperty =
AvaloniaProperty.Register<Control, object>(
nameof(DataContext),
inherits: true,
notifying: DataContextNotifying);
/// <summary>
/// Defines the <see cref="FocusAdorner"/> property.
/// </summary>
public static readonly StyledProperty<ITemplate<IControl>> FocusAdornerProperty =
AvaloniaProperty.Register<Control, ITemplate<IControl>>(nameof(FocusAdorner));
/// <summary>
/// Defines the <see cref="Name"/> property.
/// </summary>
public static readonly DirectProperty<Control, string> NameProperty =
AvaloniaProperty.RegisterDirect<Control, string>(nameof(Name), o => o.Name, (o, v) => o.Name = v);
/// <summary>
/// Defines the <see cref="Parent"/> property.
/// </summary>
public static readonly DirectProperty<Control, IControl> ParentProperty =
AvaloniaProperty.RegisterDirect<Control, IControl>(nameof(Parent), o => o.Parent);
/// <summary>
/// Defines the <see cref="Tag"/> property.
/// </summary>
public static readonly StyledProperty<object> TagProperty =
AvaloniaProperty.Register<Control, object>(nameof(Tag));
/// <summary>
/// Defines the <see cref="TemplatedParent"/> property.
/// </summary>
public static readonly StyledProperty<ITemplatedControl> TemplatedParentProperty =
AvaloniaProperty.Register<Control, ITemplatedControl>(nameof(TemplatedParent), inherits: true);
/// <summary>
/// Defines the <see cref="ContextMenu"/> property.
/// </summary>
public static readonly StyledProperty<ContextMenu> ContextMenuProperty =
AvaloniaProperty.Register<Control, ContextMenu>(nameof(ContextMenu));
/// <summary>
/// Event raised when an element wishes to be scrolled into view.
/// </summary>
public static readonly RoutedEvent<RequestBringIntoViewEventArgs> RequestBringIntoViewEvent =
RoutedEvent.Register<Control, RequestBringIntoViewEventArgs>("RequestBringIntoView", RoutingStrategies.Bubble);
private int _initCount;
private string _name;
private IControl _parent;
private readonly Classes _classes = new Classes();
private DataTemplates _dataTemplates;
private IControl _focusAdorner;
private bool _isAttachedToLogicalTree;
private IAvaloniaList<ILogical> _logicalChildren;
private INameScope _nameScope;
private Styles _styles;
private bool _styled;
private Subject<IStyleable> _styleDetach = new Subject<IStyleable>();
/// <summary>
/// Initializes static members of the <see cref="Control"/> class.
/// </summary>
static Control()
{
AffectsMeasure(IsVisibleProperty);
PseudoClass(IsEnabledCoreProperty, x => !x, ":disabled");
PseudoClass(IsFocusedProperty, ":focus");
PseudoClass(IsPointerOverProperty, ":pointerover");
PseudoClass(ValidationStatusProperty, status => !status.IsValid, ":invalid");
}
/// <summary>
/// Initializes a new instance of the <see cref="Control"/> class.
/// </summary>
public Control()
{
_nameScope = this as INameScope;
}
/// <summary>
/// Raised when the control is attached to a rooted logical tree.
/// </summary>
public event EventHandler<LogicalTreeAttachmentEventArgs> AttachedToLogicalTree;
/// <summary>
/// Raised when the control is detached from a rooted logical tree.
/// </summary>
public event EventHandler<LogicalTreeAttachmentEventArgs> DetachedFromLogicalTree;
/// <summary>
/// Occurs when the <see cref="DataContext"/> property changes.
/// </summary>
/// <remarks>
/// This event will be raised when the <see cref="DataContext"/> property has changed and
/// all subscribers to that change have been notified.
/// </remarks>
public event EventHandler DataContextChanged;
/// <summary>
/// Occurs when the control has finished initialization.
/// </summary>
/// <remarks>
/// The Initialized event indicates that all property values on the control have been set.
/// When loading the control from markup, it occurs when
/// <see cref="ISupportInitialize.EndInit"/> is called *and* the control
/// is attached to a rooted logical tree. When the control is created by code and
/// <see cref="ISupportInitialize"/> is not used, it is called when the control is attached
/// to the visual tree.
/// </remarks>
public event EventHandler Initialized;
/// <summary>
/// Gets or sets the name of the control.
/// </summary>
/// <remarks>
/// An element's name is used to uniquely identify a control within the control's name
/// scope. Once the element is added to a logical tree, its name cannot be changed.
/// </remarks>
public string Name
{
get
{
return _name;
}
set
{
if (value.Trim() == string.Empty)
{
throw new InvalidOperationException("Cannot set Name to empty string.");
}
if (_styled)
{
throw new InvalidOperationException("Cannot set Name : control already styled.");
}
_name = value;
}
}
/// <summary>
/// Gets or sets the control's classes.
/// </summary>
/// <remarks>
/// <para>
/// Classes can be used to apply user-defined styling to controls, or to allow controls
/// that share a common purpose to be easily selected.
/// </para>
/// <para>
/// Even though this property can be set, the setter is only intended for use in object
/// initializers. Assigning to this property does not change the underlying collection,
/// it simply clears the existing collection and addds the contents of the assigned
/// collection.
/// </para>
/// </remarks>
public Classes Classes
{
get
{
return _classes;
}
set
{
if (_classes != value)
{
_classes.Replace(value);
}
}
}
/// <summary>
/// Gets or sets the control's data context.
/// </summary>
/// <remarks>
/// The data context is an inherited property that specifies the default object that will
/// be used for data binding.
/// </remarks>
public object DataContext
{
get { return GetValue(DataContextProperty); }
set { SetValue(DataContextProperty, value); }
}
/// <summary>
/// Gets or sets the control's focus adorner.
/// </summary>
public ITemplate<IControl> FocusAdorner
{
get { return GetValue(FocusAdornerProperty); }
set { SetValue(FocusAdornerProperty, value); }
}
/// <summary>
/// Gets or sets the data templates for the control.
/// </summary>
/// <remarks>
/// Each control may define data templates which are applied to the control itself and its
/// children.
/// </remarks>
public DataTemplates DataTemplates
{
get { return _dataTemplates ?? (_dataTemplates = new DataTemplates()); }
set { _dataTemplates = value; }
}
/// <summary>
/// Gets a value that indicates whether the element has finished initialization.
/// </summary>
/// <remarks>
/// For more information about when IsInitialized is set, see the <see cref="Initialized"/>
/// event.
/// </remarks>
public bool IsInitialized { get; private set; }
/// <summary>
/// Gets or sets the styles for the control.
/// </summary>
/// <remarks>
/// Styles for the entire application are added to the Application.Styles collection, but
/// each control may in addition define its own styles which are applied to the control
/// itself and its children.
/// </remarks>
public Styles Styles
{
get { return _styles ?? (_styles = new Styles()); }
set { _styles = value; }
}
/// <summary>
/// Gets the control's logical parent.
/// </summary>
public IControl Parent => _parent;
/// <summary>
/// Gets or sets a context menu to the control.
/// </summary>
public ContextMenu ContextMenu
{
get { return GetValue(ContextMenuProperty); }
set { SetValue(ContextMenuProperty, value); }
}
/// <summary>
/// Gets or sets a user-defined object attached to the control.
/// </summary>
public object Tag
{
get { return GetValue(TagProperty); }
set { SetValue(TagProperty, value); }
}
/// <summary>
/// Gets the control whose lookless template this control is part of.
/// </summary>
public ITemplatedControl TemplatedParent
{
get { return GetValue(TemplatedParentProperty); }
internal set { SetValue(TemplatedParentProperty, value); }
}
/// <summary>
/// Gets a value indicating whether the element is attached to a rooted logical tree.
/// </summary>
bool ILogical.IsAttachedToLogicalTree => _isAttachedToLogicalTree;
/// <summary>
/// Gets the control's logical parent.
/// </summary>
ILogical ILogical.LogicalParent => Parent;
/// <summary>
/// Gets the control's logical children.
/// </summary>
IAvaloniaReadOnlyList<ILogical> ILogical.LogicalChildren => LogicalChildren;
/// <inheritdoc/>
IAvaloniaReadOnlyList<string> IStyleable.Classes => Classes;
/// <summary>
/// Gets the type by which the control is styled.
/// </summary>
/// <remarks>
/// Usually controls are styled by their own type, but there are instances where you want
/// a control to be styled by its base type, e.g. creating SpecialButton that
/// derives from Button and adds extra functionality but is still styled as a regular
/// Button.
/// </remarks>
Type IStyleable.StyleKey => GetType();
/// <inheritdoc/>
IObservable<IStyleable> IStyleable.StyleDetach => _styleDetach;
/// <inheritdoc/>
IStyleHost IStyleHost.StylingParent => (IStyleHost)InheritanceParent;
/// <inheritdoc/>
public virtual void BeginInit()
{
++_initCount;
}
/// <inheritdoc/>
public virtual void EndInit()
{
if (_initCount == 0)
{
throw new InvalidOperationException("BeginInit was not called.");
}
if (--_initCount == 0 && _isAttachedToLogicalTree)
{
if (!_styled)
{
RegisterWithNameScope();
ApplyStyling();
_styled = true;
}
if (!IsInitialized)
{
IsInitialized = true;
Initialized?.Invoke(this, EventArgs.Empty);
}
}
}
/// <inheritdoc/>
void ILogical.NotifyDetachedFromLogicalTree(LogicalTreeAttachmentEventArgs e)
{
this.OnDetachedFromLogicalTreeCore(e);
}
/// <summary>
/// Gets the control's logical children.
/// </summary>
protected IAvaloniaList<ILogical> LogicalChildren
{
get
{
if (_logicalChildren == null)
{
var list = new AvaloniaList<ILogical>();
list.ResetBehavior = ResetBehavior.Remove;
list.Validate = ValidateLogicalChild;
list.CollectionChanged += LogicalChildrenCollectionChanged;
_logicalChildren = list;
}
return _logicalChildren;
}
}
/// <summary>
/// Gets the <see cref="Classes"/> collection in a form that allows adding and removing
/// pseudoclasses.
/// </summary>
protected IPseudoClasses PseudoClasses => Classes;
/// <inheritdoc/>
protected override void DataValidationChanged(AvaloniaProperty property, IValidationStatus status)
{
base.DataValidationChanged(property, status);
ValidationStatus.UpdateValidationStatus(status);
}
/// <summary>
/// Sets the control's logical parent.
/// </summary>
/// <param name="parent">The parent.</param>
void ISetLogicalParent.SetParent(ILogical parent)
{
var old = Parent;
if (parent != old)
{
if (old != null && parent != null)
{
throw new InvalidOperationException("The Control already has a parent.");
}
if (_isAttachedToLogicalTree)
{
var oldRoot = FindStyleRoot(old);
if (oldRoot == null)
{
throw new AvaloniaInternalException("Was attached to logical tree but cannot find root.");
}
var e = new LogicalTreeAttachmentEventArgs(oldRoot);
OnDetachedFromLogicalTreeCore(e);
}
if (InheritanceParent == null || parent == null)
{
InheritanceParent = parent as AvaloniaObject;
}
_parent = (IControl)parent;
if (_parent is IStyleRoot || _parent?.IsAttachedToLogicalTree == true)
{
var newRoot = FindStyleRoot(this);
if (newRoot == null)
{
throw new AvaloniaInternalException("Parent is atttached to logical tree but cannot find root.");
}
var e = new LogicalTreeAttachmentEventArgs(newRoot);
OnAttachedToLogicalTreeCore(e);
}
RaisePropertyChanged(ParentProperty, old, _parent, BindingPriority.LocalValue);
}
}
/// <summary>
/// Sets the control's inheritance parent.
/// </summary>
/// <param name="parent">The parent.</param>
void ISetInheritanceParent.SetParent(IAvaloniaObject parent)
{
InheritanceParent = parent;
}
/// <summary>
/// Adds a pseudo-class to be set when a property is true.
/// </summary>
/// <param name="property">The property.</param>
/// <param name="className">The pseudo-class.</param>
protected static void PseudoClass(AvaloniaProperty<bool> property, string className)
{
PseudoClass(property, x => x, className);
}
/// <summary>
/// Adds a pseudo-class to be set when a property equals a certain value.
/// </summary>
/// <typeparam name="T">The type of the property.</typeparam>
/// <param name="property">The property.</param>
/// <param name="selector">Returns a boolean value based on the property value.</param>
/// <param name="className">The pseudo-class.</param>
protected static void PseudoClass<T>(
AvaloniaProperty<T> property,
Func<T, bool> selector,
string className)
{
Contract.Requires<ArgumentNullException>(property != null);
Contract.Requires<ArgumentNullException>(selector != null);
Contract.Requires<ArgumentNullException>(className != null);
Contract.Requires<ArgumentNullException>(property != null);
if (string.IsNullOrWhiteSpace(className))
{
throw new ArgumentException("Cannot supply an empty className.");
}
property.Changed.Merge(property.Initialized)
.Where(e => e.Sender is Control)
.Subscribe(e =>
{
if (selector((T)e.NewValue))
{
((Control)e.Sender).PseudoClasses.Add(className);
}
else
{
((Control)e.Sender).PseudoClasses.Remove(className);
}
});
}
/// <summary>
/// Gets the element that recieves the focus adorner.
/// </summary>
/// <returns>The control that recieves the focus adorner.</returns>
protected virtual IControl GetTemplateFocusTarget()
{
return this;
}
/// <summary>
/// Called when the control is added to a rooted logical tree.
/// </summary>
/// <param name="e">The event args.</param>
protected virtual void OnAttachedToLogicalTree(LogicalTreeAttachmentEventArgs e)
{
AttachedToLogicalTree?.Invoke(this, e);
}
/// <summary>
/// Called when the control is removed from a rooted logical tree.
/// </summary>
/// <param name="e">The event args.</param>
protected virtual void OnDetachedFromLogicalTree(LogicalTreeAttachmentEventArgs e)
{
DetachedFromLogicalTree?.Invoke(this, e);
}
/// <inheritdoc/>
protected sealed override void OnAttachedToVisualTreeCore(VisualTreeAttachmentEventArgs e)
{
base.OnAttachedToVisualTreeCore(e);
if (!IsInitialized)
{
IsInitialized = true;
Initialized?.Invoke(this, EventArgs.Empty);
}
}
/// <inheritdoc/>
protected sealed override void OnDetachedFromVisualTreeCore(VisualTreeAttachmentEventArgs e)
{
base.OnDetachedFromVisualTreeCore(e);
}
/// <summary>
/// Called before the <see cref="DataContext"/> property changes.
/// </summary>
protected virtual void OnDataContextChanging()
{
}
/// <summary>
/// Called after the <see cref="DataContext"/> property changes.
/// </summary>
protected virtual void OnDataContextChanged()
{
DataContextChanged?.Invoke(this, EventArgs.Empty);
}
/// <inheritdoc/>
protected override void OnGotFocus(GotFocusEventArgs e)
{
base.OnGotFocus(e);
if (IsFocused &&
(e.NavigationMethod == NavigationMethod.Tab ||
e.NavigationMethod == NavigationMethod.Directional))
{
var adornerLayer = AdornerLayer.GetAdornerLayer(this);
if (adornerLayer != null)
{
if (_focusAdorner == null)
{
var template = GetValue(FocusAdornerProperty);
if (template != null)
{
_focusAdorner = template.Build();
}
}
if (_focusAdorner != null)
{
var target = (Visual)GetTemplateFocusTarget();
if (target != null)
{
AdornerLayer.SetAdornedElement((Visual)_focusAdorner, target);
adornerLayer.Children.Add(_focusAdorner);
}
}
}
}
}
/// <inheritdoc/>
protected override void OnLostFocus(RoutedEventArgs e)
{
base.OnLostFocus(e);
if (_focusAdorner != null)
{
var adornerLayer = _focusAdorner.Parent as Panel;
adornerLayer.Children.Remove(_focusAdorner);
_focusAdorner = null;
}
}
/// <summary>
/// Called when the <see cref="DataContext"/> property begins and ends being notified.
/// </summary>
/// <param name="o">The object on which the DataContext is changing.</param>
/// <param name="notifying">Whether the notifcation is beginning or ending.</param>
private static void DataContextNotifying(IAvaloniaObject o, bool notifying)
{
var control = o as Control;
if (control != null)
{
if (notifying)
{
control.OnDataContextChanging();
}
else
{
control.OnDataContextChanged();
}
}
}
private static IStyleRoot FindStyleRoot(IStyleHost e)
{
while (e != null)
{
var root = e as IStyleRoot;
if (root != null && root.StylingParent == null)
{
return root;
}
e = e.StylingParent;
}
return null;
}
private void ApplyStyling()
{
AvaloniaLocator.Current.GetService<IStyler>()?.ApplyStyles(this);
}
private void RegisterWithNameScope()
{
if (_nameScope == null)
{
_nameScope = NameScope.GetNameScope(this) ?? ((Control)Parent)?._nameScope;
}
if (Name != null)
{
_nameScope?.Register(Name, this);
}
}
private static void ValidateLogicalChild(ILogical c)
{
if (c == null)
{
throw new ArgumentException("Cannot add null to LogicalChildren.");
}
}
private void OnAttachedToLogicalTreeCore(LogicalTreeAttachmentEventArgs e)
{
// This method can be called when a control is already attached to the logical tree
// in the following scenario:
// - ListBox gets assigned Items containing ListBoxItem
// - ListBox makes ListBoxItem a logical child
// - ListBox template gets applied; making its Panel get attached to logical tree
// - That AttachedToLogicalTree signal travels down to the ListBoxItem
if (!_isAttachedToLogicalTree)
{
_isAttachedToLogicalTree = true;
if (_initCount == 0)
{
RegisterWithNameScope();
ApplyStyling();
_styled = true;
}
OnAttachedToLogicalTree(e);
}
foreach (var child in LogicalChildren.OfType<Control>())
{
child.OnAttachedToLogicalTreeCore(e);
}
}
private void OnDetachedFromLogicalTreeCore(LogicalTreeAttachmentEventArgs e)
{
if (_isAttachedToLogicalTree)
{
if (Name != null)
{
_nameScope?.Unregister(Name);
}
_isAttachedToLogicalTree = false;
_styleDetach.OnNext(this);
this.TemplatedParent = null;
OnDetachedFromLogicalTree(e);
foreach (var child in LogicalChildren.OfType<Control>())
{
child.OnDetachedFromLogicalTreeCore(e);
}
#if DEBUG
if (((INotifyCollectionChangedDebug)_classes).GetCollectionChangedSubscribers()?.Length > 0)
{
Logger.Warning(
LogArea.Control,
this,
"{Type} detached from logical tree but still has class listeners",
this.GetType());
}
#endif
}
}
private void LogicalChildrenCollectionChanged(object sender, NotifyCollectionChangedEventArgs e)
{
switch (e.Action)
{
case NotifyCollectionChangedAction.Add:
SetLogicalParent(e.NewItems.Cast<ILogical>());
break;
case NotifyCollectionChangedAction.Remove:
ClearLogicalParent(e.OldItems.Cast<ILogical>());
break;
case NotifyCollectionChangedAction.Replace:
ClearLogicalParent(e.OldItems.Cast<ILogical>());
SetLogicalParent(e.NewItems.Cast<ILogical>());
break;
case NotifyCollectionChangedAction.Reset:
throw new NotSupportedException("Reset should not be signalled on LogicalChildren collection");
}
}
private void SetLogicalParent(IEnumerable<ILogical> children)
{
foreach (var i in children)
{
if (i.LogicalParent == null)
{
((ISetLogicalParent)i).SetParent(this);
}
}
}
private void ClearLogicalParent(IEnumerable<ILogical> children)
{
foreach (var i in children)
{
if (i.LogicalParent == this)
{
((ISetLogicalParent)i).SetParent(null);
}
}
}
}
}