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VisualElement.Impl.cs
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/
VisualElement.Impl.cs
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#nullable enable
using System;
using System.ComponentModel;
using Microsoft.Maui.Graphics;
using Microsoft.Maui.Layouts;
namespace Microsoft.Maui.Controls
{
/// <include file="../../../../docs/Microsoft.Maui.Controls/VisualElement.xml" path="Type[@FullName='Microsoft.Maui.Controls.VisualElement']/Docs" />
public partial class VisualElement : IView
{
Semantics _semantics;
bool _isLoadedFired;
EventHandler? _loaded;
EventHandler? _unloaded;
bool _watchingPlatformLoaded;
Rect _frame = new Rect(0, 0, -1, -1);
/// <include file="../../../../docs/Microsoft.Maui.Controls/VisualElement.xml" path="//Member[@MemberName='Frame']/Docs" />
public Rect Frame
{
get => _frame;
set
{
if (_frame == value)
return;
UpdateBoundsComponents(value);
}
}
/// <include file="../../../../docs/Microsoft.Maui.Controls/VisualElement.xml" path="//Member[@MemberName='Handler']/Docs" />
new public IViewHandler? Handler
{
get => (IViewHandler?)base.Handler;
set => base.Handler = value;
}
private protected override void OnHandlerChangedCore()
{
base.OnHandlerChangedCore();
IsPlatformEnabled = Handler != null;
UpdatePlatformUnloadedLoadedWiring(Window);
}
Paint? IView.Background
{
get
{
if (!Brush.IsNullOrEmpty(Background))
return Background;
if (BackgroundColor.IsNotDefault())
return new SolidColorBrush(BackgroundColor);
return null;
}
}
IShape IView.Clip => Clip;
IShadow IView.Shadow => Shadow;
/// <include file="../../../../docs/Microsoft.Maui.Controls/VisualElement.xml" path="//Member[@MemberName='ShadowProperty']/Docs" />
public static readonly BindableProperty ShadowProperty =
BindableProperty.Create(nameof(Shadow), typeof(Shadow), typeof(VisualElement), defaultValue: null,
propertyChanging: (bindable, oldvalue, newvalue) =>
{
if (oldvalue != null)
(bindable as VisualElement)?.StopNotifyingShadowChanges();
},
propertyChanged: (bindable, oldvalue, newvalue) =>
{
if (newvalue != null)
(bindable as VisualElement)?.NotifyShadowChanges();
});
/// <include file="../../../../docs/Microsoft.Maui.Controls/VisualElement.xml" path="//Member[@MemberName='Shadow']/Docs" />
public Shadow Shadow
{
get { return (Shadow)GetValue(ShadowProperty); }
set { SetValue(ShadowProperty, value); }
}
internal static readonly BindableProperty ZIndexProperty =
BindableProperty.Create(nameof(ZIndex), typeof(int), typeof(View), default(int),
propertyChanged: ZIndexPropertyChanged);
static void ZIndexPropertyChanged(BindableObject bindable, object oldValue, object newValue)
{
if (bindable is IView view)
{
view.Handler?.Invoke(nameof(IView.ZIndex));
}
}
/// <include file="../../../../docs/Microsoft.Maui.Controls/VisualElement.xml" path="//Member[@MemberName='ZIndex']/Docs" />
public int ZIndex
{
get { return (int)GetValue(ZIndexProperty); }
set { SetValue(ZIndexProperty, value); }
}
/// <include file="../../../../docs/Microsoft.Maui.Controls/VisualElement.xml" path="//Member[@MemberName='DesiredSize']/Docs" />
public Size DesiredSize { get; protected set; }
/// <include file="../../../../docs/Microsoft.Maui.Controls/VisualElement.xml" path="//Member[@MemberName='Arrange']/Docs" />
public void Arrange(Rect bounds)
{
Layout(bounds);
}
Size IView.Arrange(Rect bounds)
{
return ArrangeOverride(bounds);
}
// ArrangeOverride provides a way to allow subclasses (e.g., ScrollView) to override Arrange even though
// the interface has to be explicitly implemented to avoid conflict with the old Arrange method
protected virtual Size ArrangeOverride(Rect bounds)
{
Frame = this.ComputeFrame(bounds);
Handler?.PlatformArrange(Frame);
return Frame.Size;
}
/// <include file="../../../../docs/Microsoft.Maui.Controls/VisualElement.xml" path="//Member[@MemberName='Layout']/Docs" />
public void Layout(Rect bounds)
{
Bounds = bounds;
}
void IView.InvalidateMeasure()
{
InvalidateMeasureOverride();
}
// InvalidateMeasureOverride provides a way to allow subclasses (e.g., Layout) to override InvalidateMeasure even though
// the interface has to be explicitly implemented to avoid conflict with the VisualElement.InvalidateMeasure method
protected virtual void InvalidateMeasureOverride() => Handler?.Invoke(nameof(IView.InvalidateMeasure));
void IView.InvalidateArrange()
{
}
Size IView.Measure(double widthConstraint, double heightConstraint)
{
return MeasureOverride(widthConstraint, heightConstraint);
}
// MeasureOverride provides a way to allow subclasses (e.g., Layout) to override Measure even though
// the interface has to be explicitly implemented to avoid conflict with the old Measure method
protected virtual Size MeasureOverride(double widthConstraint, double heightConstraint)
{
DesiredSize = this.ComputeDesiredSize(widthConstraint, heightConstraint);
return DesiredSize;
}
bool IView.IsFocused
{
get => (bool)GetValue(IsFocusedProperty);
set => SetValueCore(IsFocusedPropertyKey, value);
}
FlowDirection IView.FlowDirection => FlowDirection;
Primitives.LayoutAlignment IView.HorizontalLayoutAlignment => default;
Primitives.LayoutAlignment IView.VerticalLayoutAlignment => default;
Visibility IView.Visibility => IsVisible.ToVisibility();
Semantics IView.Semantics
{
get => _semantics;
}
// We don't want to initialize Semantics until someone explicitly
// wants to modify some aspect of the semantics class
internal Semantics SetupSemantics() =>
_semantics ??= new Semantics();
static void ValidatePositive(double value, string name)
{
if (value < 0)
{
throw new InvalidOperationException($"{name} cannot be less than zero.");
}
}
double IView.Width
{
get
{
if (!IsSet(WidthRequestProperty))
{
return Primitives.Dimension.Unset;
}
// Access once up front to avoid multiple GetValue calls
var value = WidthRequest;
if (value == -1)
{
return Primitives.Dimension.Unset;
}
ValidatePositive(value, nameof(IView.Width));
return value;
}
}
double IView.Height
{
get
{
if (!IsSet(HeightRequestProperty))
{
return Primitives.Dimension.Unset;
}
// Access once up front to avoid multiple GetValue calls
var value = HeightRequest;
if (value == -1)
{
return Primitives.Dimension.Unset;
}
ValidatePositive(value, nameof(IView.Height));
return value;
}
}
double IView.MinimumWidth
{
get
{
if (!IsSet(MinimumWidthRequestProperty))
{
return Primitives.Dimension.Unset;
}
// Access once up front to avoid multiple GetValue calls
var value = MinimumWidthRequest;
ValidatePositive(value, nameof(IView.MinimumWidth));
return value;
}
}
double IView.MinimumHeight
{
get
{
if (!IsSet(MinimumHeightRequestProperty))
{
return Primitives.Dimension.Unset;
}
// Access once up front to avoid multiple GetValue calls
var value = MinimumHeightRequest;
ValidatePositive(value, nameof(IView.MinimumHeight));
return value;
}
}
double IView.MaximumWidth
{
get
{
// Access once up front to avoid multiple GetValue calls
var value = MaximumWidthRequest;
ValidatePositive(value, nameof(IView.MaximumWidth));
return value;
}
}
double IView.MaximumHeight
{
get
{
// Access once up front to avoid multiple GetValue calls
var value = MaximumHeightRequest;
ValidatePositive(value, nameof(IView.MaximumHeight));
return value;
}
}
Thickness IView.Margin => Thickness.Zero;
IElementHandler? Maui.IElement.Handler
{
get => base.Handler;
set
{
if (value != null && value is not IViewHandler)
throw new InvalidOperationException("Handler must be of type IViewHandler");
base.Handler = value;
}
}
void NotifyShadowChanges()
{
if (Shadow != null)
{
Shadow.Parent = this;
Shadow.PropertyChanged += OnShadowChanged;
}
}
void StopNotifyingShadowChanges()
{
if (Shadow != null)
{
Shadow.Parent = null;
Shadow.PropertyChanged -= OnShadowChanged;
}
}
void OnShadowChanged(object? sender, PropertyChangedEventArgs e)
{
OnPropertyChanged(nameof(Shadow));
}
void PropagateBindingContextToShadow()
{
if (Shadow != null)
SetInheritedBindingContext(Shadow, BindingContext);
}
public bool IsLoaded
{
get
{
#if PLATFORM
bool isLoaded = (Handler as IPlatformViewHandler)?.PlatformView?.IsLoaded() == true;
#else
bool isLoaded = Window != null;
#endif
return isLoaded;
}
}
public event EventHandler? Loaded
{
add
{
_loaded += value;
UpdatePlatformUnloadedLoadedWiring(Window);
if (_isLoadedFired)
_loaded?.Invoke(this, EventArgs.Empty);
}
remove
{
_loaded -= value;
UpdatePlatformUnloadedLoadedWiring(Window);
}
}
public event EventHandler? Unloaded
{
add
{
_unloaded += value;
UpdatePlatformUnloadedLoadedWiring(Window);
}
remove
{
_unloaded -= value;
UpdatePlatformUnloadedLoadedWiring(Window);
}
}
void OnLoadedCore()
{
if (_isLoadedFired)
return;
_isLoadedFired = true;
_loaded?.Invoke(this, EventArgs.Empty);
}
void OnUnloadedCore()
{
if (!_isLoadedFired)
return;
_isLoadedFired = false;
_unloaded?.Invoke(this, EventArgs.Empty);
}
static void OnWindowChanged(BindableObject bindable, object? oldValue, object? newValue)
{
if (bindable is not VisualElement visualElement)
return;
if (visualElement._watchingPlatformLoaded && oldValue is Window oldWindow)
oldWindow.HandlerChanged -= visualElement.OnWindowHandlerChanged;
visualElement.UpdatePlatformUnloadedLoadedWiring(newValue as Window);
}
void OnWindowHandlerChanged(object? sender, EventArgs e)
{
UpdatePlatformUnloadedLoadedWiring(Window);
}
// We only want to wire up to platform loaded events
// if the user is watching for them. Otherwise
// this will get wired up for every single VE that's on
// the screen
void UpdatePlatformUnloadedLoadedWiring(Window? window)
{
// If I'm not attached to a window and I haven't started watching any platform events
// then it's not useful to wire anything up. We will just wait until
// This VE gets connected to the xplat Window before wiring up any events
if (!_watchingPlatformLoaded && window == null)
return;
if (_unloaded == null && _loaded == null)
{
if (window is not null)
window.HandlerChanged -= OnWindowHandlerChanged;
#if PLATFORM
_loadedUnloadedToken?.Dispose();
_loadedUnloadedToken = null;
#endif
_watchingPlatformLoaded = false;
return;
}
if (!_watchingPlatformLoaded)
{
if (window is not null)
window.HandlerChanged += OnWindowHandlerChanged;
_watchingPlatformLoaded = true;
}
HandlePlatformUnloadedLoaded();
}
partial void HandlePlatformUnloadedLoaded();
internal IView? ParentView => ((this as IView)?.Parent as IView);
}
}