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using System;
using System.ComponentModel;
using AppKit;
using RectangleF = CoreGraphics.CGRect;
using ObjCRuntime;
using Foundation;
// ReSharper disable UnusedMember.Local
// ReSharper disable UnusedParameter.Local
namespace Xamarin.Forms.Platform.MacOS
{
public class ScrollViewRenderer : NSScrollView, IVisualElementRenderer
{
EventTracker _events;
VisualElementTracker _tracker;
ScrollToRequestedEventArgs _requestedScroll;
IVisualElementRenderer _contentRenderer;
public ScrollViewRenderer() : base(RectangleF.Empty)
{
DrawsBackground = false;
ContentView.PostsBoundsChangedNotifications = true;
NSNotificationCenter.DefaultCenter.AddObserver(this, new Selector(nameof(UpdateScrollPosition)),
BoundsChangedNotification, ContentView);
}
IScrollViewController Controller => Element as IScrollViewController;
public VisualElement Element { get; private set; }
public event EventHandler<VisualElementChangedEventArgs> ElementChanged;
public SizeRequest GetDesiredSize(double widthConstraint, double heightConstraint)
{
return NativeView.GetSizeRequest(widthConstraint, heightConstraint, 44, 44);
}
public NSView NativeView => this;
public void SetElement(VisualElement element)
{
_requestedScroll = null;
var oldElement = Element;
Element = element;
if (oldElement != null)
{
oldElement.PropertyChanged -= HandlePropertyChanged;
((IScrollViewController)oldElement).ScrollToRequested -= OnScrollToRequested;
}
if (element != null)
{
element.PropertyChanged += HandlePropertyChanged;
((IScrollViewController)element).ScrollToRequested += OnScrollToRequested;
if (_tracker == null)
{
PackContent();
_events = new EventTracker(this);
_events.LoadEvents(this);
_tracker = new VisualElementTracker(this);
_tracker.NativeControlUpdated += OnNativeControlUpdated;
}
UpdateContentSize();
UpdateBackgroundColor();
OnElementChanged(new VisualElementChangedEventArgs(oldElement, element));
}
}
public void SetElementSize(Size size)
{
Xamarin.Forms.Layout.LayoutChildIntoBoundingRegion(Element,
new Rectangle(Element.X, Element.Y, size.Width, size.Height));
}
public NSViewController ViewController => null;
public override void Layout()
{
base.Layout();
LayoutSubviews();
}
protected override void Dispose(bool disposing)
{
if (disposing)
{
if (_tracker == null)
return;
SetElement(null);
_tracker.NativeControlUpdated -= OnNativeControlUpdated;
_tracker.Dispose();
_tracker = null;
_events.Dispose();
_events = null;
ClearContentRenderer();
//NSNotificationCenter.DefaultCenter.RemoveObserver(this, BoundsChangedNotification);
}
base.Dispose(disposing);
}
void OnElementChanged(VisualElementChangedEventArgs e)
{
ElementChanged?.Invoke(this, e);
}
void PackContent()
{
ClearContentRenderer();
if (Controller.Children.Count == 0 || !(Controller.Children[0] is VisualElement))
return;
var content = (VisualElement)Controller.Children[0];
if (Platform.GetRenderer(content) == null)
Platform.SetRenderer(content, Platform.CreateRenderer(content));
_contentRenderer = Platform.GetRenderer(content);
DocumentView = _contentRenderer.NativeView;
}
void LayoutSubviews()
{
if (_requestedScroll != null && Superview != null)
{
var request = _requestedScroll;
_requestedScroll = null;
OnScrollToRequested(this, request);
}
}
void HandlePropertyChanged(object sender, PropertyChangedEventArgs e)
{
if (e.PropertyName == ScrollView.ContentSizeProperty.PropertyName)
UpdateContentSize();
else if (e.PropertyName == VisualElement.BackgroundColorProperty.PropertyName)
UpdateBackgroundColor();
}
void HandleScrollAnimationEnded(object sender, EventArgs e)
{
Controller.SendScrollFinished();
}
void HandleScrolled(object sender, EventArgs e)
{
UpdateScrollPosition();
}
void OnNativeControlUpdated(object sender, EventArgs eventArgs)
{
UpdateContentSize();
}
void OnScrollToRequested(object sender, ScrollToRequestedEventArgs e)
{
if (Superview == null)
{
_requestedScroll = e;
return;
}
Point scrollPoint = (e.Mode == ScrollToMode.Position)
? new Point(e.ScrollX, Element.Height - e.ScrollY)
: Controller.GetScrollPositionForElement(e.Element as VisualElement, e.Position);
(DocumentView as NSView)?.ScrollPoint(scrollPoint.ToPointF());
Controller.SendScrollFinished();
}
void UpdateBackgroundColor()
{
BackgroundColor = Element.BackgroundColor.ToNSColor(Color.Transparent);
}
void UpdateContentSize()
{
if (_contentRenderer == null)
return;
var contentSize = ((ScrollView)Element).ContentSize.ToSizeF();
if (!contentSize.IsEmpty)
_contentRenderer.NativeView.Frame = new RectangleF(0, Element.Height - contentSize.Height, contentSize.Width,
contentSize.Height);
}
[Export(nameof(UpdateScrollPosition))]
void UpdateScrollPosition()
{
var convertedPoint = (DocumentView as NSView)?.ConvertPointFromView(ContentView.Bounds.Location, ContentView);
if (convertedPoint.HasValue)
Controller.SetScrolledPosition(Math.Max(0, convertedPoint.Value.X), Math.Max(0, convertedPoint.Value.Y));
}
void ClearContentRenderer()
{
_contentRenderer?.NativeView?.RemoveFromSuperview();
_contentRenderer?.Dispose();
_contentRenderer = null;
}
}
}
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