227 строки
6.6 KiB
C#
227 строки
6.6 KiB
C#
using System;
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using System.Collections;
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using System.Collections.Generic;
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using System.Collections.ObjectModel;
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using System.Collections.Specialized;
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using System.ComponentModel;
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using System.Runtime.CompilerServices;
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using Xamarin.Forms.Internals;
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using Xamarin.Forms.Platform;
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namespace Xamarin.Forms
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{
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[RenderWith(typeof(_PickerRenderer))]
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public class Picker : View, ITextElement, IElementConfiguration<Picker>
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{
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public static readonly BindableProperty TextColorProperty = TextElement.TextColorProperty;
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public static readonly BindableProperty TitleProperty =
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BindableProperty.Create(nameof(Title), typeof(string), typeof(Picker), default(string));
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public static readonly BindableProperty SelectedIndexProperty =
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BindableProperty.Create(nameof(SelectedIndex), typeof(int), typeof(Picker), -1, BindingMode.TwoWay,
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propertyChanged: OnSelectedIndexChanged, coerceValue: CoerceSelectedIndex);
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public static readonly BindableProperty ItemsSourceProperty =
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BindableProperty.Create(nameof(ItemsSource), typeof(IList), typeof(Picker), default(IList),
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propertyChanged: OnItemsSourceChanged);
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public static readonly BindableProperty SelectedItemProperty =
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BindableProperty.Create(nameof(SelectedItem), typeof(object), typeof(Picker), null, BindingMode.TwoWay,
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propertyChanged: OnSelectedItemChanged);
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readonly Lazy<PlatformConfigurationRegistry<Picker>> _platformConfigurationRegistry;
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public Picker()
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{
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((INotifyCollectionChanged)Items).CollectionChanged += OnItemsCollectionChanged;
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_platformConfigurationRegistry = new Lazy<PlatformConfigurationRegistry<Picker>>(() => new PlatformConfigurationRegistry<Picker>(this));
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}
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public IList<string> Items { get; } = new LockableObservableListWrapper();
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public IList ItemsSource
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{
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get { return (IList)GetValue(ItemsSourceProperty); }
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set { SetValue(ItemsSourceProperty, value); }
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}
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public int SelectedIndex
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{
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get { return (int)GetValue(SelectedIndexProperty); }
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set { SetValue(SelectedIndexProperty, value); }
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}
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public object SelectedItem
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{
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get { return GetValue(SelectedItemProperty); }
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set { SetValue(SelectedItemProperty, value); }
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}
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public Color TextColor {
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get { return (Color)GetValue(TextElement.TextColorProperty); }
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set { SetValue(TextElement.TextColorProperty, value); }
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}
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public string Title {
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get { return (string)GetValue(TitleProperty); }
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set { SetValue(TitleProperty, value); }
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}
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BindingBase _itemDisplayBinding;
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public BindingBase ItemDisplayBinding {
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get { return _itemDisplayBinding; }
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set {
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if (_itemDisplayBinding == value)
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return;
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OnPropertyChanging();
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var oldValue = value;
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_itemDisplayBinding = value;
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OnItemDisplayBindingChanged(oldValue, _itemDisplayBinding);
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OnPropertyChanged();
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}
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}
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public event EventHandler SelectedIndexChanged;
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static readonly BindableProperty s_displayProperty =
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BindableProperty.Create("Display", typeof(string), typeof(Picker), default(string));
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string GetDisplayMember(object item)
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{
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if (ItemDisplayBinding == null)
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return item.ToString();
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ItemDisplayBinding.Apply(item, this, s_displayProperty);
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ItemDisplayBinding.Unapply();
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return (string)GetValue(s_displayProperty);
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}
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static object CoerceSelectedIndex(BindableObject bindable, object value)
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{
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var picker = (Picker)bindable;
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return picker.Items == null ? -1 : ((int)value).Clamp(-1, picker.Items.Count - 1);
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}
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void OnItemDisplayBindingChanged(BindingBase oldValue, BindingBase newValue)
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{
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ResetItems();
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}
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void OnItemsCollectionChanged(object sender, NotifyCollectionChangedEventArgs e)
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{
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SelectedIndex = SelectedIndex.Clamp(-1, Items.Count - 1);
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UpdateSelectedItem();
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}
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static void OnItemsSourceChanged(BindableObject bindable, object oldValue, object newValue)
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{
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((Picker)bindable).OnItemsSourceChanged((IList)oldValue, (IList)newValue);
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}
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void OnItemsSourceChanged(IList oldValue, IList newValue)
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{
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var oldObservable = oldValue as INotifyCollectionChanged;
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if (oldObservable != null)
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oldObservable.CollectionChanged -= CollectionChanged;
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var newObservable = newValue as INotifyCollectionChanged;
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if (newObservable != null) {
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newObservable.CollectionChanged += CollectionChanged;
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}
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if (newValue != null) {
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((LockableObservableListWrapper)Items).IsLocked = true;
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ResetItems();
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} else {
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((LockableObservableListWrapper)Items).InternalClear();
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((LockableObservableListWrapper)Items).IsLocked = false;
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}
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}
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void CollectionChanged(object sender, NotifyCollectionChangedEventArgs e)
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{
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switch (e.Action) {
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case NotifyCollectionChangedAction.Add:
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AddItems(e);
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break;
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case NotifyCollectionChangedAction.Remove:
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RemoveItems(e);
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break;
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default: //Move, Replace, Reset
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ResetItems();
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break;
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}
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}
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void AddItems(NotifyCollectionChangedEventArgs e)
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{
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int index = e.NewStartingIndex < 0 ? Items.Count : e.NewStartingIndex;
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foreach (object newItem in e.NewItems)
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((LockableObservableListWrapper)Items).InternalInsert(index++, GetDisplayMember(newItem));
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}
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void RemoveItems(NotifyCollectionChangedEventArgs e)
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{
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int index = e.OldStartingIndex < Items.Count ? e.OldStartingIndex : Items.Count;
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foreach (object _ in e.OldItems)
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((LockableObservableListWrapper)Items).InternalRemoveAt(index--);
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}
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void ResetItems()
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{
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if (ItemsSource == null)
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return;
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((LockableObservableListWrapper)Items).InternalClear();
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foreach (object item in ItemsSource)
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((LockableObservableListWrapper)Items).InternalAdd(GetDisplayMember(item));
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UpdateSelectedItem();
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}
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static void OnSelectedIndexChanged(object bindable, object oldValue, object newValue)
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{
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var picker = (Picker)bindable;
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picker.UpdateSelectedItem();
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picker.SelectedIndexChanged?.Invoke(bindable, EventArgs.Empty);
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}
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static void OnSelectedItemChanged(BindableObject bindable, object oldValue, object newValue)
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{
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var picker = (Picker)bindable;
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picker.UpdateSelectedIndex(newValue);
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}
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void UpdateSelectedIndex(object selectedItem)
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{
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if (ItemsSource != null) {
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SelectedIndex = ItemsSource.IndexOf(selectedItem);
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return;
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}
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SelectedIndex = Items.IndexOf(selectedItem);
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}
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void UpdateSelectedItem()
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{
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if (SelectedIndex == -1) {
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SelectedItem = null;
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return;
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}
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if (ItemsSource != null) {
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SelectedItem = ItemsSource [SelectedIndex];
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return;
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}
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SelectedItem = Items [SelectedIndex];
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}
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public IPlatformElementConfiguration<T, Picker> On<T>() where T : IConfigPlatform
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{
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return _platformConfigurationRegistry.Value.On<T>();
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}
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void ITextElement.OnTextColorPropertyChanged(Color oldValue, Color newValue)
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{
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}
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}
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} |