feat: Implement SelectionStart, SelectionLength on Skia

src/Uno.UI.Runtime.Skia.Gtk/UI/Xaml/Controls/TextBoxViewExtension.cs

@@ -297,5 +297,37 @@ public void Select(int start, int length)
 			}
 			// TODO: Handle TextView..
 		}
+
+		public int GetSelectionStart()
+		{
+			if (_currentInputWidget is Entry entry)
+			{
+				entry.GetSelectionBounds(out var start, out _);
+				return start;
+			}
+			else if (_currentInputWidget is TextView textView)
+			{
+				textView.Buffer.GetSelectionBounds(out var start, out _);
+				return start.Offset; // TODO: Confirm this implementation is correct.
+			}
+
+			return 0;
+		}
+
+		public int GetSelectionLength()
+		{
+			if (_currentInputWidget is Entry entry)
+			{
+				entry.GetSelectionBounds(out var start, out var end);
+				return end - start;
+			}
+			else if (_currentInputWidget is TextView textView)
+			{
+				textView.Buffer.GetSelectionBounds(out var start, out var end);
+				return end.Offset - start.Offset;
+			}
+
+			return 0;
+		}
 	}
 }

src/Uno.UI.Runtime.Skia.Wpf/Extensions/UI/Xaml/Controls/TextBoxViewExtension.cs

@@ -189,5 +189,9 @@ public void SetIsPassword(bool isPassword)
 		}
 
 		public void Select(int start, int length) => _currentInputWidget?.Select(start, length);
+
+		public int GetSelectionStart() => _currentInputWidget?.SelectionStart ?? 0;
+
+		public int GetSelectionLength() => _currentInputWidget?.SelectionLength ?? 0;
 	}
 }

src/Uno.UI/Generated/3.0.0.0/Windows.UI.Xaml.Controls/TextBox.cs

@@ -10,7 +10,7 @@ public  partial class TextBox
 		// Skipping already declared property TextWrapping
 		// Skipping already declared property TextAlignment
 		// Skipping already declared property Text
-		#if false || false || NET461 || false || __SKIA__ || __NETSTD_REFERENCE__ || false
+		#if false || false || NET461 || false || false || __NETSTD_REFERENCE__ || false
 		[global::Uno.NotImplemented("NET461", "__SKIA__", "__NETSTD_REFERENCE__")]
 		public  int SelectionStart
 		{
@@ -24,7 +24,7 @@ public  int SelectionStart
 			}
 		}
 		#endif
-		#if false || false || NET461 || false || __SKIA__ || __NETSTD_REFERENCE__ || false
+		#if false || false || NET461 || false || false || __NETSTD_REFERENCE__ || false
 		[global::Uno.NotImplemented("NET461", "__SKIA__", "__NETSTD_REFERENCE__")]
 		public  int SelectionLength
 		{

src/Uno.UI/UI/Xaml/Controls/TextBox/ITextBoxExtension.skia.cs

@@ -19,5 +19,9 @@ internal interface ITextBoxViewExtension
 		void SetIsPassword(bool isPassword);
 
 		void Select(int start, int length);
+
+		int GetSelectionStart();
+
+		int GetSelectionLength();
 	}
 }

src/Uno.UI/UI/Xaml/Controls/TextBox/TextBox.cs

@@ -788,7 +788,13 @@ public void Select(int start, int length)
 				length = textLength - start;
 			}
 
+			if (SelectionStart == start && SelectionLength == length)
+			{
+				return;
+			}
+
 			SelectPartial(start, length);
+			OnSelectionChanged();
 		}
 
 		partial void SelectPartial(int start, int length);

src/Uno.UI/UI/Xaml/Controls/TextBox/TextBox.skia.cs

@@ -30,6 +30,19 @@ partial void SelectPartial(int start, int length)
 
 		public void SelectAll() => Select(0, Text.Length);
 
+		public int SelectionStart
+		{
+			get => _textBoxView?.GetSelectionStart() ?? 0;
+			set => Select(start: value, length: SelectionLength);
+		}
+
+		public int SelectionLength
+		{
+			get => _textBoxView?.GetSelectionLength() ?? 0;
+			set => Select(SelectionStart, value);
+		}
+
+
 		protected void SetIsPassword(bool isPassword) => _textBoxView?.SetIsPassword(isPassword);
 	}
 }

src/Uno.UI/UI/Xaml/Controls/TextBox/TextBoxView.skia.cs

@@ -44,8 +44,13 @@ public TextBox? TextBox
 			}
 		}
 
+		internal int GetSelectionStart() => _textBoxExtension?.GetSelectionStart() ?? 0;
+
+		internal int GetSelectionLength() => _textBoxExtension?.GetSelectionLength() ?? 0;
+
 		public TextBlock DisplayBlock { get; } = new TextBlock();
 
+
 		internal void SetTextNative(string text)
 		{
 			// TODO: Inheritance hierarchy is wrong in Uno. PasswordBox shouldn't inherit TextBox.