TextBox: clear selection when moving the caret horizontally (#18255)

* TextBox: clear selection when moving the caret horizontally

* fix and add unit tests

src/Avalonia.Controls/TextBox.cs

@@ -1983,9 +1983,13 @@ namespace Avalonia.Controls
                 {
                     if (selectionStart != selectionEnd)
                     {
-                        _presenter.MoveCaretToTextPosition(direction > 0 ?
+                        // clear the selection and move to the appropriate side of previous selection
+                        var newPosition = direction > 0 ?
                             Math.Max(selectionStart, selectionEnd) :
-                            Math.Min(selectionStart, selectionEnd));
+                            Math.Min(selectionStart, selectionEnd);
+                        SetCurrentValue(SelectionStartProperty, newPosition);
+                        SetCurrentValue(SelectionEndProperty, newPosition);
+                        _presenter.MoveCaretToTextPosition(newPosition);
                     }
                     else
                     {

tests/Avalonia.Controls.UnitTests/TextBoxTests.cs

@@ -1535,6 +1535,172 @@ namespace Avalonia.Controls.UnitTests
             }
         }
 
+        [Theory]
+        [InlineData(2,4)]
+        [InlineData(0,4)]
+        [InlineData(2,6)]
+        [InlineData(0,6)]
+        public void When_Selection_From_Left_To_Right_Pressing_Right_Should_Remove_Selection_Moving_Caret_To_End_Of_Previous_Selection(int selectionStart, int selectionEnd)
+        {
+            using (UnitTestApplication.Start(Services))
+            {
+                var tb = new TextBox
+                {
+                    Template = CreateTemplate(),
+                    Text = "ABCDEF"
+                };
+
+                tb.Measure(Size.Infinity);
+                tb.CaretIndex = selectionStart;
+                tb.SelectionStart = selectionStart;
+                tb.SelectionEnd = selectionEnd;
+
+                RaiseKeyEvent(tb, Key.Right, KeyModifiers.None);
+
+                Assert.Equal(selectionEnd, tb.SelectionStart);
+                Assert.Equal(selectionEnd, tb.SelectionEnd);
+                Assert.Equal(selectionEnd, tb.CaretIndex);
+            }
+        }
+
+        [Theory]
+        [InlineData(2,4)]
+        [InlineData(0,4)]
+        [InlineData(2,6)]
+        [InlineData(0,6)]
+        public void When_Selection_From_Left_To_Right_Pressing_Left_Should_Remove_Selection_Moving_Caret_To_Start_Of_Previous_Selection(int selectionStart, int selectionEnd)
+        {
+            using (UnitTestApplication.Start(Services))
+            {
+                var tb = new TextBox
+                {
+                    Template = CreateTemplate(),
+                    Text = "ABCDEF"
+                };
+
+                tb.Measure(Size.Infinity);
+                tb.CaretIndex = selectionStart;
+                tb.SelectionStart = selectionStart;
+                tb.SelectionEnd = selectionEnd;
+
+                RaiseKeyEvent(tb, Key.Left, KeyModifiers.None);
+
+                Assert.Equal(selectionStart, tb.SelectionStart);
+                Assert.Equal(selectionStart, tb.SelectionEnd);
+                Assert.Equal(selectionStart, tb.CaretIndex);
+            }
+        }
+
+        [Theory]
+        [InlineData(4,2)]
+        [InlineData(4,0)]
+        [InlineData(6,2)]
+        [InlineData(6,0)]
+        public void When_Selection_From_Right_To_Left_Pressing_Right_Should_Remove_Selection_Moving_Caret_To_Start_Of_Previous_Selection(int selectionStart, int selectionEnd)
+        {
+            using (UnitTestApplication.Start(Services))
+            {
+                var tb = new TextBox
+                {
+                    Template = CreateTemplate(),
+                    Text = "ABCDEF"
+                };
+
+                tb.Measure(Size.Infinity);
+                tb.CaretIndex = selectionStart;
+                tb.SelectionStart = selectionStart;
+                tb.SelectionEnd = selectionEnd;
+
+                RaiseKeyEvent(tb, Key.Right, KeyModifiers.None);
+
+                Assert.Equal(selectionStart, tb.SelectionStart);
+                Assert.Equal(selectionStart, tb.SelectionEnd);
+                Assert.Equal(selectionStart, tb.CaretIndex);
+            }
+        }
+
+        [Theory]
+        [InlineData(4,2)]
+        [InlineData(4,0)]
+        [InlineData(6,2)]
+        [InlineData(6,0)]
+        public void When_Selection_From_Right_To_Left_Pressing_Left_Should_Remove_Selection_Moving_Caret_To_End_Of_Previous_Selection(int selectionStart, int selectionEnd)
+        {
+            using (UnitTestApplication.Start(Services))
+            {
+                var tb = new TextBox
+                {
+                    Template = CreateTemplate(),
+                    Text = "ABCDEF"
+                };
+
+                tb.Measure(Size.Infinity);
+                tb.CaretIndex = selectionStart;
+                tb.SelectionStart = selectionStart;
+                tb.SelectionEnd = selectionEnd;
+
+                RaiseKeyEvent(tb, Key.Left, KeyModifiers.None);
+
+                Assert.Equal(selectionEnd, tb.SelectionStart);
+                Assert.Equal(selectionEnd, tb.SelectionEnd);
+                Assert.Equal(selectionEnd, tb.CaretIndex);
+            }
+        }
+
+        [Theory]
+        [InlineData(0)]
+        [InlineData(2)]
+        [InlineData(4)]
+        [InlineData(6)]
+        public void When_Select_All_From_Position_Left_Should_Remove_Selection_Moving_Caret_To_Start(int caretIndex)
+        {
+            using (UnitTestApplication.Start(Services))
+            {
+                var tb = new TextBox
+                {
+                    Template = CreateTemplate(),
+                    Text = "ABCDEF"
+                };
+
+                tb.Measure(Size.Infinity);
+                tb.CaretIndex = caretIndex;
+
+                RaiseKeyEvent(tb, Key.A, KeyModifiers.Control);
+                RaiseKeyEvent(tb, Key.Left, KeyModifiers.None);
+
+                Assert.Equal(0, tb.SelectionStart);
+                Assert.Equal(0, tb.SelectionEnd);
+                Assert.Equal(0, tb.CaretIndex);
+            }
+        }
+
+        [Theory]
+        [InlineData(0)]
+        [InlineData(2)]
+        [InlineData(4)]
+        [InlineData(6)]
+        public void When_Select_All_From_Position_Right_Should_Remove_Selection_Moving_Caret_To_End(int caretIndex)
+        {
+            using (UnitTestApplication.Start(Services))
+            {
+                var tb = new TextBox
+                {
+                    Template = CreateTemplate(),
+                    Text = "ABCDEF"
+                };
+
+                tb.Measure(Size.Infinity);
+                tb.CaretIndex = caretIndex;
+
+                RaiseKeyEvent(tb, Key.A, KeyModifiers.Control);
+                RaiseKeyEvent(tb, Key.Right, KeyModifiers.None);
+
+                Assert.Equal(tb.Text.Length, tb.SelectionStart);
+                Assert.Equal(tb.Text.Length, tb.SelectionEnd);
+                Assert.Equal(tb.Text.Length, tb.CaretIndex);
+            }
+        }
+
         [Fact]
         public void TextBox_In_AdornerLayer_Will_Not_Cause_Collection_Modified_In_VisualLayerManager_Measure()
         {