From 51a6dce2d4f083f2af973465a30840d97f9d3ab3 Mon Sep 17 00:00:00 2001
From: ksballetba <2501226111@qq.com>
Date: Mon, 8 Aug 2022 16:04:01 +0800
Subject: [PATCH 01/21] Fix an issue that Dragging the iOS text selection
 handles is jumpy (#106703)

---
 .../src/cupertino/desktop_text_selection.dart |  8 +++++++
 .../lib/src/cupertino/text_selection.dart     |  8 +++++++
 .../src/material/desktop_text_selection.dart  |  8 +++++++
 .../lib/src/material/text_selection.dart      | 10 +++++++++
 .../lib/src/widgets/text_selection.dart       | 21 +++++++++++++++++--
 .../test/cupertino/text_field_test.dart       |  5 +++++
 .../test/widgets/editable_text_test.dart      | 10 +++++++++
 .../test/widgets/text_selection_test.dart     |  5 +++++
 8 files changed, 73 insertions(+), 2 deletions(-)

diff --git a/packages/flutter/lib/src/cupertino/desktop_text_selection.dart b/packages/flutter/lib/src/cupertino/desktop_text_selection.dart
index 037c0b059cb47..2ca0e7eb119f5 100644
--- a/packages/flutter/lib/src/cupertino/desktop_text_selection.dart
+++ b/packages/flutter/lib/src/cupertino/desktop_text_selection.dart
@@ -40,6 +40,14 @@ class _CupertinoDesktopTextSelectionControls extends TextSelectionControls {
     return Size.zero;
   }
 
+  /// Returns the offset from text selection handle to actual location in text line.
+  ///
+  /// Desktop has no text selection handles, return [Offset.zero].
+  @override
+  Offset getOffsetFromHandleToTextPosition(Size handleSize) {
+    return Offset.zero;
+  }
+
   /// Builder for the Mac-style copy/paste text selection toolbar.
   @override
   Widget buildToolbar(
diff --git a/packages/flutter/lib/src/cupertino/text_selection.dart b/packages/flutter/lib/src/cupertino/text_selection.dart
index d3be12ca2c66b..a548b69dd7db7 100644
--- a/packages/flutter/lib/src/cupertino/text_selection.dart
+++ b/packages/flutter/lib/src/cupertino/text_selection.dart
@@ -202,6 +202,14 @@ class CupertinoTextSelectionControls extends TextSelectionControls {
     );
   }
 
+  /// Returns the offset from text selection handle to actual location in text line.
+  ///
+  /// To Cupertino text selection style,handle overlaps the text line, return [Offset.zero].
+  @override
+  Offset getOffsetFromHandleToTextPosition(Size handleSize) {
+    return Offset.zero;
+  }
+
   /// Builder for iOS-style copy/paste text selection toolbar.
   @override
   Widget buildToolbar(
diff --git a/packages/flutter/lib/src/material/desktop_text_selection.dart b/packages/flutter/lib/src/material/desktop_text_selection.dart
index 62690434de3d2..02387cb945eb0 100644
--- a/packages/flutter/lib/src/material/desktop_text_selection.dart
+++ b/packages/flutter/lib/src/material/desktop_text_selection.dart
@@ -26,6 +26,14 @@ class _DesktopTextSelectionControls extends TextSelectionControls {
     return Size.zero;
   }
 
+  /// Returns the offset from text selection handle to actual location in text line.
+  ///
+  /// Desktop has no text selection handles, return [Offset.zero].
+  @override
+  Offset getOffsetFromHandleToTextPosition(Size handleSize) {
+    return Offset.zero;
+  }
+
   /// Builder for the Material-style desktop copy/paste text selection toolbar.
   @override
   Widget buildToolbar(
diff --git a/packages/flutter/lib/src/material/text_selection.dart b/packages/flutter/lib/src/material/text_selection.dart
index e56cad5c582a6..48be152d67251 100644
--- a/packages/flutter/lib/src/material/text_selection.dart
+++ b/packages/flutter/lib/src/material/text_selection.dart
@@ -26,6 +26,16 @@ class MaterialTextSelectionControls extends TextSelectionControls {
   @override
   Size getHandleSize(double textLineHeight) => const Size(_kHandleSize, _kHandleSize);
 
+  /// Returns the offset from text selection handle to actual location in text line.
+  ///
+  /// To Material text selection style,handle is located below the text line.
+  /// The OffsetX from selection handle to text line is 0.0, OffsetY is handle height;
+  /// Return [Offset(0.0, -handleSize.height)]
+  @override
+  Offset getOffsetFromHandleToTextPosition(Size handleSize) {
+    return Offset(0.0, -handleSize.height);
+  }
+
   /// Builder for material-style copy/paste text selection toolbar.
   @override
   Widget buildToolbar(
diff --git a/packages/flutter/lib/src/widgets/text_selection.dart b/packages/flutter/lib/src/widgets/text_selection.dart
index 4a125c15d582b..5cd78021766d3 100644
--- a/packages/flutter/lib/src/widgets/text_selection.dart
+++ b/packages/flutter/lib/src/widgets/text_selection.dart
@@ -275,6 +275,16 @@ abstract class TextSelectionControls {
   /// Returns the size of the selection handle.
   Size getHandleSize(double textLineHeight);
 
+  /// Returns the offset from text selection handle to actual location in text line.
+  ///
+  /// To Material text selection, handle is located below the text line.
+  /// To Cupertino text selection, handle overlaps the text line.
+  /// To Desktop text selection, has no text selection handles.
+  /// 
+  /// For different relative position from selection handle to text line,
+  /// return different offset for accurate text selection updates.
+  Offset getOffsetFromHandleToTextPosition(Size handleSize);
+
   /// Whether the current selection of the text field managed by the given
   /// `delegate` can be removed from the text field and placed into the
   /// [Clipboard].
@@ -617,7 +627,10 @@ class TextSelectionOverlay {
       renderObject.preferredLineHeight,
     );
 
-    _dragEndPosition = details.globalPosition + Offset(0.0, -handleSize.height);
+    final Offset offsetFromHandleToTextPosition = selectionControls!
+        .getOffsetFromHandleToTextPosition(handleSize);
+
+    _dragEndPosition = details.globalPosition + offsetFromHandleToTextPosition;
     final TextPosition position = renderObject.getPositionForPoint(_dragEndPosition);
 
     _selectionOverlay.showMagnifier(MagnifierOverlayInfoBearer._fromRenderEditable(
@@ -692,7 +705,11 @@ class TextSelectionOverlay {
     final Size handleSize = selectionControls!.getHandleSize(
       renderObject.preferredLineHeight,
     );
-    _dragStartPosition = details.globalPosition + Offset(0.0, -handleSize.height);
+
+    final Offset offsetFromHandleToTextPosition = selectionControls!
+        .getOffsetFromHandleToTextPosition(handleSize);
+
+    _dragStartPosition = details.globalPosition + offsetFromHandleToTextPosition;
     final TextPosition position = renderObject.getPositionForPoint(_dragStartPosition);
 
     _selectionOverlay.showMagnifier(MagnifierOverlayInfoBearer._fromRenderEditable(
diff --git a/packages/flutter/test/cupertino/text_field_test.dart b/packages/flutter/test/cupertino/text_field_test.dart
index b5ea6fcb65dd1..84db7bf3b91fa 100644
--- a/packages/flutter/test/cupertino/text_field_test.dart
+++ b/packages/flutter/test/cupertino/text_field_test.dart
@@ -59,6 +59,11 @@ class MockTextSelectionControls extends TextSelectionControls {
   Size getHandleSize(double textLineHeight) {
     throw UnimplementedError();
   }
+
+  @override
+  Offset getOffsetFromHandleToTextPosition(Size handleSize) {
+    throw UnimplementedError();
+  }
 }
 
 class PathBoundsMatcher extends Matcher {
diff --git a/packages/flutter/test/widgets/editable_text_test.dart b/packages/flutter/test/widgets/editable_text_test.dart
index c635127569717..8ef69377d6d32 100644
--- a/packages/flutter/test/widgets/editable_text_test.dart
+++ b/packages/flutter/test/widgets/editable_text_test.dart
@@ -12755,6 +12755,11 @@ class MockTextSelectionControls extends Fake implements TextSelectionControls {
     return Offset.zero;
   }
 
+  @override
+  Offset getOffsetFromHandleToTextPosition(Size handleSize) {
+    return Offset.zero;
+  }
+
   bool testCanCut = false;
   bool testCanCopy = false;
   bool testCanPaste = false;
@@ -12853,6 +12858,11 @@ class _CustomTextSelectionControls extends TextSelectionControls {
     return Size.zero;
   }
 
+  @override
+  Offset getOffsetFromHandleToTextPosition(Size handleSize) {
+    return Offset.zero;
+  }
+
   @override
   Offset getHandleAnchor(TextSelectionHandleType type, double textLineHeight) {
     return Offset.zero;
diff --git a/packages/flutter/test/widgets/text_selection_test.dart b/packages/flutter/test/widgets/text_selection_test.dart
index 09980cd962680..129b5257d92fd 100644
--- a/packages/flutter/test/widgets/text_selection_test.dart
+++ b/packages/flutter/test/widgets/text_selection_test.dart
@@ -1471,6 +1471,11 @@ class TextSelectionControlsSpy extends TextSelectionControls {
   Size getHandleSize(double textLineHeight) {
     return Size(textLineHeight, textLineHeight);
   }
+
+  @override
+  Offset getOffsetFromHandleToTextPosition(Size handleSize) {
+    return Offset.zero;
+  }
 }
 
 class FakeClipboardStatusNotifier extends ClipboardStatusNotifier {

From e5503cffcf06c7f91bcf39496af69417c6a5136d Mon Sep 17 00:00:00 2001
From: ksballetba <2501226111@qq.com>
Date: Mon, 8 Aug 2022 19:12:43 +0800
Subject: [PATCH 02/21] delete needless backspace

---
 packages/flutter/lib/src/widgets/text_selection.dart | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/packages/flutter/lib/src/widgets/text_selection.dart b/packages/flutter/lib/src/widgets/text_selection.dart
index 5cd78021766d3..8797c05b26e71 100644
--- a/packages/flutter/lib/src/widgets/text_selection.dart
+++ b/packages/flutter/lib/src/widgets/text_selection.dart
@@ -280,7 +280,7 @@ abstract class TextSelectionControls {
   /// To Material text selection, handle is located below the text line.
   /// To Cupertino text selection, handle overlaps the text line.
   /// To Desktop text selection, has no text selection handles.
-  /// 
+  ///
   /// For different relative position from selection handle to text line,
   /// return different offset for accurate text selection updates.
   Offset getOffsetFromHandleToTextPosition(Size handleSize);

From dbca95bb09f36d2b4d150f53925ac15e66a138ac Mon Sep 17 00:00:00 2001
From: ksballetba <2501226111@qq.com>
Date: Mon, 15 Aug 2022 11:19:48 +0800
Subject: [PATCH 03/21] Revert "delete needless backspace"

This reverts commit e5503cffcf06c7f91bcf39496af69417c6a5136d.
---
 packages/flutter/lib/src/widgets/text_selection.dart | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/packages/flutter/lib/src/widgets/text_selection.dart b/packages/flutter/lib/src/widgets/text_selection.dart
index 8797c05b26e71..5cd78021766d3 100644
--- a/packages/flutter/lib/src/widgets/text_selection.dart
+++ b/packages/flutter/lib/src/widgets/text_selection.dart
@@ -280,7 +280,7 @@ abstract class TextSelectionControls {
   /// To Material text selection, handle is located below the text line.
   /// To Cupertino text selection, handle overlaps the text line.
   /// To Desktop text selection, has no text selection handles.
-  ///
+  /// 
   /// For different relative position from selection handle to text line,
   /// return different offset for accurate text selection updates.
   Offset getOffsetFromHandleToTextPosition(Size handleSize);

From cfdea60b8a1e91fbc18b9c3b62d5fe6d11453a98 Mon Sep 17 00:00:00 2001
From: ksballetba <2501226111@qq.com>
Date: Mon, 15 Aug 2022 11:19:57 +0800
Subject: [PATCH 04/21] Revert "Fix an issue that Dragging the iOS text
 selection handles is jumpy (#106703)"

This reverts commit 51a6dce2d4f083f2af973465a30840d97f9d3ab3.
---
 .../src/cupertino/desktop_text_selection.dart |  8 -------
 .../lib/src/cupertino/text_selection.dart     |  8 -------
 .../src/material/desktop_text_selection.dart  |  8 -------
 .../lib/src/material/text_selection.dart      | 10 ---------
 .../lib/src/widgets/text_selection.dart       | 21 ++-----------------
 .../test/cupertino/text_field_test.dart       |  5 -----
 .../test/widgets/editable_text_test.dart      | 10 ---------
 .../test/widgets/text_selection_test.dart     |  5 -----
 8 files changed, 2 insertions(+), 73 deletions(-)

diff --git a/packages/flutter/lib/src/cupertino/desktop_text_selection.dart b/packages/flutter/lib/src/cupertino/desktop_text_selection.dart
index 2ca0e7eb119f5..037c0b059cb47 100644
--- a/packages/flutter/lib/src/cupertino/desktop_text_selection.dart
+++ b/packages/flutter/lib/src/cupertino/desktop_text_selection.dart
@@ -40,14 +40,6 @@ class _CupertinoDesktopTextSelectionControls extends TextSelectionControls {
     return Size.zero;
   }
 
-  /// Returns the offset from text selection handle to actual location in text line.
-  ///
-  /// Desktop has no text selection handles, return [Offset.zero].
-  @override
-  Offset getOffsetFromHandleToTextPosition(Size handleSize) {
-    return Offset.zero;
-  }
-
   /// Builder for the Mac-style copy/paste text selection toolbar.
   @override
   Widget buildToolbar(
diff --git a/packages/flutter/lib/src/cupertino/text_selection.dart b/packages/flutter/lib/src/cupertino/text_selection.dart
index a548b69dd7db7..d3be12ca2c66b 100644
--- a/packages/flutter/lib/src/cupertino/text_selection.dart
+++ b/packages/flutter/lib/src/cupertino/text_selection.dart
@@ -202,14 +202,6 @@ class CupertinoTextSelectionControls extends TextSelectionControls {
     );
   }
 
-  /// Returns the offset from text selection handle to actual location in text line.
-  ///
-  /// To Cupertino text selection style,handle overlaps the text line, return [Offset.zero].
-  @override
-  Offset getOffsetFromHandleToTextPosition(Size handleSize) {
-    return Offset.zero;
-  }
-
   /// Builder for iOS-style copy/paste text selection toolbar.
   @override
   Widget buildToolbar(
diff --git a/packages/flutter/lib/src/material/desktop_text_selection.dart b/packages/flutter/lib/src/material/desktop_text_selection.dart
index 02387cb945eb0..62690434de3d2 100644
--- a/packages/flutter/lib/src/material/desktop_text_selection.dart
+++ b/packages/flutter/lib/src/material/desktop_text_selection.dart
@@ -26,14 +26,6 @@ class _DesktopTextSelectionControls extends TextSelectionControls {
     return Size.zero;
   }
 
-  /// Returns the offset from text selection handle to actual location in text line.
-  ///
-  /// Desktop has no text selection handles, return [Offset.zero].
-  @override
-  Offset getOffsetFromHandleToTextPosition(Size handleSize) {
-    return Offset.zero;
-  }
-
   /// Builder for the Material-style desktop copy/paste text selection toolbar.
   @override
   Widget buildToolbar(
diff --git a/packages/flutter/lib/src/material/text_selection.dart b/packages/flutter/lib/src/material/text_selection.dart
index 48be152d67251..e56cad5c582a6 100644
--- a/packages/flutter/lib/src/material/text_selection.dart
+++ b/packages/flutter/lib/src/material/text_selection.dart
@@ -26,16 +26,6 @@ class MaterialTextSelectionControls extends TextSelectionControls {
   @override
   Size getHandleSize(double textLineHeight) => const Size(_kHandleSize, _kHandleSize);
 
-  /// Returns the offset from text selection handle to actual location in text line.
-  ///
-  /// To Material text selection style,handle is located below the text line.
-  /// The OffsetX from selection handle to text line is 0.0, OffsetY is handle height;
-  /// Return [Offset(0.0, -handleSize.height)]
-  @override
-  Offset getOffsetFromHandleToTextPosition(Size handleSize) {
-    return Offset(0.0, -handleSize.height);
-  }
-
   /// Builder for material-style copy/paste text selection toolbar.
   @override
   Widget buildToolbar(
diff --git a/packages/flutter/lib/src/widgets/text_selection.dart b/packages/flutter/lib/src/widgets/text_selection.dart
index 5cd78021766d3..4a125c15d582b 100644
--- a/packages/flutter/lib/src/widgets/text_selection.dart
+++ b/packages/flutter/lib/src/widgets/text_selection.dart
@@ -275,16 +275,6 @@ abstract class TextSelectionControls {
   /// Returns the size of the selection handle.
   Size getHandleSize(double textLineHeight);
 
-  /// Returns the offset from text selection handle to actual location in text line.
-  ///
-  /// To Material text selection, handle is located below the text line.
-  /// To Cupertino text selection, handle overlaps the text line.
-  /// To Desktop text selection, has no text selection handles.
-  /// 
-  /// For different relative position from selection handle to text line,
-  /// return different offset for accurate text selection updates.
-  Offset getOffsetFromHandleToTextPosition(Size handleSize);
-
   /// Whether the current selection of the text field managed by the given
   /// `delegate` can be removed from the text field and placed into the
   /// [Clipboard].
@@ -627,10 +617,7 @@ class TextSelectionOverlay {
       renderObject.preferredLineHeight,
     );
 
-    final Offset offsetFromHandleToTextPosition = selectionControls!
-        .getOffsetFromHandleToTextPosition(handleSize);
-
-    _dragEndPosition = details.globalPosition + offsetFromHandleToTextPosition;
+    _dragEndPosition = details.globalPosition + Offset(0.0, -handleSize.height);
     final TextPosition position = renderObject.getPositionForPoint(_dragEndPosition);
 
     _selectionOverlay.showMagnifier(MagnifierOverlayInfoBearer._fromRenderEditable(
@@ -705,11 +692,7 @@ class TextSelectionOverlay {
     final Size handleSize = selectionControls!.getHandleSize(
       renderObject.preferredLineHeight,
     );
-
-    final Offset offsetFromHandleToTextPosition = selectionControls!
-        .getOffsetFromHandleToTextPosition(handleSize);
-
-    _dragStartPosition = details.globalPosition + offsetFromHandleToTextPosition;
+    _dragStartPosition = details.globalPosition + Offset(0.0, -handleSize.height);
     final TextPosition position = renderObject.getPositionForPoint(_dragStartPosition);
 
     _selectionOverlay.showMagnifier(MagnifierOverlayInfoBearer._fromRenderEditable(
diff --git a/packages/flutter/test/cupertino/text_field_test.dart b/packages/flutter/test/cupertino/text_field_test.dart
index 84db7bf3b91fa..b5ea6fcb65dd1 100644
--- a/packages/flutter/test/cupertino/text_field_test.dart
+++ b/packages/flutter/test/cupertino/text_field_test.dart
@@ -59,11 +59,6 @@ class MockTextSelectionControls extends TextSelectionControls {
   Size getHandleSize(double textLineHeight) {
     throw UnimplementedError();
   }
-
-  @override
-  Offset getOffsetFromHandleToTextPosition(Size handleSize) {
-    throw UnimplementedError();
-  }
 }
 
 class PathBoundsMatcher extends Matcher {
diff --git a/packages/flutter/test/widgets/editable_text_test.dart b/packages/flutter/test/widgets/editable_text_test.dart
index 8ef69377d6d32..c635127569717 100644
--- a/packages/flutter/test/widgets/editable_text_test.dart
+++ b/packages/flutter/test/widgets/editable_text_test.dart
@@ -12755,11 +12755,6 @@ class MockTextSelectionControls extends Fake implements TextSelectionControls {
     return Offset.zero;
   }
 
-  @override
-  Offset getOffsetFromHandleToTextPosition(Size handleSize) {
-    return Offset.zero;
-  }
-
   bool testCanCut = false;
   bool testCanCopy = false;
   bool testCanPaste = false;
@@ -12858,11 +12853,6 @@ class _CustomTextSelectionControls extends TextSelectionControls {
     return Size.zero;
   }
 
-  @override
-  Offset getOffsetFromHandleToTextPosition(Size handleSize) {
-    return Offset.zero;
-  }
-
   @override
   Offset getHandleAnchor(TextSelectionHandleType type, double textLineHeight) {
     return Offset.zero;
diff --git a/packages/flutter/test/widgets/text_selection_test.dart b/packages/flutter/test/widgets/text_selection_test.dart
index 129b5257d92fd..09980cd962680 100644
--- a/packages/flutter/test/widgets/text_selection_test.dart
+++ b/packages/flutter/test/widgets/text_selection_test.dart
@@ -1471,11 +1471,6 @@ class TextSelectionControlsSpy extends TextSelectionControls {
   Size getHandleSize(double textLineHeight) {
     return Size(textLineHeight, textLineHeight);
   }
-
-  @override
-  Offset getOffsetFromHandleToTextPosition(Size handleSize) {
-    return Offset.zero;
-  }
 }
 
 class FakeClipboardStatusNotifier extends ClipboardStatusNotifier {

From 56f72eb06ab1c2ec1b0ad6e1d25adf207a5ff381 Mon Sep 17 00:00:00 2001
From: ksballetba <2501226111@qq.com>
Date: Mon, 15 Aug 2022 14:58:25 +0800
Subject: [PATCH 05/21] Fix an issue that Dragging the iOS text selection
 update wrongly without separate value (#106703)

---
 .../lib/src/widgets/text_selection.dart       | 43 +++++++++++++++----
 1 file changed, 35 insertions(+), 8 deletions(-)

diff --git a/packages/flutter/lib/src/widgets/text_selection.dart b/packages/flutter/lib/src/widgets/text_selection.dart
index 4a125c15d582b..e4a978366c671 100644
--- a/packages/flutter/lib/src/widgets/text_selection.dart
+++ b/packages/flutter/lib/src/widgets/text_selection.dart
@@ -613,11 +613,13 @@ class TextSelectionOverlay {
     if (!renderObject.attached) {
       return;
     }
-    final Size handleSize = selectionControls!.getHandleSize(
-      renderObject.preferredLineHeight,
-    );
 
-    _dragEndPosition = details.globalPosition + Offset(0.0, -handleSize.height);
+    ///[details.globalPosition] is the drag point,need shift to
+    ///text middle point that RenderEditable use to get [TextPosition]
+    ///and update selection for end handle.
+    final Offset offsetFromDragPointToTextMiddlePoint = _getOffsetToTextMiddlePoint(_selectionOverlay.endHandleType);
+    _dragEndPosition = details.globalPosition + offsetFromDragPointToTextMiddlePoint;
+
     final TextPosition position = renderObject.getPositionForPoint(_dragEndPosition);
 
     _selectionOverlay.showMagnifier(MagnifierOverlayInfoBearer._fromRenderEditable(
@@ -689,10 +691,13 @@ class TextSelectionOverlay {
     if (!renderObject.attached) {
       return;
     }
-    final Size handleSize = selectionControls!.getHandleSize(
-      renderObject.preferredLineHeight,
-    );
-    _dragStartPosition = details.globalPosition + Offset(0.0, -handleSize.height);
+
+    ///[details.globalPosition] is the drag point,need shift to
+    ///text middle point that RenderEditable use to get [TextPosition]
+    ///and update selection for start handle.
+    final Offset offsetFromDragPointToTextMiddlePoint = _getOffsetToTextMiddlePoint(_selectionOverlay.startHandleType);
+    _dragStartPosition = details.globalPosition + offsetFromDragPointToTextMiddlePoint;
+
     final TextPosition position = renderObject.getPositionForPoint(_dragStartPosition);
 
     _selectionOverlay.showMagnifier(MagnifierOverlayInfoBearer._fromRenderEditable(
@@ -758,6 +763,28 @@ class TextSelectionOverlay {
 
   void _handleAnyDragEnd(DragEndDetails details) => _selectionOverlay.hideMagnifier(shouldShowToolbar: !_selection.isCollapsed);
 
+  Offset _getOffsetToTextMiddlePoint(TextSelectionHandleType type) {
+    final Size handleSize = selectionControls!.getHandleSize(
+      renderObject.preferredLineHeight,
+    );
+
+    /// The drag events always happens near the center of handle.
+    /// so ues half of the handle size to shift drag point to handle anchor.
+    /// handle anchor is left top point of handle rect.
+    final Offset offsetToHandleAnchor = Offset(-handleSize.width / 2, -handleSize.height / 2);
+
+    /// [getHandleAnchor] use to shift selection end point to handle anchor.
+    /// now need shift handle anchor to selection end point.
+    /// end point is [ui.TextBox] start bottom point of first or last selected word.
+    final Offset offsetToTextEndPoint = selectionControls!.getHandleAnchor(type, renderObject.preferredLineHeight);
+
+    /// For more accurate selection updates,need shift selection end point
+    /// to selection middle point.
+    final Offset offsetToTextMiddlePoint = Offset(0.0, -renderObject.preferredLineHeight / 2);
+
+    return offsetToHandleAnchor + offsetToTextEndPoint + offsetToTextMiddlePoint;
+  }
+
   void _handleSelectionHandleChanged(TextSelection newSelection, {required bool isEnd}) {
     final TextPosition textPosition = isEnd ? newSelection.extent : newSelection.base;
     selectionDelegate.userUpdateTextEditingValue(

From 89bf0036e553d24182d15f445a3be8bfefa8b670 Mon Sep 17 00:00:00 2001
From: ksballetba <2501226111@qq.com>
Date: Mon, 15 Aug 2022 15:44:10 +0800
Subject: [PATCH 06/21] make selection update more accurately

---
 .../flutter/lib/src/widgets/text_selection.dart | 17 ++++++++++++++++-
 1 file changed, 16 insertions(+), 1 deletion(-)

diff --git a/packages/flutter/lib/src/widgets/text_selection.dart b/packages/flutter/lib/src/widgets/text_selection.dart
index e4a978366c671..5f06fe254a38e 100644
--- a/packages/flutter/lib/src/widgets/text_selection.dart
+++ b/packages/flutter/lib/src/widgets/text_selection.dart
@@ -778,9 +778,24 @@ class TextSelectionOverlay {
     /// end point is [ui.TextBox] start bottom point of first or last selected word.
     final Offset offsetToTextEndPoint = selectionControls!.getHandleAnchor(type, renderObject.preferredLineHeight);
 
+
+    double getOffsetXToTextMiddlePoint(
+      TextSelectionHandleType type,
+    ) {
+      switch (type) {
+        case TextSelectionHandleType.left:
+          return -handleSize.width / 2;
+        case TextSelectionHandleType.right:
+          return handleSize.width / 2;
+        case TextSelectionHandleType.collapsed:
+          return 0.0;
+      }
+    }
+
     /// For more accurate selection updates,need shift selection end point
     /// to selection middle point.
-    final Offset offsetToTextMiddlePoint = Offset(0.0, -renderObject.preferredLineHeight / 2);
+    final double offsetXToTextMiddlePoint = getOffsetXToTextMiddlePoint(type);
+    final Offset offsetToTextMiddlePoint = Offset(offsetXToTextMiddlePoint, -renderObject.preferredLineHeight / 2);
 
     return offsetToHandleAnchor + offsetToTextEndPoint + offsetToTextMiddlePoint;
   }

From fb728827d8794e0deee2fed2e628514310f4a4a3 Mon Sep 17 00:00:00 2001
From: ksballetba <2501226111@qq.com>
Date: Mon, 15 Aug 2022 16:43:58 +0800
Subject: [PATCH 07/21] make selection update more accurately

---
 .../lib/src/widgets/text_selection.dart       | 26 +++++--------------
 1 file changed, 7 insertions(+), 19 deletions(-)

diff --git a/packages/flutter/lib/src/widgets/text_selection.dart b/packages/flutter/lib/src/widgets/text_selection.dart
index 5f06fe254a38e..6eca1e0ffc623 100644
--- a/packages/flutter/lib/src/widgets/text_selection.dart
+++ b/packages/flutter/lib/src/widgets/text_selection.dart
@@ -771,33 +771,21 @@ class TextSelectionOverlay {
     /// The drag events always happens near the center of handle.
     /// so ues half of the handle size to shift drag point to handle anchor.
     /// handle anchor is left top point of handle rect.
-    final Offset offsetToHandleAnchor = Offset(-handleSize.width / 2, -handleSize.height / 2);
+    final double offsetYToHandleAnchor =  -handleSize.height / 2;
 
     /// [getHandleAnchor] use to shift selection end point to handle anchor.
     /// now need shift handle anchor to selection end point.
     /// end point is [ui.TextBox] start bottom point of first or last selected word.
-    final Offset offsetToTextEndPoint = selectionControls!.getHandleAnchor(type, renderObject.preferredLineHeight);
-
-
-    double getOffsetXToTextMiddlePoint(
-      TextSelectionHandleType type,
-    ) {
-      switch (type) {
-        case TextSelectionHandleType.left:
-          return -handleSize.width / 2;
-        case TextSelectionHandleType.right:
-          return handleSize.width / 2;
-        case TextSelectionHandleType.collapsed:
-          return 0.0;
-      }
-    }
+    final double offsetYToTextEndPoint = selectionControls!.getHandleAnchor(type, renderObject.preferredLineHeight).dy;
 
     /// For more accurate selection updates,need shift selection end point
     /// to selection middle point.
-    final double offsetXToTextMiddlePoint = getOffsetXToTextMiddlePoint(type);
-    final Offset offsetToTextMiddlePoint = Offset(offsetXToTextMiddlePoint, -renderObject.preferredLineHeight / 2);
+    final double offsetYToTextMiddlePoint = -renderObject.preferredLineHeight / 2;
 
-    return offsetToHandleAnchor + offsetToTextEndPoint + offsetToTextMiddlePoint;
+    /// When dragging handle and move,the pointX from drag event is accurate.
+    /// Only need to compute different offsetY from different handle.
+    final double offsetYFromDragPointToTextMiddlePoint = offsetYToHandleAnchor + offsetYToTextEndPoint + offsetYToTextMiddlePoint;
+    return Offset(0.0, offsetYFromDragPointToTextMiddlePoint);
   }
 
   void _handleSelectionHandleChanged(TextSelection newSelection, {required bool isEnd}) {

From d255009b2871a6ccd1432008ca58a8fc27ac03d4 Mon Sep 17 00:00:00 2001
From: ksballetba <2501226111@qq.com>
Date: Mon, 15 Aug 2022 19:26:25 +0800
Subject: [PATCH 08/21] add new test to make sure cupertino text field can drag
 handles to change selection correctly in multiline.

---
 .../test/cupertino/text_field_test.dart       | 98 +++++++++++++++++++
 1 file changed, 98 insertions(+)

diff --git a/packages/flutter/test/cupertino/text_field_test.dart b/packages/flutter/test/cupertino/text_field_test.dart
index b5ea6fcb65dd1..643a66497c069 100644
--- a/packages/flutter/test/cupertino/text_field_test.dart
+++ b/packages/flutter/test/cupertino/text_field_test.dart
@@ -6245,4 +6245,102 @@ void main() {
       }, variant: TargetPlatformVariant.all());
     });
   });
+
+  testWidgets('Can drag handles to change selection in multiline', (WidgetTester tester) async {
+    const String kThreeLines =
+        'First line of text is\n'
+        'Second line goes until\n'
+        'Third line of stuff';
+
+    final TextEditingController controller = TextEditingController();
+
+    await tester.pumpWidget(
+      CupertinoApp(
+        debugShowCheckedModeBanner: false,
+        home: CupertinoPageScaffold(
+          child: CupertinoTextField(
+            dragStartBehavior: DragStartBehavior.down,
+            controller: controller,
+            style: const TextStyle(color: Colors.black, fontSize: 34.0),
+            maxLines: 3,
+          ),
+        ),
+      ),
+    );
+
+    const String testValue = kThreeLines;
+    const String cutValue =
+        'First line of text is\n'
+        'Second until\n'
+        'Third line of stuff';
+    await tester.enterText(find.byType(CupertinoTextField), testValue);
+
+    // skip past scrolling animation
+    await tester.pump();
+    await tester.pump(const Duration(milliseconds: 200));
+
+    // Check that the text spans multiple lines.
+    final Offset firstPos = textOffsetToPosition(tester, testValue.indexOf('First'));
+    final Offset secondPos = textOffsetToPosition(tester, testValue.indexOf('Second'));
+    final Offset thirdPos = textOffsetToPosition(tester, testValue.indexOf('Third'));
+    final Offset middleStringPos = textOffsetToPosition(tester, testValue.indexOf('irst'));
+    expect(firstPos.dx, secondPos.dx);
+    expect(firstPos.dx, thirdPos.dx);
+    expect(firstPos.dy, lessThan(secondPos.dy));
+    expect(secondPos.dy, lessThan(thirdPos.dy));
+
+    // Double tap on the 'n' in 'until' to select the word.
+    final Offset untilPos = textOffsetToPosition(tester, testValue.indexOf('until')+1);
+    await tester.tapAt(untilPos);
+    await tester.pump(const Duration(milliseconds: 50));
+    await tester.tapAt(untilPos);
+    await tester.pumpAndSettle();
+
+    await tester.pump(const Duration(milliseconds: 200)); // skip past the frame where the opacity is zero
+
+    expect(controller.selection.baseOffset, 39);
+    expect(controller.selection.extentOffset, 44);
+
+    final RenderEditable renderEditable = findRenderEditable(tester);
+    final List<TextSelectionPoint> endpoints = globalize(
+      renderEditable.getEndpointsForSelection(controller.selection),
+      renderEditable,
+    );
+    expect(endpoints.length, 2);
+
+    final Offset offsetFromEndPointToMiddlePoint = Offset(0.0, -renderEditable.preferredLineHeight / 2);
+
+    // Drag the left handle to the second line, just after 'Second'.
+    Offset handlePos = endpoints[0].point + offsetFromEndPointToMiddlePoint;
+    Offset newHandlePos = textOffsetToPosition(tester, testValue.indexOf('Second') + 6) + offsetFromEndPointToMiddlePoint;
+    TestGesture gesture = await tester.startGesture(handlePos, pointer: 7);
+    await tester.pump();
+    await gesture.moveTo(newHandlePos);
+    await tester.pump();
+    await gesture.up();
+    await tester.pump();
+
+    expect(controller.selection.baseOffset, 28);
+    expect(controller.selection.extentOffset, 44);
+
+    // Drag the right handle to the first line, just after 'First'.
+    handlePos = endpoints[1].point + offsetFromEndPointToMiddlePoint;
+    newHandlePos = textOffsetToPosition(tester, testValue.indexOf('goes') + 4) + offsetFromEndPointToMiddlePoint;
+    gesture = await tester.startGesture(handlePos, pointer: 7);
+    await tester.pump();
+    await gesture.moveTo(newHandlePos);
+    await tester.pump();
+    await gesture.up();
+    await tester.pump();
+
+    expect(controller.selection.baseOffset, 28);
+    expect(controller.selection.extentOffset, 38);
+
+    if (!isContextMenuProvidedByPlatform) {
+      await tester.tap(find.text('Cut'));
+      await tester.pump();
+      expect(controller.selection.isCollapsed, true);
+      expect(controller.text, cutValue);
+    }
+  });
 }

From 58f1569a44c6dcba0a4672d17f7585f815ecb497 Mon Sep 17 00:00:00 2001
From: ksballetba <2501226111@qq.com>
Date: Mon, 15 Aug 2022 19:36:50 +0800
Subject: [PATCH 09/21] clean unused local variable

---
 packages/flutter/test/cupertino/text_field_test.dart | 1 -
 1 file changed, 1 deletion(-)

diff --git a/packages/flutter/test/cupertino/text_field_test.dart b/packages/flutter/test/cupertino/text_field_test.dart
index 643a66497c069..38cc0f80fb24e 100644
--- a/packages/flutter/test/cupertino/text_field_test.dart
+++ b/packages/flutter/test/cupertino/text_field_test.dart
@@ -6283,7 +6283,6 @@ void main() {
     final Offset firstPos = textOffsetToPosition(tester, testValue.indexOf('First'));
     final Offset secondPos = textOffsetToPosition(tester, testValue.indexOf('Second'));
     final Offset thirdPos = textOffsetToPosition(tester, testValue.indexOf('Third'));
-    final Offset middleStringPos = textOffsetToPosition(tester, testValue.indexOf('irst'));
     expect(firstPos.dx, secondPos.dx);
     expect(firstPos.dx, thirdPos.dx);
     expect(firstPos.dy, lessThan(secondPos.dy));

From cb07af8b40cb8f66355661606a33f89e3dc18c95 Mon Sep 17 00:00:00 2001
From: ksballetba <2501226111@qq.com>
Date: Mon, 15 Aug 2022 19:39:36 +0800
Subject: [PATCH 10/21] correct the test documentation.

---
 packages/flutter/test/cupertino/text_field_test.dart | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/packages/flutter/test/cupertino/text_field_test.dart b/packages/flutter/test/cupertino/text_field_test.dart
index 38cc0f80fb24e..93a3ff689f3ef 100644
--- a/packages/flutter/test/cupertino/text_field_test.dart
+++ b/packages/flutter/test/cupertino/text_field_test.dart
@@ -6322,7 +6322,7 @@ void main() {
     expect(controller.selection.baseOffset, 28);
     expect(controller.selection.extentOffset, 44);
 
-    // Drag the right handle to the first line, just after 'First'.
+    // Drag the right handle to the second line, just after 'goes'.
     handlePos = endpoints[1].point + offsetFromEndPointToMiddlePoint;
     newHandlePos = textOffsetToPosition(tester, testValue.indexOf('goes') + 4) + offsetFromEndPointToMiddlePoint;
     gesture = await tester.startGesture(handlePos, pointer: 7);

From 685ccaf7b19a0a553bd21a72b845850205bdea58 Mon Sep 17 00:00:00 2001
From: ksballetba <2501226111@qq.com>
Date: Mon, 15 Aug 2022 19:41:19 +0800
Subject: [PATCH 11/21] clean unused local variable.

---
 packages/flutter/test/cupertino/text_field_test.dart | 11 +++++------
 1 file changed, 5 insertions(+), 6 deletions(-)

diff --git a/packages/flutter/test/cupertino/text_field_test.dart b/packages/flutter/test/cupertino/text_field_test.dart
index 93a3ff689f3ef..17db09d87443b 100644
--- a/packages/flutter/test/cupertino/text_field_test.dart
+++ b/packages/flutter/test/cupertino/text_field_test.dart
@@ -6247,11 +6247,6 @@ void main() {
   });
 
   testWidgets('Can drag handles to change selection in multiline', (WidgetTester tester) async {
-    const String kThreeLines =
-        'First line of text is\n'
-        'Second line goes until\n'
-        'Third line of stuff';
-
     final TextEditingController controller = TextEditingController();
 
     await tester.pumpWidget(
@@ -6268,7 +6263,11 @@ void main() {
       ),
     );
 
-    const String testValue = kThreeLines;
+    const String testValue =
+        'First line of text is\n'
+        'Second line goes until\n'
+        'Third line of stuff';
+
     const String cutValue =
         'First line of text is\n'
         'Second until\n'

From cb0d598379f58e49cc0ffb6805c997af592c034c Mon Sep 17 00:00:00 2001
From: ksballetba <2501226111@qq.com>
Date: Tue, 16 Aug 2022 10:50:53 +0800
Subject: [PATCH 12/21] change nits.

---
 .../lib/src/widgets/text_selection.dart       | 33 ++++++++++---------
 .../test/cupertino/text_field_test.dart       |  9 +++--
 2 files changed, 21 insertions(+), 21 deletions(-)

diff --git a/packages/flutter/lib/src/widgets/text_selection.dart b/packages/flutter/lib/src/widgets/text_selection.dart
index 6eca1e0ffc623..1766296b065f3 100644
--- a/packages/flutter/lib/src/widgets/text_selection.dart
+++ b/packages/flutter/lib/src/widgets/text_selection.dart
@@ -614,9 +614,9 @@ class TextSelectionOverlay {
       return;
     }
 
-    ///[details.globalPosition] is the drag point,need shift to
-    ///text middle point that RenderEditable use to get [TextPosition]
-    ///and update selection for end handle.
+    // [details.globalPosition] is the drag point, it needs to be shifted
+    // to the text middle point that [RenderEditable] uses to get [TextPosition]
+    // and update selection for end handle.
     final Offset offsetFromDragPointToTextMiddlePoint = _getOffsetToTextMiddlePoint(_selectionOverlay.endHandleType);
     _dragEndPosition = details.globalPosition + offsetFromDragPointToTextMiddlePoint;
 
@@ -692,9 +692,9 @@ class TextSelectionOverlay {
       return;
     }
 
-    ///[details.globalPosition] is the drag point,need shift to
-    ///text middle point that RenderEditable use to get [TextPosition]
-    ///and update selection for start handle.
+    // [details.globalPosition] is the drag point, it needs to be shifted
+    // to the text middle point that [RenderEditable] uses to get [TextPosition]
+    // and update selection for end handle.
     final Offset offsetFromDragPointToTextMiddlePoint = _getOffsetToTextMiddlePoint(_selectionOverlay.startHandleType);
     _dragStartPosition = details.globalPosition + offsetFromDragPointToTextMiddlePoint;
 
@@ -768,22 +768,23 @@ class TextSelectionOverlay {
       renderObject.preferredLineHeight,
     );
 
-    /// The drag events always happens near the center of handle.
-    /// so ues half of the handle size to shift drag point to handle anchor.
-    /// handle anchor is left top point of handle rect.
+    // The center of the handle is where it's easier to drag, and
+    // [details.globalPosition] is probably close to center.
+    // So use half of the handle size to shift drag point to handle anchor.
+    // Handle anchor is left top point of handle rect.
     final double offsetYToHandleAnchor =  -handleSize.height / 2;
 
-    /// [getHandleAnchor] use to shift selection end point to handle anchor.
-    /// now need shift handle anchor to selection end point.
-    /// end point is [ui.TextBox] start bottom point of first or last selected word.
+    // [getHandleAnchor] use to shift selection end point to handle anchor.
+    // Now need shift handle anchor to selection end point.
+    // End point is [ui.TextBox] start bottom point of first or last selected word.
     final double offsetYToTextEndPoint = selectionControls!.getHandleAnchor(type, renderObject.preferredLineHeight).dy;
 
-    /// For more accurate selection updates,need shift selection end point
-    /// to selection middle point.
+    // For more accurate selection updates,need shift selection end point
+    // to selection middle point.
     final double offsetYToTextMiddlePoint = -renderObject.preferredLineHeight / 2;
 
-    /// When dragging handle and move,the pointX from drag event is accurate.
-    /// Only need to compute different offsetY from different handle.
+    // When dragging handle and move,the pointX from drag event is accurate.
+    // Only need to compute different offsetY from different handle.
     final double offsetYFromDragPointToTextMiddlePoint = offsetYToHandleAnchor + offsetYToTextEndPoint + offsetYToTextMiddlePoint;
     return Offset(0.0, offsetYFromDragPointToTextMiddlePoint);
   }
diff --git a/packages/flutter/test/cupertino/text_field_test.dart b/packages/flutter/test/cupertino/text_field_test.dart
index 17db09d87443b..4af817ed6ef09 100644
--- a/packages/flutter/test/cupertino/text_field_test.dart
+++ b/packages/flutter/test/cupertino/text_field_test.dart
@@ -6274,9 +6274,8 @@ void main() {
         'Third line of stuff';
     await tester.enterText(find.byType(CupertinoTextField), testValue);
 
-    // skip past scrolling animation
-    await tester.pump();
-    await tester.pump(const Duration(milliseconds: 200));
+    // Skip past scrolling animation.
+    await tester.pumpAndSettle(const Duration(milliseconds: 200));
 
     // Check that the text spans multiple lines.
     final Offset firstPos = textOffsetToPosition(tester, testValue.indexOf('First'));
@@ -6308,7 +6307,7 @@ void main() {
 
     final Offset offsetFromEndPointToMiddlePoint = Offset(0.0, -renderEditable.preferredLineHeight / 2);
 
-    // Drag the left handle to the second line, just after 'Second'.
+    // Drag the left handle to just after 'Second', still on the second line..
     Offset handlePos = endpoints[0].point + offsetFromEndPointToMiddlePoint;
     Offset newHandlePos = textOffsetToPosition(tester, testValue.indexOf('Second') + 6) + offsetFromEndPointToMiddlePoint;
     TestGesture gesture = await tester.startGesture(handlePos, pointer: 7);
@@ -6321,7 +6320,7 @@ void main() {
     expect(controller.selection.baseOffset, 28);
     expect(controller.selection.extentOffset, 44);
 
-    // Drag the right handle to the second line, just after 'goes'.
+    // Drag the right handle to just after 'goes', still on the second line.
     handlePos = endpoints[1].point + offsetFromEndPointToMiddlePoint;
     newHandlePos = textOffsetToPosition(tester, testValue.indexOf('goes') + 4) + offsetFromEndPointToMiddlePoint;
     gesture = await tester.startGesture(handlePos, pointer: 7);

From 60ba360585c117c41ac1a4b7689792f6aa81f739 Mon Sep 17 00:00:00 2001
From: ksballetba <2501226111@qq.com>
Date: Tue, 16 Aug 2022 11:45:36 +0800
Subject: [PATCH 13/21] change nits.

---
 packages/flutter/lib/src/widgets/text_selection.dart | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/packages/flutter/lib/src/widgets/text_selection.dart b/packages/flutter/lib/src/widgets/text_selection.dart
index 1766296b065f3..de83709c8434b 100644
--- a/packages/flutter/lib/src/widgets/text_selection.dart
+++ b/packages/flutter/lib/src/widgets/text_selection.dart
@@ -694,7 +694,7 @@ class TextSelectionOverlay {
 
     // [details.globalPosition] is the drag point, it needs to be shifted
     // to the text middle point that [RenderEditable] uses to get [TextPosition]
-    // and update selection for end handle.
+    // and update selection for start handle.
     final Offset offsetFromDragPointToTextMiddlePoint = _getOffsetToTextMiddlePoint(_selectionOverlay.startHandleType);
     _dragStartPosition = details.globalPosition + offsetFromDragPointToTextMiddlePoint;
 

From 73918635a53cf0735406bb5677e1dda6b8b228fb Mon Sep 17 00:00:00 2001
From: ksballetba <2501226111@qq.com>
Date: Tue, 16 Aug 2022 14:21:21 +0800
Subject: [PATCH 14/21] change nits.

---
 packages/flutter/test/cupertino/text_field_test.dart | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/packages/flutter/test/cupertino/text_field_test.dart b/packages/flutter/test/cupertino/text_field_test.dart
index 4af817ed6ef09..1067041dc9cca 100644
--- a/packages/flutter/test/cupertino/text_field_test.dart
+++ b/packages/flutter/test/cupertino/text_field_test.dart
@@ -6275,7 +6275,8 @@ void main() {
     await tester.enterText(find.byType(CupertinoTextField), testValue);
 
     // Skip past scrolling animation.
-    await tester.pumpAndSettle(const Duration(milliseconds: 200));
+    await tester.pump();
+    await tester.pump(const Duration(milliseconds: 200));
 
     // Check that the text spans multiple lines.
     final Offset firstPos = textOffsetToPosition(tester, testValue.indexOf('First'));
@@ -6293,7 +6294,8 @@ void main() {
     await tester.tapAt(untilPos);
     await tester.pumpAndSettle();
 
-    await tester.pump(const Duration(milliseconds: 200)); // skip past the frame where the opacity is zero
+    // skip past the frame where the opacity is zero
+    await tester.pump(const Duration(milliseconds: 200));
 
     expect(controller.selection.baseOffset, 39);
     expect(controller.selection.extentOffset, 44);

From 6f3805bc28c2a1a0ed961e130d372f7215f26940 Mon Sep 17 00:00:00 2001
From: ksballetba <2501226111@qq.com>
Date: Tue, 16 Aug 2022 14:30:16 +0800
Subject: [PATCH 15/21] change nits.

---
 packages/flutter/test/cupertino/text_field_test.dart | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/packages/flutter/test/cupertino/text_field_test.dart b/packages/flutter/test/cupertino/text_field_test.dart
index 1067041dc9cca..e329c24a1e994 100644
--- a/packages/flutter/test/cupertino/text_field_test.dart
+++ b/packages/flutter/test/cupertino/text_field_test.dart
@@ -6276,7 +6276,7 @@ void main() {
 
     // Skip past scrolling animation.
     await tester.pump();
-    await tester.pump(const Duration(milliseconds: 200));
+    await tester.pumpAndSettle(const Duration(milliseconds: 200));
 
     // Check that the text spans multiple lines.
     final Offset firstPos = textOffsetToPosition(tester, testValue.indexOf('First'));

From c95b2028a5041181de6d6250700294ede6929199 Mon Sep 17 00:00:00 2001
From: ksballetba <2501226111@qq.com>
Date: Thu, 18 Aug 2022 11:23:57 +0800
Subject: [PATCH 16/21] Make the comments and naming are all easy to follow.

---
 .../lib/src/widgets/text_selection.dart       | 56 +++++++++++--------
 1 file changed, 34 insertions(+), 22 deletions(-)

diff --git a/packages/flutter/lib/src/widgets/text_selection.dart b/packages/flutter/lib/src/widgets/text_selection.dart
index de83709c8434b..3ec6f2ed339ce 100644
--- a/packages/flutter/lib/src/widgets/text_selection.dart
+++ b/packages/flutter/lib/src/widgets/text_selection.dart
@@ -615,10 +615,12 @@ class TextSelectionOverlay {
     }
 
     // [details.globalPosition] is the drag point, it needs to be shifted
-    // to the text middle point that [RenderEditable] uses to get [TextPosition]
+    // to the text position point that [RenderEditable] uses to get [TextPosition]
     // and update selection for end handle.
-    final Offset offsetFromDragPointToTextMiddlePoint = _getOffsetToTextMiddlePoint(_selectionOverlay.endHandleType);
-    _dragEndPosition = details.globalPosition + offsetFromDragPointToTextMiddlePoint;
+    // Dx of text position point need to be consistent with dx of drag point.
+    // Dy of text position point need to be locate in the correct text line.
+    final Offset offsetFromHandleToTextPosition = _getOffsetToTextPositionPoint(_selectionOverlay.endHandleType);
+    _dragEndPosition = details.globalPosition + offsetFromHandleToTextPosition;
 
     final TextPosition position = renderObject.getPositionForPoint(_dragEndPosition);
 
@@ -693,10 +695,12 @@ class TextSelectionOverlay {
     }
 
     // [details.globalPosition] is the drag point, it needs to be shifted
-    // to the text middle point that [RenderEditable] uses to get [TextPosition]
+    // to the text position point that [RenderEditable] uses to get [TextPosition]
     // and update selection for start handle.
-    final Offset offsetFromDragPointToTextMiddlePoint = _getOffsetToTextMiddlePoint(_selectionOverlay.startHandleType);
-    _dragStartPosition = details.globalPosition + offsetFromDragPointToTextMiddlePoint;
+    // Dx of text position point need to be consistent with dx of drag point.
+    // Dy of text position point need to be locate in the correct text line.
+    final Offset offsetFromHandleToTextPosition = _getOffsetToTextPositionPoint(_selectionOverlay.startHandleType);
+    _dragStartPosition = details.globalPosition + offsetFromHandleToTextPosition;
 
     final TextPosition position = renderObject.getPositionForPoint(_dragStartPosition);
 
@@ -763,30 +767,38 @@ class TextSelectionOverlay {
 
   void _handleAnyDragEnd(DragEndDetails details) => _selectionOverlay.hideMagnifier(shouldShowToolbar: !_selection.isCollapsed);
 
-  Offset _getOffsetToTextMiddlePoint(TextSelectionHandleType type) {
+  // The center of the handle is where it's easier to drag, and
+  // [details.globalPosition] is probably close to center.
+  // Suppose center of handle as start point, center of correct
+  // text line as target point. Return offset from start
+  // point to target point to shift real drag point to text position
+  // point. Make sure even if the drag events happened on other position
+  // of handle, not center. The text position point always locate in
+  // correct text line.
+  Offset _getOffsetToTextPositionPoint(TextSelectionHandleType type) {
     final Size handleSize = selectionControls!.getHandleSize(
       renderObject.preferredLineHeight,
     );
 
-    // The center of the handle is where it's easier to drag, and
-    // [details.globalPosition] is probably close to center.
-    // So use half of the handle size to shift drag point to handle anchor.
-    // Handle anchor is left top point of handle rect.
-    final double offsetYToHandleAnchor =  -handleSize.height / 2;
+    // Dy of offset from center of handle to top is half of handle height.
+    // Try to shift drag point to point near handle top.
+    final double offsetYFromHandleCenterToTop =  -handleSize.height / 2;
 
-    // [getHandleAnchor] use to shift selection end point to handle anchor.
-    // Now need shift handle anchor to selection end point.
-    // End point is [ui.TextBox] start bottom point of first or last selected word.
-    final double offsetYToTextEndPoint = selectionControls!.getHandleAnchor(type, renderObject.preferredLineHeight).dy;
+    // [getHandleAnchor] use to shift selection end point to left top point
+    // of handle rect when build handle widget.
+    // Selection end point is [ui.TextBox] start bottom point of first or
+    // last selected word.
+    // Now use the dy of [getHandleAnchor] try to shift handle top to selection
+    // end point.
+    final double handleAnchorDy = selectionControls!.getHandleAnchor(type, renderObject.preferredLineHeight).dy;
 
-    // For more accurate selection updates,need shift selection end point
-    // to selection middle point.
-    final double offsetYToTextMiddlePoint = -renderObject.preferredLineHeight / 2;
+    // Try to shift selection end point to center of correct text line.
+    final double offsetYToTextLineMiddlePoint = -renderObject.preferredLineHeight / 2;
 
-    // When dragging handle and move,the pointX from drag event is accurate.
+    // When dragging handle and move,the offsetX from drag event is accurate.
     // Only need to compute different offsetY from different handle.
-    final double offsetYFromDragPointToTextMiddlePoint = offsetYToHandleAnchor + offsetYToTextEndPoint + offsetYToTextMiddlePoint;
-    return Offset(0.0, offsetYFromDragPointToTextMiddlePoint);
+    final double offsetYFromHandleToTextPosition = offsetYFromHandleCenterToTop + handleAnchorDy + offsetYToTextLineMiddlePoint;
+    return Offset(0.0, offsetYFromHandleToTextPosition);
   }
 
   void _handleSelectionHandleChanged(TextSelection newSelection, {required bool isEnd}) {

From 2ed69d381db5d2e53f56a867ef166a46e38df5d9 Mon Sep 17 00:00:00 2001
From: ksballetba <2501226111@qq.com>
Date: Thu, 18 Aug 2022 14:32:04 +0800
Subject: [PATCH 17/21] Make the comments and naming are all easy to
 understand.

---
 .../lib/src/widgets/text_selection.dart       | 34 +++++++++----------
 1 file changed, 16 insertions(+), 18 deletions(-)

diff --git a/packages/flutter/lib/src/widgets/text_selection.dart b/packages/flutter/lib/src/widgets/text_selection.dart
index 3ec6f2ed339ce..e5f9851fb8adb 100644
--- a/packages/flutter/lib/src/widgets/text_selection.dart
+++ b/packages/flutter/lib/src/widgets/text_selection.dart
@@ -615,8 +615,8 @@ class TextSelectionOverlay {
     }
 
     // [details.globalPosition] is the drag point, it needs to be shifted
-    // to the text position point that [RenderEditable] uses to get [TextPosition]
-    // and update selection for end handle.
+    // to the text position point that [RenderEditable] uses to get
+    // [TextPosition] and update selection for end handle correctly.
     // Dx of text position point need to be consistent with dx of drag point.
     // Dy of text position point need to be locate in the correct text line.
     final Offset offsetFromHandleToTextPosition = _getOffsetToTextPositionPoint(_selectionOverlay.endHandleType);
@@ -695,8 +695,8 @@ class TextSelectionOverlay {
     }
 
     // [details.globalPosition] is the drag point, it needs to be shifted
-    // to the text position point that [RenderEditable] uses to get [TextPosition]
-    // and update selection for start handle.
+    // to the text position point that [RenderEditable] uses to get
+    // [TextPosition] and update selection for start handle correctly.
     // Dx of text position point need to be consistent with dx of drag point.
     // Dy of text position point need to be locate in the correct text line.
     final Offset offsetFromHandleToTextPosition = _getOffsetToTextPositionPoint(_selectionOverlay.startHandleType);
@@ -769,10 +769,9 @@ class TextSelectionOverlay {
 
   // The center of the handle is where it's easier to drag, and
   // [details.globalPosition] is probably close to center.
-  // Suppose center of handle as start point, center of correct
-  // text line as target point. Return offset from start
-  // point to target point to shift real drag point to text position
-  // point. Make sure even if the drag events happened on other position
+  // Return offset from center of handle to center of correct
+  // text line to shift real drag point on handle to text position point.
+  // Make sure even if the drag events happened on other position
   // of handle, not center. The text position point always locate in
   // correct text line.
   Offset _getOffsetToTextPositionPoint(TextSelectionHandleType type) {
@@ -780,24 +779,23 @@ class TextSelectionOverlay {
       renderObject.preferredLineHeight,
     );
 
-    // Dy of offset from center of handle to top is half of handle height.
-    // Try to shift drag point to point near handle top.
-    final double offsetYFromHandleCenterToTop =  -handleSize.height / 2;
+    // Try to shift center of handle to top by half of handle height.
+    final double halfHandleHeight = handleSize.height / 2;
 
     // [getHandleAnchor] use to shift selection end point to left top point
     // of handle rect when build handle widget.
-    // Selection end point is [ui.TextBox] start bottom point of first or
-    // last selected word.
-    // Now use the dy of [getHandleAnchor] try to shift handle top to selection
-    // end point.
+    // End point is at bottom of selection rect, which is at the bottom of
+    // the text line too.
+    // Try to shift handle top to selection end point by dy of handle anchor.
     final double handleAnchorDy = selectionControls!.getHandleAnchor(type, renderObject.preferredLineHeight).dy;
 
-    // Try to shift selection end point to center of correct text line.
-    final double offsetYToTextLineMiddlePoint = -renderObject.preferredLineHeight / 2;
+    // Try to shift selection end point to center of correct text line
+    // by half preferred line height.
+    final double halfPreferredLineHeight = renderObject.preferredLineHeight / 2;
 
     // When dragging handle and move,the offsetX from drag event is accurate.
     // Only need to compute different offsetY from different handle.
-    final double offsetYFromHandleToTextPosition = offsetYFromHandleCenterToTop + handleAnchorDy + offsetYToTextLineMiddlePoint;
+    final double offsetYFromHandleToTextPosition = handleAnchorDy - halfHandleHeight - halfPreferredLineHeight;
     return Offset(0.0, offsetYFromHandleToTextPosition);
   }
 

From 452b7b51fc6fd39a6ca7c5777ee7ceedece96aa1 Mon Sep 17 00:00:00 2001
From: ksballetba <2501226111@qq.com>
Date: Thu, 18 Aug 2022 14:44:19 +0800
Subject: [PATCH 18/21] change nits.

---
 packages/flutter/lib/src/widgets/text_selection.dart | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/packages/flutter/lib/src/widgets/text_selection.dart b/packages/flutter/lib/src/widgets/text_selection.dart
index e5f9851fb8adb..6d441b4883881 100644
--- a/packages/flutter/lib/src/widgets/text_selection.dart
+++ b/packages/flutter/lib/src/widgets/text_selection.dart
@@ -793,7 +793,7 @@ class TextSelectionOverlay {
     // by half preferred line height.
     final double halfPreferredLineHeight = renderObject.preferredLineHeight / 2;
 
-    // When dragging handle and move,the offsetX from drag event is accurate.
+    // When dragging handle and move, the offsetX from drag event is accurate.
     // Only need to compute different offsetY from different handle.
     final double offsetYFromHandleToTextPosition = handleAnchorDy - halfHandleHeight - halfPreferredLineHeight;
     return Offset(0.0, offsetYFromHandleToTextPosition);

From 1ec5191b43fd2e537e4123e45b802f8e383dae52 Mon Sep 17 00:00:00 2001
From: ksballetba <2501226111@qq.com>
Date: Thu, 18 Aug 2022 19:11:41 +0800
Subject: [PATCH 19/21] Make the comments are easy to understand.

---
 packages/flutter/lib/src/widgets/text_selection.dart | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/packages/flutter/lib/src/widgets/text_selection.dart b/packages/flutter/lib/src/widgets/text_selection.dart
index 6d441b4883881..94ad83ee4d561 100644
--- a/packages/flutter/lib/src/widgets/text_selection.dart
+++ b/packages/flutter/lib/src/widgets/text_selection.dart
@@ -769,8 +769,8 @@ class TextSelectionOverlay {
 
   // The center of the handle is where it's easier to drag, and
   // [details.globalPosition] is probably close to center.
-  // Return offset from center of handle to center of correct
-  // text line to shift real drag point on handle to text position point.
+  // Return offset from center of handle to center of correct text line.
+  // The offset use to shift real drag point on handle to text position point.
   // Make sure even if the drag events happened on other position
   // of handle, not center. The text position point always locate in
   // correct text line.

From 6df133d42ebf266255ef22c6164a6418252980e6 Mon Sep 17 00:00:00 2001
From: ksballetba <2501226111@qq.com>
Date: Wed, 24 Aug 2022 10:32:16 +0800
Subject: [PATCH 20/21] change test case name.

---
 packages/flutter/test/cupertino/text_field_test.dart | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/packages/flutter/test/cupertino/text_field_test.dart b/packages/flutter/test/cupertino/text_field_test.dart
index e329c24a1e994..35abc0605dfe3 100644
--- a/packages/flutter/test/cupertino/text_field_test.dart
+++ b/packages/flutter/test/cupertino/text_field_test.dart
@@ -6246,7 +6246,7 @@ void main() {
     });
   });
 
-  testWidgets('Can drag handles to change selection in multiline', (WidgetTester tester) async {
+  testWidgets('Can drag handles to change selection correctly in multiline', (WidgetTester tester) async {
     final TextEditingController controller = TextEditingController();
 
     await tester.pumpWidget(

From fc6fc7edd8e8ae1e4a22f0b4f42e5de23a3da97c Mon Sep 17 00:00:00 2001
From: ksballetba <2501226111@qq.com>
Date: Tue, 25 Oct 2022 10:35:44 +0800
Subject: [PATCH 21/21] Docs improvements

---
 .../lib/src/widgets/text_selection.dart       | 40 +++++++------------
 .../test/cupertino/text_field_test.dart       |  4 +-
 2 files changed, 16 insertions(+), 28 deletions(-)

diff --git a/packages/flutter/lib/src/widgets/text_selection.dart b/packages/flutter/lib/src/widgets/text_selection.dart
index 0b3086b1ec173..825b8cf9a4b73 100644
--- a/packages/flutter/lib/src/widgets/text_selection.dart
+++ b/packages/flutter/lib/src/widgets/text_selection.dart
@@ -583,11 +583,8 @@ class TextSelectionOverlay {
       return;
     }
 
-    // [details.globalPosition] is the drag point, it needs to be shifted
-    // to the text position point that [RenderEditable] uses to get
-    // [TextPosition] and update selection for end handle correctly.
-    // Dx of text position point need to be consistent with dx of drag point.
-    // Dy of text position point need to be locate in the correct text line.
+    // This adjusts for the fact that the selection handles may not
+    // perfectly cover the TextPosition that they correspond to.
     final Offset offsetFromHandleToTextPosition = _getOffsetToTextPositionPoint(_selectionOverlay.endHandleType);
     _dragEndPosition = details.globalPosition + offsetFromHandleToTextPosition;
 
@@ -665,11 +662,8 @@ class TextSelectionOverlay {
       return;
     }
 
-    // [details.globalPosition] is the drag point, it needs to be shifted
-    // to the text position point that [RenderEditable] uses to get
-    // [TextPosition] and update selection for start handle correctly.
-    // Dx of text position point need to be consistent with dx of drag point.
-    // Dy of text position point need to be locate in the correct text line.
+    // This adjusts for the fact that the selection handles may not
+    // perfectly cover the TextPosition that they correspond to.
     final Offset offsetFromHandleToTextPosition = _getOffsetToTextPositionPoint(_selectionOverlay.startHandleType);
     _dragStartPosition = details.globalPosition + offsetFromHandleToTextPosition;
 
@@ -740,13 +734,7 @@ class TextSelectionOverlay {
 
   void _handleAnyDragEnd(DragEndDetails details) => _selectionOverlay.hideMagnifier(shouldShowToolbar: !_selection.isCollapsed);
 
-  // The center of the handle is where it's easier to drag, and
-  // [details.globalPosition] is probably close to center.
-  // Return offset from center of handle to center of correct text line.
-  // The offset use to shift real drag point on handle to text position point.
-  // Make sure even if the drag events happened on other position
-  // of handle, not center. The text position point always locate in
-  // correct text line.
+  // Returns the offset that locates a drag on a handle to the correct line of text.
   Offset _getOffsetToTextPositionPoint(TextSelectionHandleType type) {
     final Size handleSize = selectionControls!.getHandleSize(
       renderObject.preferredLineHeight,
@@ -755,19 +743,19 @@ class TextSelectionOverlay {
     // Try to shift center of handle to top by half of handle height.
     final double halfHandleHeight = handleSize.height / 2;
 
-    // [getHandleAnchor] use to shift selection end point to left top point
-    // of handle rect when build handle widget.
-    // End point is at bottom of selection rect, which is at the bottom of
-    // the text line too.
-    // Try to shift handle top to selection end point by dy of handle anchor.
+    // [getHandleAnchor] is used to shift the selection endpoint to the top left
+    // point of the handle rect when building the handle widget.
+    // The endpoint is at the bottom of the selection rect, which is also at the
+    // bottom of the line of text.
+    // Try to shift the top of the handle to the selection endpoint by the dy of
+    // the handle's anchor.
     final double handleAnchorDy = selectionControls!.getHandleAnchor(type, renderObject.preferredLineHeight).dy;
 
-    // Try to shift selection end point to center of correct text line
-    // by half preferred line height.
+    // Try to shift the selection endpoint to the center of the correct line by
+    // using half of the line height.
     final double halfPreferredLineHeight = renderObject.preferredLineHeight / 2;
 
-    // When dragging handle and move, the offsetX from drag event is accurate.
-    // Only need to compute different offsetY from different handle.
+    // The x offset is accurate, so we only need to adjust the y position.
     final double offsetYFromHandleToTextPosition = handleAnchorDy - halfHandleHeight - halfPreferredLineHeight;
     return Offset(0.0, offsetYFromHandleToTextPosition);
   }
diff --git a/packages/flutter/test/cupertino/text_field_test.dart b/packages/flutter/test/cupertino/text_field_test.dart
index 18c6e89251cc6..f646deec9186d 100644
--- a/packages/flutter/test/cupertino/text_field_test.dart
+++ b/packages/flutter/test/cupertino/text_field_test.dart
@@ -6854,7 +6854,7 @@ void main() {
     await tester.tapAt(untilPos);
     await tester.pumpAndSettle();
 
-    // skip past the frame where the opacity is zero
+    // Skip past the frame where the opacity is zero.
     await tester.pump(const Duration(milliseconds: 200));
 
     expect(controller.selection.baseOffset, 39);
@@ -6869,7 +6869,7 @@ void main() {
 
     final Offset offsetFromEndPointToMiddlePoint = Offset(0.0, -renderEditable.preferredLineHeight / 2);
 
-    // Drag the left handle to just after 'Second', still on the second line..
+    // Drag the left handle to just after 'Second', still on the second line.
     Offset handlePos = endpoints[0].point + offsetFromEndPointToMiddlePoint;
     Offset newHandlePos = textOffsetToPosition(tester, testValue.indexOf('Second') + 6) + offsetFromEndPointToMiddlePoint;
     TestGesture gesture = await tester.startGesture(handlePos, pointer: 7);