Bring into view upon selection extension

When extending selection, have scroll controller jump to the most appropriate offset to display selection extension

Author: singerdmx

lib/src/widgets/box.dart

@@ -16,24 +16,107 @@ abstract class RenderContentProxyBox implements RenderBox {
   List<TextBox> getBoxesForSelection(TextSelection textSelection);
 }
 
+/// Base class for render boxes of editable content.
+///
+/// Implementations of this class usually work as a wrapper around
+/// regular (non-editable) render boxes which implement
+/// [RenderContentProxyBox].
 abstract class RenderEditableBox extends RenderBox {
+  /// The document node represented by this render box.
   Container getContainer();
 
+  /// Returns preferred line height at specified `position` in text.
+  ///
+  /// The `position` parameter must be relative to the [node]'s content.
   double preferredLineHeight(TextPosition position);
 
+  /// Returns the offset at which to paint the caret.
+  ///
+  /// The `position` parameter must be relative to the [node]'s content.
+  ///
+  /// Valid only after [layout].
   Offset getOffsetForCaret(TextPosition position);
 
+  /// Returns the position within the text for the given pixel offset.
+  ///
+  /// The `offset` parameter must be local to this box coordinate system.
+  ///
+  /// Valid only after [layout].
   TextPosition getPositionForOffset(Offset offset);
 
+  /// Returns the position relative to the [node] content
+  ///
+  /// The `position` must be within the [node] content
+  TextPosition globalToLocalPosition(TextPosition position);
+
+  /// Returns the position within the text which is on the line above the given
+  /// `position`.
+  ///
+  /// The `position` parameter must be relative to the [node] content.
+  ///
+  /// Primarily used with multi-line or soft-wrapping text.
+  ///
+  /// Can return `null` which indicates that the `position` is at the topmost
+  /// line in the text already.
   TextPosition? getPositionAbove(TextPosition position);
 
+  /// Returns the position within the text which is on the line below the given
+  /// `position`.
+  ///
+  /// The `position` parameter must be relative to the [node] content.
+  ///
+  /// Primarily used with multi-line or soft-wrapping text.
+  ///
+  /// Can return `null` which indicates that the `position` is at the bottommost
+  /// line in the text already.
   TextPosition? getPositionBelow(TextPosition position);
 
+  /// Returns the text range of the word at the given offset. Characters not
+  /// part of a word, such as spaces, symbols, and punctuation, have word breaks
+  /// on both sides. In such cases, this method will return a text range that
+  /// contains the given text position.
+  ///
+  /// Word boundaries are defined more precisely in Unicode Standard Annex #29
+  /// <http://www.unicode.org/reports/tr29/#Word_Boundaries>.
+  ///
+  /// The `position` parameter must be relative to the [node]'s content.
+  ///
+  /// Valid only after [layout].
   TextRange getWordBoundary(TextPosition position);
 
+  /// Returns the text range of the line at the given offset.
+  ///
+  /// The newline, if any, is included in the range.
+  ///
+  /// The `position` parameter must be relative to the [node]'s content.
+  ///
+  /// Valid only after [layout].
   TextRange getLineBoundary(TextPosition position);
 
+  /// Returns a list of rects that bound the given selection.
+  ///
+  /// A given selection might have more than one rect if this text painter
+  /// contains bidirectional text because logically contiguous text might not be
+  /// visually contiguous.
+  ///
+  /// Valid only after [layout].
+  // List<TextBox> getBoxesForSelection(TextSelection selection);
+
+  /// Returns a point for the base selection handle used on touch-oriented
+  /// devices.
+  ///
+  /// The `selection` parameter is expected to be in local offsets to this
+  /// render object's [node].
   TextSelectionPoint getBaseEndpointForSelection(TextSelection textSelection);
 
+  /// Returns a point for the extent selection handle used on touch-oriented
+  /// devices.
+  ///
+  /// The `selection` parameter is expected to be in local offsets to this
+  /// render object's [node].
   TextSelectionPoint getExtentEndpointForSelection(TextSelection textSelection);
+
+  /// Returns the [Rect] in local coordinates for the caret at the given text
+  /// position.
+  Rect getLocalRectForCaret(TextPosition position);
 }

lib/src/widgets/cursor.dart

@@ -292,8 +292,7 @@ class CursorPainter {
       }
     }
 
-    final pixelPerfectOffset =
-        _getPixelPerfectCursorOffset(editable!, caretRect, devicePixelRatio);
+    final pixelPerfectOffset = _getPixelPerfectCursorOffset(caretRect);
     if (!pixelPerfectOffset.isFinite) {
       return;
     }
@@ -309,11 +308,9 @@ class CursorPainter {
   }
 
   Offset _getPixelPerfectCursorOffset(
-    RenderContentProxyBox editable,
     Rect caretRect,
-    double devicePixelRatio,
   ) {
-    final caretPosition = editable.localToGlobal(caretRect.topLeft);
+    final caretPosition = editable!.localToGlobal(caretRect.topLeft);
     final pixelMultiple = 1.0 / devicePixelRatio;
 
     final pixelPerfectOffsetX = caretPosition.dx.isFinite

lib/src/widgets/editor.dart

@@ -47,6 +47,8 @@ const linkPrefixes = [
 ];
 
 abstract class EditorState extends State<RawEditor> {
+  ScrollController get scrollController;
+
   TextEditingValue getTextEditingValue();
 
   void setTextEditingValue(TextEditingValue value);
@@ -62,32 +64,75 @@ abstract class EditorState extends State<RawEditor> {
   void requestKeyboard();
 }
 
+/// Base interface for editable render objects.
 abstract class RenderAbstractEditor {
   TextSelection selectWordAtPosition(TextPosition position);
 
   TextSelection selectLineAtPosition(TextPosition position);
 
+  /// Returns preferred line height at specified `position` in text.
   double preferredLineHeight(TextPosition position);
 
+  /// Returns [Rect] for caret in local coordinates
+  ///
+  /// Useful to enforce visibility of full caret at given position
+  Rect getLocalRectForCaret(TextPosition position);
+
+  /// Returns the local coordinates of the endpoints of the given selection.
+  ///
+  /// If the selection is collapsed (and therefore occupies a single point), the
+  /// returned list is of length one. Otherwise, the selection is not collapsed
+  /// and the returned list is of length two. In this case, however, the two
+  /// points might actually be co-located (e.g., because of a bidirectional
+  /// selection that contains some text but whose ends meet in the middle).
   TextPosition getPositionForOffset(Offset offset);
 
   List<TextSelectionPoint> getEndpointsForSelection(
       TextSelection textSelection);
 
+  /// If [ignorePointer] is false (the default) then this method is called by
+  /// the internal gesture recognizer's [TapGestureRecognizer.onTapDown]
+  /// callback.
+  ///
+  /// When [ignorePointer] is true, an ancestor widget must respond to tap
+  /// down events by calling this method.
   void handleTapDown(TapDownDetails details);
 
+  /// Selects the set words of a paragraph in a given range of global positions.
+  ///
+  /// The first and last endpoints of the selection will always be at the
+  /// beginning and end of a word respectively.
+  ///
+  /// {@macro flutter.rendering.editable.select}
   void selectWordsInRange(
     Offset from,
     Offset to,
     SelectionChangedCause cause,
   );
 
+  /// Move the selection to the beginning or end of a word.
+  ///
+  /// {@macro flutter.rendering.editable.select}
   void selectWordEdge(SelectionChangedCause cause);
 
+  /// Select text between the global positions [from] and [to].
   void selectPositionAt(Offset from, Offset to, SelectionChangedCause cause);
 
+  /// Select a word around the location of the last tap down.
+  ///
+  /// {@macro flutter.rendering.editable.select}
   void selectWord(SelectionChangedCause cause);
 
+  /// Move selection to the location of the last tap down.
+  ///
+  /// {@template flutter.rendering.editable.select}
+  /// This method is mainly used to translate user inputs in global positions
+  /// into a [TextSelection]. When used in conjunction with a [EditableText],
+  /// the selection change is fed back into [TextEditingController.selection].
+  ///
+  /// If you have a [TextEditingController], it's generally easier to
+  /// programmatically manipulate its `value` or `selection` directly.
+  /// {@endtemplate}
   void selectPosition(SelectionChangedCause cause);
 }
 
@@ -988,7 +1033,8 @@ class RenderEditor extends RenderEditableContainerBox
 
     final caretTop = endpoint.point.dy -
         child.preferredLineHeight(TextPosition(
-            offset: selection.extentOffset - child.getContainer().offset)) -
+            offset:
+                selection.extentOffset - child.getContainer().documentOffset)) -
         kMargin +
         offsetInViewport +
         scrollBottomInset;
@@ -1005,6 +1051,17 @@ class RenderEditor extends RenderEditableContainerBox
     }
     return math.max(dy, 0);
   }
+
+  @override
+  Rect getLocalRectForCaret(TextPosition position) {
+    final targetChild = childAtPosition(position);
+    final localPosition = targetChild.globalToLocalPosition(position);
+
+    final childLocalRect = targetChild.getLocalRectForCaret(localPosition);
+
+    final boxParentData = targetChild.parentData as BoxParentData;
+    return childLocalRect.shift(Offset(0, boxParentData.offset.dy));
+  }
 }
 
 class EditableContainerParentData

lib/src/widgets/raw_editor.dart

@@ -115,7 +115,9 @@ class RawEditorState extends EditorState
   EditorTextSelectionOverlay? getSelectionOverlay() => _selectionOverlay;
   EditorTextSelectionOverlay? _selectionOverlay;
 
-  ScrollController? _scrollController;
+  @override
+  ScrollController get scrollController => _scrollController;
+  late ScrollController _scrollController;
 
   late CursorCont _cursorCont;
 
@@ -323,7 +325,7 @@ class RawEditorState extends EditorState
     });
 
     _scrollController = widget.scrollController;
-    _scrollController!.addListener(_updateSelectionOverlayForScroll);
+    _scrollController.addListener(_updateSelectionOverlayForScroll);
 
     _cursorCont = CursorCont(
       show: ValueNotifier<bool>(widget.showCursor),
@@ -392,9 +394,9 @@ class RawEditorState extends EditorState
     }
 
     if (widget.scrollController != _scrollController) {
-      _scrollController!.removeListener(_updateSelectionOverlayForScroll);
+      _scrollController.removeListener(_updateSelectionOverlayForScroll);
       _scrollController = widget.scrollController;
-      _scrollController!.addListener(_updateSelectionOverlayForScroll);
+      _scrollController.addListener(_updateSelectionOverlayForScroll);
     }
 
     if (widget.focusNode != oldWidget.focusNode) {
@@ -570,16 +572,16 @@ class RawEditorState extends EditorState
         final viewport = RenderAbstractViewport.of(renderEditor);
         final editorOffset =
             renderEditor.localToGlobal(const Offset(0, 0), ancestor: viewport);
-        final offsetInViewport = _scrollController!.offset + editorOffset.dy;
+        final offsetInViewport = _scrollController.offset + editorOffset.dy;
 
         final offset = renderEditor.getOffsetToRevealCursor(
-          _scrollController!.position.viewportDimension,
-          _scrollController!.offset,
+          _scrollController.position.viewportDimension,
+          _scrollController.offset,
           offsetInViewport,
         );
 
         if (offset != null) {
-          _scrollController!.animateTo(
+          _scrollController.animateTo(
             offset,
             duration: const Duration(milliseconds: 100),
             curve: Curves.fastOutSlowIn,

lib/src/widgets/raw_editor/raw_editor_state_selection_delegate_mixin.dart

@@ -1,3 +1,6 @@
+import 'dart:math';
+
+import 'package:flutter/rendering.dart';
 import 'package:flutter/widgets.dart';
 
 import '../editor.dart';
@@ -16,7 +19,57 @@ mixin RawEditorStateSelectionDelegateMixin on EditorState
 
   @override
   void bringIntoView(TextPosition position) {
-    // TODO: implement bringIntoView
+    final localRect = getRenderEditor()!.getLocalRectForCaret(position);
+    final targetOffset = _getOffsetToRevealCaret(localRect, position);
+
+    scrollController.jumpTo(targetOffset.offset);
+    getRenderEditor()!.showOnScreen(rect: targetOffset.rect);
+  }
+
+  // Finds the closest scroll offset to the current scroll offset that fully
+  // reveals the given caret rect. If the given rect's main axis extent is too
+  // large to be fully revealed in `renderEditable`, it will be centered along
+  // the main axis.
+  //
+  // If this is a multiline EditableText (which means the Editable can only
+  // scroll vertically), the given rect's height will first be extended to match
+  // `renderEditable.preferredLineHeight`, before the target scroll offset is
+  // calculated.
+  RevealedOffset _getOffsetToRevealCaret(Rect rect, TextPosition position) {
+    if (!scrollController.position.allowImplicitScrolling) {
+      return RevealedOffset(offset: scrollController.offset, rect: rect);
+    }
+
+    final editableSize = getRenderEditor()!.size;
+    final double additionalOffset;
+    final Offset unitOffset;
+
+    // The caret is vertically centered within the line. Expand the caret's
+    // height so that it spans the line because we're going to ensure that the
+    // entire expanded caret is scrolled into view.
+    final expandedRect = Rect.fromCenter(
+      center: rect.center,
+      width: rect.width,
+      height:
+          max(rect.height, getRenderEditor()!.preferredLineHeight(position)),
+    );
+
+    additionalOffset = expandedRect.height >= editableSize.height
+        ? editableSize.height / 2 - expandedRect.center.dy
+        : 0.0
+            .clamp(expandedRect.bottom - editableSize.height, expandedRect.top);
+    unitOffset = const Offset(0, 1);
+
+    // No overscrolling when encountering tall fonts/scripts that extend past
+    // the ascent.
+    final targetOffset = (additionalOffset + scrollController.offset).clamp(
+      scrollController.position.minScrollExtent,
+      scrollController.position.maxScrollExtent,
+    );
+
+    final offsetDelta = scrollController.offset - targetOffset;
+    return RevealedOffset(
+        rect: rect.shift(unitOffset * offsetDelta), offset: targetOffset);
   }
 
   @override

lib/src/widgets/text_block.dart

@@ -527,6 +527,27 @@ class RenderEditableTextBlock extends RenderEditableContainerBox
   bool hitTestChildren(BoxHitTestResult result, {required Offset position}) {
     return defaultHitTestChildren(result, position: position);
   }
+
+  @override
+  Rect getLocalRectForCaret(TextPosition position) {
+    final child = childAtPosition(position);
+    final localPosition = TextPosition(
+      offset: position.offset - child.getContainer().offset,
+      affinity: position.affinity,
+    );
+    final parentData = child.parentData as BoxParentData;
+    return child.getLocalRectForCaret(localPosition).shift(parentData.offset);
+  }
+
+  @override
+  TextPosition globalToLocalPosition(TextPosition position) {
+    assert(getContainer().containsOffset(position.offset),
+        'The provided text position is not in the current node');
+    return TextPosition(
+      offset: position.offset - getContainer().documentOffset,
+      affinity: position.affinity,
+    );
+  }
 }
 
 class _EditableBlock extends MultiChildRenderObjectWidget {