[`RenderEditable`] report real height when `maxLines == 1`. (#112029)

packages/flutter/lib/src/painting/text_painter.dart

@@ -1154,7 +1154,7 @@ class TextPainter {
   /// Valid only after [layout] has been called.
   List<ui.LineMetrics> computeLineMetrics() {
     assert(_debugAssertTextLayoutIsValid);
-    return  _lineMetricsCache ??= _paragraph!.computeLineMetrics();
+    return _lineMetricsCache ??= _paragraph!.computeLineMetrics();
   }
 
   bool _disposed = false;

packages/flutter/lib/src/rendering/editable.dart

@@ -318,6 +318,7 @@ class RenderEditable extends RenderBox with RelayoutWhenSystemFontsChangeMixin,
          textDirection: textDirection,
          textScaleFactor: textScaleFactor,
          locale: locale,
+         maxLines: maxLines == 1 ? 1 : null,
          strutStyle: strutStyle,
          textHeightBehavior: textHeightBehavior,
          textWidthBasis: textWidthBasis,
@@ -781,8 +782,7 @@ class RenderEditable extends RenderBox with RelayoutWhenSystemFontsChangeMixin,
   // Returns the obscured text when [obscureText] is true. See
   // [obscureText] and [obscuringCharacter].
   String get _plainText {
-    _cachedPlainText ??= _textPainter.text!.toPlainText(includeSemanticsLabels: false);
-    return _cachedPlainText!;
+    return _cachedPlainText ??= _textPainter.text!.toPlainText(includeSemanticsLabels: false);
   }
 
   /// The text to display.
@@ -794,8 +794,10 @@ class RenderEditable extends RenderBox with RelayoutWhenSystemFontsChangeMixin,
     if (_textPainter.text == value) {
       return;
     }
-    _textPainter.text = value;
     _cachedPlainText = null;
+    _cachedLineBreakCount = null;
+
+    _textPainter.text = value;
     _cachedAttributedValue = null;
     _cachedCombinedSemanticsInfos = null;
     _extractPlaceholderSpans(value);
@@ -965,6 +967,11 @@ class RenderEditable extends RenderBox with RelayoutWhenSystemFontsChangeMixin,
       return;
     }
     _maxLines = value;
+
+    // Special case maxLines == 1 to keep only the first line so we can get the
+    // height of the first line in case there are hard line breaks in the text.
+    // See the `_preferredHeight` method.
+    _textPainter.maxLines = value == 1 ? 1 : null;
     markNeedsTextLayout();
   }
 
@@ -1790,42 +1797,72 @@ class RenderEditable extends RenderBox with RelayoutWhenSystemFontsChangeMixin,
   /// This does not require the layout to be updated.
   double get preferredLineHeight => _textPainter.preferredLineHeight;
 
-  double _preferredHeight(double width) {
-    // Lock height to maxLines if needed.
-    final bool lockedMax = maxLines != null && minLines == null;
-    final bool lockedBoth = minLines != null && minLines == maxLines;
-    final bool singleLine = maxLines == 1;
-    if (singleLine || lockedMax || lockedBoth) {
-      return preferredLineHeight * maxLines!;
-    }
-
-    // Clamp height to minLines or maxLines if needed.
-    final bool minLimited = minLines != null && minLines! > 1;
-    final bool maxLimited = maxLines != null;
-    if (minLimited || maxLimited) {
-      _layoutText(maxWidth: width);
-      if (minLimited && _textPainter.height < preferredLineHeight * minLines!) {
-        return preferredLineHeight * minLines!;
-      }
-      if (maxLimited && _textPainter.height > preferredLineHeight * maxLines!) {
-        return preferredLineHeight * maxLines!;
+  int? _cachedLineBreakCount;
+  // TODO(LongCatIsLooong): see if we can let ui.Paragraph estimate the number
+  // of lines
+  int _countHardLineBreaks(String text) {
+    final int? cachedValue = _cachedLineBreakCount;
+    if (cachedValue != null) {
+      return cachedValue;
+    }
+    int count = 0;
+    for (int index = 0; index < text.length; index += 1) {
+      switch (text.codeUnitAt(index)) {
+        case 0x000A: // LF
+        case 0x0085: // NEL
+        case 0x000B: // VT
+        case 0x000C: // FF, treating it as a regular line separator
+        case 0x2028: // LS
+        case 0x2029: // PS
+          count += 1;
       }
     }
+    return _cachedLineBreakCount = count;
+  }
 
-    // Set the height based on the content.
-    if (width == double.infinity) {
-      final String text = _plainText;
-      int lines = 1;
-      for (int index = 0; index < text.length; index += 1) {
-        // Count explicit line breaks.
-        if (text.codeUnitAt(index) == 0x0A) {
-          lines += 1;
-        }
+  double _preferredHeight(double width) {
+    final int? maxLines = this.maxLines;
+    final int? minLines = this.minLines ?? maxLines;
+    final double minHeight = preferredLineHeight * (minLines ?? 0);
+
+    if (maxLines == null) {
+      final double estimatedHeight;
+      if (width == double.infinity) {
+        estimatedHeight = preferredLineHeight * (_countHardLineBreaks(_plainText) + 1);
+      } else {
+        _layoutText(maxWidth: width);
+        estimatedHeight = _textPainter.height;
       }
-      return preferredLineHeight * lines;
+      return math.max(estimatedHeight, minHeight);
+    }
+    // TODO(LongCatIsLooong): this is a workaround for
+    // https://github.com/flutter/flutter/issues/112123 .
+    // Use preferredLineHeight since SkParagraph currently returns an incorrect
+    // height.
+    final TextHeightBehavior? textHeightBehavior = this.textHeightBehavior;
+    final bool usePreferredLineHeightHack = maxLines == 1
+                                         && text?.codeUnitAt(0) == null
+                                         && strutStyle != null && strutStyle != StrutStyle.disabled
+                                         && textHeightBehavior != null
+                                         && (!textHeightBehavior.applyHeightToFirstAscent || !textHeightBehavior.applyHeightToLastDescent);
+
+    // Special case maxLines == 1 since it forces the scrollable direction
+    // to be horizontal. Report the real height to prevent the text from being
+    // clipped.
+    if (maxLines == 1 && !usePreferredLineHeightHack) {
+      // The _layoutText call lays out the paragraph using infinite width when
+      // maxLines == 1. Also _textPainter.maxLines will be set to 1 so should
+      // there be any line breaks only the first line is shown.
+      assert(_textPainter.maxLines == 1);
+      _layoutText(maxWidth: width);
+      return _textPainter.height;
+    }
+    if (minLines == maxLines) {
+      return minHeight;
     }
     _layoutText(maxWidth: width);
-    return math.max(preferredLineHeight, _textPainter.height);
+    final double maxHeight = preferredLineHeight * maxLines;
+    return clampDouble(_textPainter.height, minHeight, maxHeight);
   }
 
   @override
@@ -1852,14 +1889,17 @@ class RenderEditable extends RenderBox with RelayoutWhenSystemFontsChangeMixin,
   bool hitTestChildren(BoxHitTestResult result, { required Offset position }) {
     // Hit test text spans.
     bool hitText = false;
-    final Offset effectivePosition = position - _paintOffset;
-    final TextPosition textPosition = _textPainter.getPositionForOffset(effectivePosition);
-    final InlineSpan? span = _textPainter.text!.getSpanForPosition(textPosition);
-    if (span != null && span is HitTestTarget) {
-      result.add(HitTestEntry(span as HitTestTarget));
-      hitText = true;
-    }
 
+    final InlineSpan? textSpan = _textPainter.text;
+    if (textSpan != null) {
+      final Offset effectivePosition = position - _paintOffset;
+      final TextPosition textPosition = _textPainter.getPositionForOffset(effectivePosition);
+      final Object? span = textSpan.getSpanForPosition(textPosition);
+      if (span is HitTestTarget) {
+        result.add(HitTestEntry(span));
+        hitText = true;
+      }
+    }
     // Hit test render object children
     RenderBox? child = firstChild;
     int childIndex = 0;
@@ -2359,7 +2399,8 @@ class RenderEditable extends RenderBox with RelayoutWhenSystemFontsChangeMixin,
     final Size textPainterSize = _textPainter.size;
     final double width = forceLine ? constraints.maxWidth : constraints
         .constrainWidth(_textPainter.size.width + _caretMargin);
-    size = Size(width, constraints.constrainHeight(_preferredHeight(constraints.maxWidth)));
+    final double preferredHeight = _preferredHeight(constraints.maxWidth);
+    size = Size(width, constraints.constrainHeight(preferredHeight));
     final Size contentSize = Size(textPainterSize.width + _caretMargin, textPainterSize.height);
 
     final BoxConstraints painterConstraints = BoxConstraints.tight(contentSize);
@@ -2595,8 +2636,9 @@ class RenderEditable extends RenderBox with RelayoutWhenSystemFontsChangeMixin,
       _clipRectLayer.layer = null;
       _paintContents(context, offset);
     }
-    if (selection!.isValid) {
-      _paintHandleLayers(context, getEndpointsForSelection(selection!), offset);
+    final TextSelection? selection = this.selection;
+    if (selection != null && selection.isValid) {
+      _paintHandleLayers(context, getEndpointsForSelection(selection), offset);
     }
   }
 

packages/flutter/lib/src/rendering/shifted_box.dart

@@ -31,43 +31,32 @@ abstract class RenderShiftedBox extends RenderBox with RenderObjectWithChildMixi
 
   @override
   double computeMinIntrinsicWidth(double height) {
-    if (child != null) {
-      return child!.getMinIntrinsicWidth(height);
-    }
-    return 0.0;
+    return child?.getMinIntrinsicWidth(height) ?? 0.0;
   }
 
   @override
   double computeMaxIntrinsicWidth(double height) {
-    if (child != null) {
-      return child!.getMaxIntrinsicWidth(height);
-    }
-    return 0.0;
+    return child?.getMaxIntrinsicWidth(height) ?? 0.0;
   }
 
   @override
   double computeMinIntrinsicHeight(double width) {
-    if (child != null) {
-      return child!.getMinIntrinsicHeight(width);
-    }
-    return 0.0;
+    return child?.getMinIntrinsicHeight(width) ?? 0.0;
   }
 
   @override
   double computeMaxIntrinsicHeight(double width) {
-    if (child != null) {
-      return child!.getMaxIntrinsicHeight(width);
-    }
-    return 0.0;
+    return child?.getMaxIntrinsicHeight(width) ?? 0.0;
   }
 
   @override
   double? computeDistanceToActualBaseline(TextBaseline baseline) {
     double? result;
+    final RenderBox? child = this.child;
     if (child != null) {
       assert(!debugNeedsLayout);
-      result = child!.getDistanceToActualBaseline(baseline);
-      final BoxParentData childParentData = child!.parentData! as BoxParentData;
+      result = child.getDistanceToActualBaseline(baseline);
+      final BoxParentData childParentData = child.parentData! as BoxParentData;
       if (result != null) {
         result += childParentData.offset.dy;
       }
@@ -79,22 +68,24 @@ abstract class RenderShiftedBox extends RenderBox with RenderObjectWithChildMixi
 
   @override
   void paint(PaintingContext context, Offset offset) {
+    final RenderBox? child = this.child;
     if (child != null) {
-      final BoxParentData childParentData = child!.parentData! as BoxParentData;
-      context.paintChild(child!, childParentData.offset + offset);
+      final BoxParentData childParentData = child.parentData! as BoxParentData;
+      context.paintChild(child, childParentData.offset + offset);
     }
   }
 
   @override
   bool hitTestChildren(BoxHitTestResult result, { required Offset position }) {
+    final RenderBox? child = this.child;
     if (child != null) {
-      final BoxParentData childParentData = child!.parentData! as BoxParentData;
+      final BoxParentData childParentData = child.parentData! as BoxParentData;
       return result.addWithPaintOffset(
         offset: childParentData.offset,
         position: position,
         hitTest: (BoxHitTestResult result, Offset transformed) {
           assert(transformed == position - childParentData.offset);
-          return child!.hitTest(result, position: transformed);
+          return child.hitTest(result, position: transformed);
         },
       );
     }

packages/flutter/lib/src/widgets/editable_text.dart

@@ -1139,8 +1139,8 @@ class EditableText extends StatefulWidget {
   /// [TextEditingController.addListener].
   ///
   /// [onChanged] is called before [onSubmitted] when user indicates completion
-  /// of editing, such as when pressing the "done" button on the keyboard. That default
-  /// behavior can be overridden. See [onEditingComplete] for details.
+  /// of editing, such as when pressing the "done" button on the keyboard. That
+  /// default behavior can be overridden. See [onEditingComplete] for details.
   ///
   /// {@tool dartpad}
   /// This example shows how onChanged could be used to check the TextField's

packages/flutter/test/cupertino/text_field_test.dart

@@ -5149,9 +5149,13 @@ void main() {
           height: 200.0,
           width: 200.0,
           child: Center(
-            child: CupertinoTextField(
-              controller: OverflowWidgetTextEditingController(),
-              clipBehavior: Clip.none,
+            child: SizedBox(
+              // Make sure the input field is not high enough for the WidgetSpan.
+              height: 50,
+              child: CupertinoTextField(
+                controller: OverflowWidgetTextEditingController(),
+                clipBehavior: Clip.none,
+              ),
             ),
           ),
         ),

packages/flutter/test/material/text_field_test.dart

@@ -841,9 +841,13 @@ void main() {
           height: 200,
           width: 200,
           child: Center(
-            child: TextField(
-              controller: OverflowWidgetTextEditingController(),
-              clipBehavior: Clip.none,
+            child: SizedBox(
+              // Make sure the input field is not high enough for the WidgetSpan.
+              height: 50,
+              child: TextField(
+                controller: OverflowWidgetTextEditingController(),
+                clipBehavior: Clip.none,
+              ),
             ),
           ),
         ),
@@ -9068,6 +9072,7 @@ void main() {
         home: Material(
           child: Center(
             child: TextField(
+              maxLines: null,
               controller: controller,
             ),
           ),

packages/flutter/test/rendering/editable_test.dart

@@ -95,6 +95,44 @@ void main() {
     }
   });
 
+  test('Reports the real height when maxLines is 1', () {
+    const InlineSpan tallSpan = TextSpan(
+      style: TextStyle(fontSize: 10),
+      children: <InlineSpan>[TextSpan(text: 'TALL', style: TextStyle(fontSize: 100))],
+    );
+    final BoxConstraints constraints = BoxConstraints.loose(const Size(600, 600));
+    final RenderEditable editable = RenderEditable(
+      textDirection: TextDirection.ltr,
+      startHandleLayerLink: LayerLink(),
+      endHandleLayerLink: LayerLink(),
+      offset: ViewportOffset.zero(),
+      textSelectionDelegate: _FakeEditableTextState(),
+      text: tallSpan,
+    );
+
+    layout(editable, constraints: constraints);
+    expect(editable.size.height, 100);
+  });
+
+  test('Reports the height of the first line when maxLines is 1', () {
+    final InlineSpan multilineSpan = TextSpan(
+      text: 'liiiiines\n' * 10,
+      style: const TextStyle(fontSize: 10),
+    );
+    final BoxConstraints constraints = BoxConstraints.loose(const Size(600, 600));
+    final RenderEditable editable = RenderEditable(
+      textDirection: TextDirection.ltr,
+      startHandleLayerLink: LayerLink(),
+      endHandleLayerLink: LayerLink(),
+      offset: ViewportOffset.zero(),
+      textSelectionDelegate: _FakeEditableTextState(),
+      text: multilineSpan,
+    );
+
+    layout(editable, constraints: constraints);
+    expect(editable.size.height, 10);
+  });
+
   test('Editable respect clipBehavior in describeApproximatePaintClip', () {
     final String longString = 'a' * 10000;
     final RenderEditable editable = RenderEditable(