Intrinsic Width fixes for RenderParagraph (#70236)

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

@@ -395,42 +395,36 @@ class RenderParagraph extends RenderBox
     RenderBox? child = firstChild;
     final List<PlaceholderDimensions> placeholderDimensions = List<PlaceholderDimensions>.filled(childCount, PlaceholderDimensions.empty, growable: false);
     int childIndex = 0;
-    // Takes textScaleFactor into account because the content of the placeholder
-    // span will be scale up when it paints.
-    height = height / textScaleFactor;
     while (child != null) {
       // Height and baseline is irrelevant as all text will be laid
-      // out in a single line.
+      // out in a single line. Therefore, using 0.0 as a dummy for the height.
       placeholderDimensions[childIndex] = PlaceholderDimensions(
-        size: Size(child.getMaxIntrinsicWidth(height), height),
+        size: Size(child.getMaxIntrinsicWidth(double.infinity), 0.0),
         alignment: _placeholderSpans[childIndex].alignment,
         baseline: _placeholderSpans[childIndex].baseline,
       );
       child = childAfter(child);
       childIndex += 1;
     }
-    _textPainter.setPlaceholderDimensions(placeholderDimensions.cast<PlaceholderDimensions>());
+    _textPainter.setPlaceholderDimensions(placeholderDimensions);
   }
 
   void _computeChildrenWidthWithMinIntrinsics(double height) {
     RenderBox? child = firstChild;
     final List<PlaceholderDimensions> placeholderDimensions = List<PlaceholderDimensions>.filled(childCount, PlaceholderDimensions.empty, growable: false);
     int childIndex = 0;
-    // Takes textScaleFactor into account because the content of the placeholder
-    // span will be scale up when it paints.
-    height = height / textScaleFactor;
     while (child != null) {
-      final double intrinsicWidth = child.getMinIntrinsicWidth(height);
-      final double intrinsicHeight = child.getMinIntrinsicHeight(intrinsicWidth);
+      // Height and baseline is irrelevant; only looking for the widest word or
+      // placeholder. Therefore, using 0.0 as a dummy for height.
       placeholderDimensions[childIndex] = PlaceholderDimensions(
-        size: Size(intrinsicWidth, intrinsicHeight),
+        size: Size(child.getMinIntrinsicWidth(double.infinity), 0.0),
         alignment: _placeholderSpans[childIndex].alignment,
         baseline: _placeholderSpans[childIndex].baseline,
       );
       child = childAfter(child);
       childIndex += 1;
     }
-    _textPainter.setPlaceholderDimensions(placeholderDimensions.cast<PlaceholderDimensions>());
+    _textPainter.setPlaceholderDimensions(placeholderDimensions);
   }
 
   void _computeChildrenHeightWithMinIntrinsics(double width) {
@@ -451,7 +445,7 @@ class RenderParagraph extends RenderBox
       child = childAfter(child);
       childIndex += 1;
     }
-    _textPainter.setPlaceholderDimensions(placeholderDimensions.cast<PlaceholderDimensions>());
+    _textPainter.setPlaceholderDimensions(placeholderDimensions);
   }
 
   @override
@@ -593,7 +587,7 @@ class RenderParagraph extends RenderBox
       child = childAfter(child);
       childIndex += 1;
     }
-    _placeholderDimensions = placeholderDimensions.cast<PlaceholderDimensions>();
+    _placeholderDimensions = placeholderDimensions;
   }
 
   // Iterate through the laid-out children and set the parentData offsets based

packages/flutter/test/widgets/text_test.dart

@@ -4,6 +4,7 @@
 
 import 'dart:ui' as ui;
 
+import 'package:flutter/rendering.dart';
 import 'package:flutter_test/flutter_test.dart';
 import 'package:flutter/foundation.dart';
 import 'package:flutter/gestures.dart';
@@ -1209,6 +1210,47 @@ void main() {
     ignoreTransform: true,
     ));
   }, semanticsEnabled: true, skip: isBrowser); // Browser does not support widget span
+
+  testWidgets('RenderParagraph intrinsic width', (WidgetTester tester) async {
+    await tester.pumpWidget(
+      Directionality(
+        textDirection: TextDirection.ltr,
+        child: Center(
+          child: Container(
+            height: 100,
+            child: IntrinsicWidth(
+              child: RichText(
+                text: TextSpan(
+                  style: const TextStyle(fontSize: 16, height: 1),
+                  children: <InlineSpan>[
+                    const TextSpan(text: 'S '),
+                    WidgetSpan(
+                      alignment: PlaceholderAlignment.top,
+                      child: Wrap(
+                        direction: Axis.vertical,
+                        children: <Widget>[
+                          Container(width: 200, height: 100),
+                          Container(width: 200, height: 30),
+                        ],
+                      ),
+                    ),
+                    const TextSpan(text: ' E'),
+                  ],
+                ),
+              ),
+            ),
+          ),
+        ),
+      ),
+    );
+
+    expect(tester.getSize(find.byType(RichText)).width, 200 + 4 * 16.0);
+    final RenderParagraph paragraph = tester.renderObject<RenderParagraph>(find.byType(RichText));
+    // The inline spans are rendered on one (horizontal) line, the sum of the widths is the max intrinsic width.
+    expect(paragraph.getMaxIntrinsicWidth(0.0), 200 + 4 * 16.0);
+    // The inline spans are rendered in one vertical run, the widest one determines the min intrinsic width.
+    expect(paragraph.getMinIntrinsicWidth(0.0), 200, skip: 'https://github.com/flutter/flutter/issues/70230');
+  });
 }
 
 Future<void> _pumpTextWidget({