Take paint offset into account for Editable children (#127843)

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

@@ -2459,7 +2459,7 @@ class RenderEditable extends RenderBox with RelayoutWhenSystemFontsChangeMixin,
     }
 
     _textPainter.paint(context.canvas, effectiveOffset);
-    paintInlineChildren(context, offset);
+    paintInlineChildren(context, effectiveOffset);
 
     if (foregroundChild != null) {
       context.paintChild(foregroundChild, offset);

packages/flutter/test/rendering/editable_test.dart

@@ -1558,6 +1558,45 @@ void main() {
       expect(composingRect, null);
     }, skip: isBrowser); // https://github.com/flutter/flutter/issues/61021
 
+    test('WidgetSpan render box is painted at correct offset when scrolled', () async {
+      final TextSelectionDelegate delegate = _FakeEditableTextState()
+        ..textEditingValue = const TextEditingValue(
+            text: 'test',
+            selection: TextSelection.collapsed(offset: 3),
+          );
+      final List<RenderBox> renderBoxes = <RenderBox>[
+        RenderParagraph(const TextSpan(text: 'b'), textDirection: TextDirection.ltr),
+      ];
+      final ViewportOffset viewportOffset = ViewportOffset.fixed(100.0);
+      final RenderEditable editable = RenderEditable(
+        backgroundCursorColor: Colors.grey,
+        selectionColor: Colors.black,
+        textDirection: TextDirection.ltr,
+        cursorColor: Colors.red,
+        offset: viewportOffset,
+        textSelectionDelegate: delegate,
+        startHandleLayerLink: LayerLink(),
+        endHandleLayerLink: LayerLink(),
+        maxLines: null,
+        text: TextSpan(
+          style: const TextStyle(height: 1.0, fontSize: 10.0),
+          children: <InlineSpan>[
+            const TextSpan(text: 'test'),
+            WidgetSpan(child: Container(width: 10, height: 10, color: Colors.blue)),
+          ],
+        ),
+        selection: const TextSelection.collapsed(offset: 3),
+        children: renderBoxes,
+      );
+      _applyParentData(renderBoxes, editable.text!);
+      layout(editable);
+      editable.hasFocus = true;
+      pumpFrame();
+
+      final Rect composingRect = editable.getRectForComposingRange(const TextRange(start: 4, end: 5))!;
+      expect(composingRect, const Rect.fromLTRB(40.0, -100.0, 54.0, -86.0));
+    }, skip: isBrowser); // https://github.com/flutter/flutter/issues/61021
+
     test('can compute IntrinsicWidth for WidgetSpans', () {
       // Regression test for https://github.com/flutter/flutter/issues/59316
       const double screenWidth = 1000.0;