Fix issue 23527: Exception: RenderViewport exceeded its maximum number of layout cycles (#30809)

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

@@ -686,7 +686,8 @@ class SliverGeometry extends Diagnosticable {
   ///  * [RenderViewport.cacheExtent] for a description of a viewport's cache area.
   final double cacheExtent;
 
-  static const double _epsilon = 1e-10;
+  /// The epsilon of tolerable double precision error.
+  static const double precisionErrorTolerance = 1e-10;
 
   /// Asserts that this geometry is internally consistent.
   ///
@@ -719,8 +720,8 @@ class SliverGeometry extends Diagnosticable {
       }
       verify(maxPaintExtent != null, 'The "maxPaintExtent" is null.');
       // If the paintExtent is slightly more than the maxPaintExtent, but the difference is still less
-      // than epsilon, we will not throw the assert below.
-      if (paintExtent - maxPaintExtent > _epsilon) {
+      // than precisionErrorTolerance, we will not throw the assert below.
+      if (paintExtent - maxPaintExtent > precisionErrorTolerance) {
         verify(false,
           'The "maxPaintExtent" is less than the "paintExtent".\n' +
           _debugCompareFloats('maxPaintExtent', maxPaintExtent, 'paintExtent', paintExtent) +

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

@@ -119,7 +119,8 @@ class RenderSliverList extends RenderSliverMultiBoxAdaptor {
       }
 
       final double firstChildScrollOffset = earliestScrollOffset - paintExtentOf(firstChild);
-      if (firstChildScrollOffset < 0.0) {
+      // firstChildScrollOffset may contain double precision error
+      if (firstChildScrollOffset < -SliverGeometry.precisionErrorTolerance) {
         // The first child doesn't fit within the viewport (underflow) and
         // there may be additional children above it. Find the real first child
         // and then correct the scroll position so that there's room for all and

packages/flutter/test/rendering/slivers_block_test.dart

@@ -3,7 +3,9 @@
 // found in the LICENSE file.
 
 import 'package:flutter/rendering.dart';
+import 'package:flutter/animation.dart';
 import 'package:meta/meta.dart';
+
 import '../flutter_test_alternative.dart';
 
 import 'rendering_tester.dart';
@@ -67,6 +69,49 @@ class TestRenderSliverBoxChildManager extends RenderSliverBoxChildManager {
   void setDidUnderflow(bool value) { }
 }
 
+class ViewportOffsetSpy extends ViewportOffset {
+  ViewportOffsetSpy(this._pixels);
+
+  double _pixels;
+
+  @override
+  double get pixels => _pixels;
+
+  bool corrected = false;
+
+  @override
+  bool applyViewportDimension(double viewportDimension) => true;
+
+  @override
+  bool applyContentDimensions(double minScrollExtent, double maxScrollExtent) => true;
+
+  @override
+  void correctBy(double correction) {
+    _pixels += correction;
+    corrected = true;
+  }
+
+  @override
+  void jumpTo(double pixels) {
+    // Do nothing, not required in test.
+  }
+
+  @override
+  Future<void> animateTo(
+      double to, {
+        @required Duration duration,
+        @required Curve curve,
+      }) async {
+    // Do nothing, not required in test.
+  }
+
+  @override
+  ScrollDirection get userScrollDirection => ScrollDirection.idle;
+
+  @override
+  bool get allowImplicitScrolling => false;
+}
+
 void main() {
   test('RenderSliverList basic test - down', () {
     RenderObject inner;
@@ -254,6 +299,43 @@ void main() {
     expect(inner.geometry.scrollOffsetCorrection, isNull);
   });
 
+  test('SliverList - no correction when tiny double precision error', () {
+    RenderSliverList inner;
+    RenderBox a;
+    final TestRenderSliverBoxChildManager childManager = TestRenderSliverBoxChildManager(
+      children: <RenderBox>[
+        a = RenderSizedBox(const Size(100.0, 400.0)),
+        RenderSizedBox(const Size(100.0, 400.0)),
+        RenderSizedBox(const Size(100.0, 400.0)),
+        RenderSizedBox(const Size(100.0, 400.0)),
+        RenderSizedBox(const Size(100.0, 400.0)),
+      ],
+    );
+    inner = childManager.createRenderObject();
+    final RenderViewport root = RenderViewport(
+      axisDirection: AxisDirection.down,
+      crossAxisDirection: AxisDirection.right,
+      offset: ViewportOffset.zero(),
+      children: <RenderSliver>[
+        inner,
+      ],
+    );
+    layout(root);
+
+    final SliverMultiBoxAdaptorParentData parentData = a.parentData;
+    // Simulate double precision error.
+    parentData.layoutOffset = -0.0000000000001;
+
+    root.offset = ViewportOffset.fixed(900.0);
+    pumpFrame();
+
+    final ViewportOffsetSpy spy = ViewportOffsetSpy(0.0);
+    root.offset = spy;
+    pumpFrame();
+
+    expect(spy.corrected, false);
+  });
+
   test('SliverMultiBoxAdaptorParentData.toString', () {
     final SliverMultiBoxAdaptorParentData candidate = SliverMultiBoxAdaptorParentData();
     expect(candidate.keepAlive, isFalse);