From 619eccd2e37debfca0abf15b2a5a12af7578c4b1 Mon Sep 17 00:00:00 2001
From: gaowanqiu <meritozh@users.noreply.github.com>
Date: Sat, 29 Aug 2020 07:13:05 +0800
Subject: [PATCH] Fix negative usableCrossAxisExtent in release mode (#64441)

---
 AUTHORS                                       |  1 +
 .../lib/src/rendering/sliver_grid.dart        |  6 ++-
 .../flutter/test/widgets/slivers_test.dart    | 38 +++++++++++++++++++
 3 files changed, 43 insertions(+), 2 deletions(-)

diff --git a/AUTHORS b/AUTHORS
index 97712a36cc..e82132858f 100644
--- a/AUTHORS
+++ b/AUTHORS
@@ -64,3 +64,4 @@ Brian Wang <xinlei966@gmail.com>
 CaiJingLong <cjl_spy@163.com>
 Alex Li <google@alexv525.com>
 Ram Navan <hiramprasad@gmail.com>
+meritozh <ah841814092@gmail.com>
diff --git a/packages/flutter/lib/src/rendering/sliver_grid.dart b/packages/flutter/lib/src/rendering/sliver_grid.dart
index f21570d6b7..5470845a6c 100644
--- a/packages/flutter/lib/src/rendering/sliver_grid.dart
+++ b/packages/flutter/lib/src/rendering/sliver_grid.dart
@@ -326,7 +326,8 @@ class SliverGridDelegateWithFixedCrossAxisCount extends SliverGridDelegate {
   @override
   SliverGridLayout getLayout(SliverConstraints constraints) {
     assert(_debugAssertIsValid());
-    final double usableCrossAxisExtent = constraints.crossAxisExtent - crossAxisSpacing * (crossAxisCount - 1);
+    final double usableCrossAxisExtent = math.max(0.0,
+        constraints.crossAxisExtent - crossAxisSpacing * (crossAxisCount - 1));
     final double childCrossAxisExtent = usableCrossAxisExtent / crossAxisCount;
     final double childMainAxisExtent = childCrossAxisExtent / childAspectRatio;
     return SliverGridRegularTileLayout(
@@ -425,7 +426,8 @@ class SliverGridDelegateWithMaxCrossAxisExtent extends SliverGridDelegate {
   SliverGridLayout getLayout(SliverConstraints constraints) {
     assert(_debugAssertIsValid(constraints.crossAxisExtent));
     final int crossAxisCount = (constraints.crossAxisExtent / (maxCrossAxisExtent + crossAxisSpacing)).ceil();
-    final double usableCrossAxisExtent = constraints.crossAxisExtent - crossAxisSpacing * (crossAxisCount - 1);
+    final double usableCrossAxisExtent = math.max(0.0,
+        constraints.crossAxisExtent - crossAxisSpacing * (crossAxisCount - 1));
     final double childCrossAxisExtent = usableCrossAxisExtent / crossAxisCount;
     final double childMainAxisExtent = childCrossAxisExtent / childAspectRatio;
     return SliverGridRegularTileLayout(
diff --git a/packages/flutter/test/widgets/slivers_test.dart b/packages/flutter/test/widgets/slivers_test.dart
index c521176698..162686bb0e 100644
--- a/packages/flutter/test/widgets/slivers_test.dart
+++ b/packages/flutter/test/widgets/slivers_test.dart
@@ -308,6 +308,44 @@ void main() {
     },
   );
 
+  testWidgets(
+    'SliverGrid negative usableCrossAxisExtent',
+    (WidgetTester tester) async {
+      await tester.pumpWidget(
+        Directionality(
+          textDirection: TextDirection.ltr,
+          child: Center(
+            child: SizedBox(
+              width: 4,
+              height: 4,
+              child: CustomScrollView(
+                slivers: <Widget>[
+                  SliverGrid(
+                    gridDelegate: const SliverGridDelegateWithFixedCrossAxisCount(
+                      crossAxisCount: 2,
+                      crossAxisSpacing: 8,
+                      mainAxisSpacing: 8,
+                    ),
+                    delegate: SliverChildListDelegate(
+                      <Widget>[
+                        Container(child: const Center(child: Text('A'))),
+                        Container(child: const Center(child: Text('B'))),
+                        Container(child: const Center(child: Text('C'))),
+                        Container(child: const Center(child: Text('D'))),
+                      ],
+                    ),
+                  ),
+                ],
+              ),
+            ),
+          ),
+        ),
+      );
+
+      expect(tester.takeException(), isNull);
+    },
+  );
+
   testWidgets(
     'SliverList can handle inaccurate scroll offset due to changes in children list',
       (WidgetTester tester) async {