Prepare the framework for having RRect assert on negative radii (#111515)

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

@@ -392,13 +392,19 @@ class BorderRadius extends BorderRadiusGeometry {
   Radius get _bottomEnd => Radius.zero;
 
   /// Creates an [RRect] from the current border radius and a [Rect].
+  ///
+  /// If any of the radii have negative values in x or y, those values will be
+  /// clamped to zero in order to produce a valid [RRect].
   RRect toRRect(Rect rect) {
+    // Because the current radii could be negative, we must clamp them before
+    // converting them to an RRect to be rendered, since negative radii on
+    // RRects don't make sense.
     return RRect.fromRectAndCorners(
       rect,
-      topLeft: topLeft,
-      topRight: topRight,
-      bottomLeft: bottomLeft,
-      bottomRight: bottomRight,
+      topLeft: topLeft.clamp(minimum: Radius.zero), // ignore_clamp_double_lint
+      topRight: topRight.clamp(minimum: Radius.zero), // ignore_clamp_double_lint
+      bottomLeft: bottomLeft.clamp(minimum: Radius.zero), // ignore_clamp_double_lint
+      bottomRight: bottomRight.clamp(minimum: Radius.zero), // ignore_clamp_double_lint
     );
   }
 

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

@@ -232,7 +232,18 @@ abstract class BoxBorder extends ShapeBorder {
       canvas.drawRRect(borderRadius.toRRect(rect), paint);
     } else {
       final RRect borderRect = borderRadius.toRRect(rect);
-      final RRect inner = borderRect.deflate(side.strokeInset);
+      RRect inner = borderRect.deflate(side.strokeInset);
+      // Clamp the inner border's radii to zero, until deflate does this
+      // automatically, so that we can start asserting non-negative values
+      // in the engine without breaking the framework.
+      // TODO(gspencergoog): Remove this once https://github.com/flutter/engine/pull/36062 rolls into the framework.
+      inner = RRect.fromLTRBAndCorners(
+        inner.left, inner.top, inner.right, inner.bottom,
+        topLeft: inner.tlRadius.clamp(minimum: Radius.zero), // ignore_clamp_double_lint
+        topRight: inner.trRadius.clamp(minimum: Radius.zero), // ignore_clamp_double_lint
+        bottomLeft: inner.blRadius.clamp(minimum: Radius.zero), // ignore_clamp_double_lint
+        bottomRight: inner.brRadius.clamp(minimum: Radius.zero), // ignore_clamp_double_lint
+      );
       final RRect outer = borderRect.inflate(side.strokeOutset);
       canvas.drawDRRect(outer, inner, paint);
     }

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

@@ -132,7 +132,18 @@ class RoundedRectangleBorder extends OutlinedBorder {
           final Paint paint = Paint()
             ..color = side.color;
           final RRect borderRect = borderRadius.resolve(textDirection).toRRect(rect);
-          final RRect inner = borderRect.deflate(side.strokeInset);
+          RRect inner = borderRect.deflate(side.strokeInset);
+          // Clamp the inner border's radii to zero, until deflate does this
+          // automatically, so that we can start asserting non-negative values
+          // in the engine without breaking the framework.
+          // TODO(gspencergoog): Remove this once https://github.com/flutter/engine/pull/36062 rolls into the framework.
+          inner = RRect.fromLTRBAndCorners(
+            inner.left, inner.top, inner.right, inner.bottom,
+            topLeft: inner.tlRadius.clamp(minimum: Radius.zero), // ignore_clamp_double_lint
+            topRight: inner.trRadius.clamp(minimum: Radius.zero), // ignore_clamp_double_lint
+            bottomLeft: inner.blRadius.clamp(minimum: Radius.zero), // ignore_clamp_double_lint
+            bottomRight: inner.brRadius.clamp(minimum: Radius.zero), // ignore_clamp_double_lint
+          );
           final RRect outer = borderRect.inflate(side.strokeOutset);
           canvas.drawDRRect(outer, inner, paint);
         }

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

@@ -271,7 +271,18 @@ class TableBorder {
       paintBorder(canvas, rect, top: top, right: right, bottom: bottom, left: left);
     } else {
       final RRect outer = borderRadius.toRRect(rect);
-      final RRect inner = outer.deflate(top.width);
+      RRect inner = outer.deflate(top.width);
+      // Clamp the inner border's radii to zero, until deflate does this
+      // automatically, so that we can start asserting non-negative values
+      // in the engine without breaking the framework.
+      // TODO(gspencergoog): Remove this once https://github.com/flutter/engine/pull/36062 rolls into the framework.
+      inner = RRect.fromLTRBAndCorners(
+        inner.left, inner.top, inner.right, inner.bottom,
+        topLeft: inner.tlRadius.clamp(minimum: Radius.zero), // ignore_clamp_double_lint
+        topRight: inner.trRadius.clamp(minimum: Radius.zero), // ignore_clamp_double_lint
+        bottomLeft: inner.blRadius.clamp(minimum: Radius.zero), // ignore_clamp_double_lint
+        bottomRight: inner.brRadius.clamp(minimum: Radius.zero), // ignore_clamp_double_lint
+      );
       final Paint paint = Paint()..color = top.color;
       canvas.drawDRRect(outer, inner, paint);
     }

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

@@ -129,6 +129,17 @@ class _MulticastCanvas implements Canvas {
 
   @override
   void drawDRRect(RRect outer, RRect inner, Paint paint) {
+    // Clamp the inner border's radii to zero, until deflate does this
+    // automatically, so that we can start asserting non-negative values
+    // in the engine without breaking the framework.
+    // TODO(gspencergoog): Remove this once https://github.com/flutter/engine/pull/36062 rolls into the framework.
+    inner = RRect.fromLTRBAndCorners(
+      inner.left, inner.top, inner.right, inner.bottom,
+      topLeft: inner.tlRadius.clamp(minimum: Radius.zero), // ignore_clamp_double_lint
+      topRight: inner.trRadius.clamp(minimum: Radius.zero), // ignore_clamp_double_lint
+      bottomLeft: inner.blRadius.clamp(minimum: Radius.zero), // ignore_clamp_double_lint
+      bottomRight: inner.brRadius.clamp(minimum: Radius.zero), // ignore_clamp_double_lint
+    );
     _main.drawDRRect(outer, inner, paint);
     _screenshot.drawDRRect(outer, inner, paint);
   }

packages/flutter/test/material/checkbox_test.dart

@@ -553,7 +553,7 @@ void main() {
         ..drrect(
           color: material3 ? theme.colorScheme.onSurface : const Color(0x8a000000),
           outer: RRect.fromLTRBR(15.0, 15.0, 33.0, 33.0, const Radius.circular(1.0)),
-          inner: RRect.fromLTRBR(17.0, 17.0, 31.0, 31.0, const Radius.circular(-1.0)),
+          inner: RRect.fromLTRBR(17.0, 17.0, 31.0, 31.0, Radius.zero),
         ),
     );
 
@@ -568,7 +568,7 @@ void main() {
         ..drrect(
           color: material3 ? theme.colorScheme.onSurface.withOpacity(0.38) : const Color(0x61000000),
           outer: RRect.fromLTRBR(15.0, 15.0, 33.0, 33.0, const Radius.circular(1.0)),
-          inner: RRect.fromLTRBR(17.0, 17.0, 31.0, 31.0, const Radius.circular(-1.0)),
+          inner: RRect.fromLTRBR(17.0, 17.0, 31.0, 31.0, Radius.zero),
         ),
     );
   });
@@ -1420,7 +1420,7 @@ void main() {
         ..drrect(
           color: borderColor,
           outer: RRect.fromLTRBR(15, 15, 33, 33, const Radius.circular(1)),
-          inner: RRect.fromLTRBR(19, 19, 29, 29, const Radius.circular(-3)),
+          inner: RRect.fromLTRBR(19, 19, 29, 29, Radius.zero),
         ),
       );
     }
@@ -1479,7 +1479,7 @@ void main() {
         ..drrect(
           color: borderColor,
           outer: RRect.fromLTRBR(15, 15, 33, 33, const Radius.circular(1)),
-          inner: RRect.fromLTRBR(19, 19, 29, 29, const Radius.circular(-3)),
+          inner: RRect.fromLTRBR(19, 19, 29, 29, Radius.zero),
         ),
       );
     }

packages/flutter/test/widgets/box_decoration_test.dart

@@ -249,12 +249,7 @@ Future<void> main() async {
           350.0, 200.0, 450.0, 300.0,
           topRight: const Radius.circular(10.0),
         ),
-        inner: RRect.fromLTRBAndCorners(
-          360.0, 210.0, 440.0, 290.0,
-          topLeft: const Radius.circular(-10.0),
-          bottomRight: const Radius.circular(-10.0),
-          bottomLeft: const Radius.circular(-10.0),
-        ),
+        inner: RRect.fromLTRBAndCorners(360.0, 210.0, 440.0, 290.0),
       )
       ..circle(x: 400.0, y: 350.0, radius: 45.0),
     );