TableBorder.lerp and TableBorder.scale drop borderRadius

Steps to reproduce

final a = TableBorder.all(borderRadius: const BorderRadius.all(Radius.circular(4)));
final b = TableBorder.all(borderRadius: const BorderRadius.all(Radius.circular(12)));

print(TableBorder.lerp(a, b, 0.5)!.borderRadius); // BorderRadius.zero
print(b.scale(0.5).borderRadius);                 // BorderRadius.zero

Expected results

lerp interpolates the radius (8 here), and scale scales it (6 here), the same way BoxDecoration handles borderRadius.

Actual results

Both return BorderRadius.zero. TableBorder.lerp and TableBorder.scale build a new TableBorder from the six sides only, so a table with rounded corners loses them for the whole of an animation, for example when the table's border animates through a theme change. TableBorder.lerp(null, b, t) goes through scale, so animating a rounded border in from nothing is affected too.

Flutter version

master and stable 3.47.8.

@ChandraChaan

@ChandraChaan Thanks for the report. I was able to reproduce the issue locally. Both TableBorder.lerp(a, b, 0.5) and b.scale(0.5) return BorderRadius.zero instead of preserving the expected border radius. Routing to the team-framework for further investigation.

Sample Code

import 'package:material_ui/material_ui.dart';

void main() {
  final a = TableBorder.all(
    borderRadius: const BorderRadius.all(Radius.circular(4)),
  );

  final b = TableBorder.all(
    borderRadius: const BorderRadius.all(Radius.circular(12)),
  );

  final lerped = TableBorder.lerp(a, b, 0.5)!;
  final scaled = b.scale(0.5);
  debugPrint('lerp: ${lerped.borderRadius}');
  debugPrint('scale: ${scaled.borderRadius}');
  debugPrint('lerp from null: ${TableBorder.lerp(null, b, 0.5)!.borderRadius}');
  runApp(
    MaterialApp(
      home: Scaffold(
        appBar: AppBar(title: const Text('TableBorder Reproduction')),
        body: Padding(
          padding: const EdgeInsets.all(16),
          child: Column(
            crossAxisAlignment: CrossAxisAlignment.start,
            children: [
              Text('lerp radius: ${lerped.borderRadius}'),
              Text('Expected: BorderRadius.circular(8)'),
              const SizedBox(height: 16),
              Text('scale radius: ${scaled.borderRadius}'),
              Text('Expected: BorderRadius.circular(6)'),
              const SizedBox(height: 16),
              Text(
                'lerp from null: '
                '${TableBorder.lerp(null, b, 0.5)!.borderRadius}',
              ),
              const Text('Expected: BorderRadius.circular(6)'),
            ],
          ),
        ),
      ),
    ),
  );
}

Flutter Doctor Output

[✓] Flutter (Channel master, 3.50.0-1.0.pre-209, on macOS 27.0 26A428 darwin-arm64, locale en-IN) [2.0s]
    • Flutter version 3.50.0-1.0.pre-209 on channel master at /Users/suryakommana/develop/flutter
    • Upstream repository https://github.com/flutter/flutter.git
    • Framework revision 7b0a985e54 (4 days ago), 2026-10-23 00:20:16 +0000
    • Engine revision 7b0a985e54
    • Dart version 3.15.0 (build 3.15.0-67.0.dev)
    • DevTools version 2.61.0
    • Feature flags: enable-web, enable-linux-desktop, enable-macos-desktop, enable-windows-desktop, enable-android, enable-ios, cli-animations, enable-native-assets,
      enable-record-use, enable-swift-package-manager, omit-legacy-version-file, enable-lldb-debugging, enable-uiscene-migration, enable-riscv64, enable-hcpp

[✓] Android toolchain - develop for Android devices (Android SDK version 36.0.0) [1,436ms]
    • Android SDK at /Users/suryakommana/Library/Android/sdk
    • Emulator version 37.1.11.0 (build_id 15917651) (CL:N/A)
    • Platform android-37.0, build-tools 36.0.0
    • Java binary at: /Applications/Android Studio.app/Contents/jbr/Contents/Home/bin/java
      This is the JDK bundled with the latest Android Studio installation on this machine.
      To manually set the JDK path, use: `flutter config --jdk-dir="path/to/jdk"`.
    • Java version OpenJDK Runtime Environment (build 25.0.2+-15348964-b329.117)
    • All Android licenses accepted.

[✓] Xcode - develop for iOS and macOS (Xcode 27.1) [611ms]
    • Xcode at /Applications/Xcode.app/Contents/Developer
    • Build 27A9275
    • CocoaPods version 1.17.0

[✓] Chrome - develop for the web [3ms]
    • Chrome at /Applications/Google Chrome.app/Contents/MacOS/Google Chrome

[✓] Connected device (3 available) [8.6s]
    • iPhone 18 Pro (mobile) • D80F2104-E911-4251-BEDD-E67D9B7EBF58 • ios            • com.apple.CoreSimulator.SimRuntime.iOS-27-0 (simulator)
    • macOS (desktop)        • macos                                • darwin-arm64   • macOS 27.0 26A428 darwin-arm64
    • Chrome (web)           • chrome                               • web-javascript • Google Chrome 156.0.8078.48

[✓] Network resources [459ms]
    • All expected network resources are available.

• No issues found!

Thanks for confirming! The fix is in #195398, which is already approved. Its tests cover all three cases from your sample: lerp(a, b), scale, and lerp from/to null.

@ChandraChaan

@ChandraChaan Heads up that TableBorder is about to be deprecated in favor of TableBorderPainter, see #177102.

@justinmc

Thanks for the heads-up, @justinmc. I checked #177102: TableBorderPainter.lerp and TableBorderPainter.scale also rebuild the border from the six sides only, so they drop borderRadius the same way.

#195398 fixes TableBorder itself (it's approved), and since TableBorder stays usable through the deprecation period, I think it's still worth landing. Once #177102 is in, I'll send a follow-up that applies the same fix and tests to TableBorderPainter, unless @hm21 would rather include it in #177102.

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TableBorder.lerp and TableBorder.scale drop borderRadius #195397

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TableBorder.lerp and TableBorder.scale drop borderRadius #195397

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suryaKommana2662 commented on Oct 27, 2026

ChandraChaan commented on Oct 27, 2026

justinmc commented on Oct 27, 2026

ChandraChaan commented on Oct 27, 2026

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