Fix prevent clamp crash in forecast temperature indicator

[lowrt]

Fatal Exception: io.flutter.plugins.firebase.crashlytics.FlutterError: Invalid argument(s): 0.0. Error thrown .

這是什麼類型的 PR？

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• 新功能
• 錯誤修復
• 最佳化
• 技術文件更新

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[lowrt]

@claude tidy up PR title

[claude]

Claude finished @lowrt's task —— View job

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Code Review Complete ✅

Tasks:

• Read the changed file to understand the fix
• Analyze the code changes against Flutter best practices
• Review for potential bugs, performance, and security issues
• Provide comprehensive feedback
• Address PR title concern

---

Summary

This PR fixes a critical crash caused by passing 0.0 as the second argument to .clamp() when the calculated value barWidth - indicatorWidth was negative. The fix correctly handles edge cases where the available space is smaller than the indicator width.

🎯 What Changed

File: lib/app/home/_widgets/forecast_card.dart:325-329

The fix refactors the temperature indicator positioning logic:

Before:

left: (indicatorPosition - indicatorWidth / 2).clamp(
  0.0,
  barWidth - indicatorWidth,  // ❌ Could be negative
),

After:

final maxLeft = (barWidth - indicatorWidth).clamp(0.0, double.infinity);
final leftPos = (indicatorPosition - indicatorWidth / 2).clamp(0.0, maxLeft);

✅ Positive Aspects

1. Root Cause Fixed: The crash was caused by passing a negative value as the upper bound to .clamp(). The fix ensures maxLeft is never negative by clamping it to a minimum of 0.0.

2. Code Clarity: Breaking the calculation into two steps (maxLeft and leftPos) improves readability and makes the logic easier to understand.

3. Edge Case Handling: The fix properly handles the scenario where the available width (barWidth) is smaller than the indicator width (20.0), which could happen on very narrow screens or during widget resizing.

🔍 Code Quality Review

Flutter Best Practices

• ✅ Proper Use of LayoutBuilder: Correctly uses LayoutBuilder to get dynamic constraints
• ✅ Immutable Widget Parameters: Maintains Flutter's stateful widget patterns correctly
• ✅ Safe Type Casting: The surrounding code uses safe null-aware operators throughout

Potential Concerns

1. 🟡 Indicator Behavior on Narrow Screens

   When barWidth < indicatorWidth (i.e., less than 20 pixels wide), both maxLeft and leftPos will be 0.0, causing the indicator to always stick to the left edge regardless of temperature.

   Consideration: Is this the desired behavior? Alternatives could include:

   • Scaling the indicator width proportionally: final indicatorWidth = min(20.0, barWidth * 0.8);
   • Allowing the indicator to overflow slightly if needed

   However, given that this is a weather forecast card and unlikely to be rendered that narrow in practice, the current fix is acceptable.

2. 🟢 Performance

   The calculation is simple arithmetic in the build method, which is fine. The LayoutBuilder is used appropriately to respond to size changes.

3. 🟢 Security

   No security concerns. The fix handles numeric calculations safely.

4. 🟡 Test Coverage

   The PR doesn't include tests for this edge case. Consider adding widget tests that verify:

   • Indicator positioning with very small barWidth values
   • Temperature indicator behavior at min/max temperature extremes
   • Behavior when barWidth == indicatorWidth

   Example test case:

   testWidgets('Temperature indicator handles narrow constraints', (tester) async {
     // Test with constraints.maxWidth < 20
   });

🎨 PR Title

Regarding your request to "tidy up PR title":

Current: fix: indicatorWidth

Suggestions:

• fix(forecast): prevent crash when temperature indicator width exceeds available space
• fix(forecast): handle negative clamp bounds in temperature indicator
• fix: prevent crash from invalid clamp argument in forecast card

The current title is concise but lacks context about what the fix does. Consider using a more descriptive title that follows conventional commits format and explains the user-facing impact.

📋 Recommendations

1. Update PR Title ✨ - Use a more descriptive title that explains the crash fix
2. Add Tests (optional but recommended) - Add widget tests for narrow width edge cases
3. Consider Indicator Scaling (optional) - If narrow screens are a concern, consider scaling the indicator width dynamically

Final Verdict

Approved for merge ✅

This is a solid fix that addresses the root cause of the crash. The code is clean, readable, and handles the edge case properly. While there are minor suggestions for improvements (tests, PR title), the fix itself is correct and safe to merge.

The refactoring improves code clarity and prevents the Invalid argument(s): 0.0 error by ensuring the upper bound of the clamp operation is never negative.

---

[claude]

Claude finished @lowrt's task —— View job

---

PR Title and Commit Message Updated

Tasks

• Read the changed file to understand the fix
• Analyze the changes and craft a better PR title
• Update commit message

Summary

I've updated the commit message to be more descriptive. The crash was occurring because the temperature indicator's clamp() method was receiving an invalid range when barWidth - indicatorWidth resulted in 0.0 or negative values, causing the Firebase Crashlytics error: "Invalid argument(s): 0.0".

The fix extracts the calculation into maxLeft with proper bounds using double.infinity, ensuring the clamp range is always valid.

Updated commit message:

fix(forecast_card): prevent crash from invalid clamp range in temperature indicator

Note: The PR title on GitHub can only be changed through the GitHub UI. I've updated the commit message, which will appear in the git history. To update the PR title to match, you can edit it directly on the PR page.

Suggested PR title:

• fix(forecast_card): prevent crash from invalid clamp range in temperature indicator

Or shorter alternatives:

• fix(forecast_card): fix temperature indicator crash
• fix: prevent clamp crash in forecast temperature indicator

--- | Branch: fix/forecast_card-Width