app-flutter/lib/widgets/telltale.dart

// An on/off lamp in the boxed pattern (lib/widgets/stat_box.dart): the label is the
// lamp. Takes a [Reading] (lib/reading.dart) so missing and stale draw as they do elsewhere.

import 'package:flutter/material.dart';

import '../reading.dart';
import '../theme/palette.dart';

/// An on/off lamp in the boxed pattern: the label is the lamp. Lit in foreground
/// (alarm when [warn]), dark in subdued; missing shows as a dash.
class Telltale extends StatelessWidget {
  const Telltale({
    super.key,
    required this.label,
    required this.reading,
    this.icon,
    this.warn = false,
    this.flex = 1,
  });

  final String label;

  /// Drawn instead of the label when set. Glyphs like ◀ ▶ come out as emoji on Android.
  final IconData? icon;
  final Reading reading;
  final bool warn;
  final int flex;

  @override
  Widget build(BuildContext context) {
    final p = AppTheme.of(context);
    final missing = reading.value == null;
    final lit = reading.on && !reading.dim;
    final color = lit
        ? (warn ? p.alarm : p.foreground)
        : p.subdued.withValues(alpha: missing ? 0.35 : 0.6);
    return Expanded(
      flex: flex,
      child: LayoutBuilder(
        builder: (context, c) {
          final size = c.maxHeight * 0.3;
          if (icon != null && !missing) {
            return Center(
              child: Icon(
                icon,
                size: c.maxHeight * 0.7,
                color: color,
                semanticLabel: label,
              ),
            );
          }
          return Center(
            child: FittedBox(
              fit: BoxFit.scaleDown,
              child: Text(
                missing ? '—' : label,
                maxLines: 1,
                style: TextStyle(
                  fontFamily: hudFont,
                  fontSize: size,
                  fontWeight: lit ? FontWeight.w700 : FontWeight.w400,
                  color: color,
                  letterSpacing: 1,
                ),
              ),
            ),
          );
        },
      ),
    );
  }
}