structured_log_flutter

Headless log-viewer core for structured_log — a bounded in-memory buffer and a filterable controller for building a live, in-app log viewer in Flutter. No Material, Cupertino, or any other design-system dependency: this package renders nothing itself, so any UI skin can be built on top of it — structured_log_material, structured_log_fluent, and structured_log_cupertino all build on it.

Status: published on pub.dev (0.1.0). structured_log_material, structured_log_fluent, and structured_log_cupertino all depend on it as a regular hosted dependency; within this monorepo, melos bootstrap resolves it to a path dependency instead.

Features

• LogBuffer — a fixed-capacity ring buffer that plugs directly into structured_log as an OutputFunction/LogSink.output
• Live updates — LogBuffer.entries is a ValueListenable, so a widget can rebuild on every new entry without polling
• LogViewerController — a ChangeNotifier with level/category/search filtering, pause/resume, and clearing, all applied on top of a LogBuffer
• logLevelColor(LogLevel level, Brightness brightness) — the canonical LogLevel indicator color, shared by every skin built on this package so the palette can’t drift between them
• Zero design-system dependency — only dart:ui, package:flutter/foundation.dart, and structured_log

Installation

dependencies:
  structured_log_flutter: ^0.1.0

Within this monorepo, melos bootstrap resolves it to a path dependency instead:

dependencies:
  structured_log_flutter:
    path: ../structured_log_flutter

Quick Start

import 'package:structured_log/structured_log.dart';
import 'package:structured_log_flutter/structured_log_flutter.dart';

final buffer = LogBuffer(capacity: 500);
final controller = LogViewerController(buffer);

StructlogConfiguration.configure(sinks: [
  LogSink(name: 'console', output: coloredConsoleOutput),
  LogSink(name: 'viewer', output: buffer.capture),
]);

getLogger().info('user_login', context: {'user_id': 42});

controller.levelFilter = LogLevel.warning; // only warning and above
controller.searchQuery = 'login';          // further narrowed by text
print(controller.visibleEntries);

API Reference

LogBuffer

Member	Description
LogBuffer({int capacity = 500})	Creates an empty buffer; oldest entry evicted once capacity is exceeded
capture(Map<String, dynamic> entry, LogLevel level)	Matches OutputFunction’s signature — pass it directly as a sink’s output
entries	ValueListenable<List<Map<String, dynamic>>>, oldest first
clear()	Empties the buffer and notifies entries’ listeners

LogViewerController

A ChangeNotifier wrapping a LogBuffer:

Member	Description
levelFilter (LogLevel?)	Minimum level a visible entry must have; null = no restriction
categoryFilter (String?)	Exact category context value required; null = no restriction
searchQuery (String)	Case-insensitive substring match against event and every other context value (level/timestamp excluded)
paused (bool)	While true, visibleEntries stays frozen at the entries visible when paused, even as buffer keeps capturing
visibleEntries	The buffer’s entries, filtered by the three properties above
clear()	Clears buffer (and any frozen snapshot) and notifies listeners
dispose()	Detaches from buffer.entries — call when the controller is no longer needed

logLevelOf(Map<String, dynamic> entry)

Parses an entry’s level context key back into a LogLevel, matching by name — returns null if missing or unrecognized. Exposed as a standalone function so a UI skin (like structured_log_material) doesn’t need to reimplement this parsing.

logLevelColor(LogLevel level, Brightness brightness)

The single source of truth for LogLevel indicator colors, used by every skin’s list row, detail view, and badges. Lives here (not in any one skin) because Color/Brightness aren’t tied to Material, Cupertino, or Fluent — this table is genuinely design-system-neutral, unlike the widgets built on top of it.

Building a UI Skin

structured_log_flutter intentionally renders nothing — wire a LogViewerController up to whatever widgets you like, listening to it as any other ChangeNotifier (AnimatedBuilder, ListenableBuilder, etc.) and reading visibleEntries for what to display. See structured_log_material, structured_log_fluent, and structured_log_cupertino for complete reference implementations (list, expanded-entry detail, empty states) on Material 3, Fluent UI, and Cupertino respectively.

License

MIT