version: "1.0.1" name: "panel-log" description: "Deep Log panel knowledge: react-window VariableSizeList virtualization, dynamic measured row heights, autoscroll/tail behavior, multi-format log normalization, and level/text filtering."

Panel Log Skill

A high-performance log viewer with virtualized rendering and filtering.

Structure

panels/Log/
├── index.tsx          # main panel, filter state, topic selection, settings
├── LogList.tsx        # react-window VariableSizeList, dynamic heights, autoscroll
├── filterMessages.ts  # level + text filtering
└── conversion.tsx     # normalize ROS1/ROS2/Foxglove log formats

Virtualized Rendering (react-window)

<VariableSizeList
  height={containerHeight}
  itemCount={filteredMessages.length}
  itemSize={getItemSize}   // dynamic: cached height per row
  ref={listRef}
>
  {LogRow}
</VariableSizeList>

Dynamic Row Heights

• Each entry can differ (multi-line messages, stack traces)
• Heights are measured after first render and cached
• resetAfterIndex() is called when content changes (recalculates from that point)
• Cache is invalidated on resize or filter change

Autoscroll (tail)

• At bottom → auto-scroll to new messages
• Scrolled up → autoscroll disabled (reading history)
• Scroll-to-bottom button re-enables it

Message Normalization (conversion.tsx)

Unifies multiple formats into one structure:

interface NormalizedLogMessage {
  level: LogLevel;   // DEBUG, INFO, WARN, ERROR, FATAL
  message: string;
  name?: string;     // logger name
  timestamp: Time;
  file?: string;
  line?: number;
}

Supported inputs: rosgraph_msgs/Log (ROS 1), rcl_interfaces/msg/Log (ROS 2), foxglove.Log.

Filtering (filterMessages.ts)

function filterMessages(
  messages: NormalizedLogMessage[],
  minLevel: LogLevel,
  searchTerm: string,
): NormalizedLogMessage[];

• Level filter: messages at or above the selected level
• Text search: case-insensitive substring match (no regex by default)
• Runs on every new batch — must stay fast for 10k+ messages

Performance Notes

• Only visible rows are rendered (react-window)
• Measured heights are cached to avoid layout thrashing
• Messages are accumulated and filtered in batches (250ms debounce)
• scrollToItem is only called when actually at the bottom

Key Files

• packages/suite-base/src/panels/Log/index.tsx
• packages/suite-base/src/panels/Log/LogList.tsx
• packages/suite-base/src/panels/Log/filterMessages.ts
• packages/suite-base/src/panels/Log/conversion.tsx