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RegisterMessageConverterArgsTopic

type RegisterMessageConverterArgsTopic = object;

This type represents the arguments you pass to ExtensionContext.registerMessageConverter when you want to register a topic message converter.

Properties​

type​

type: "topic";

inputTopics​

inputTopics: string[];

outputTopic​

outputTopic: string;

outputSchemaName​

outputSchemaName: string;

Name of the schema for messages output by the converter.

If you output well-known messages like a foxglove CompressedImage then your schema name would be foxglove.CompressedImage.

If you are creating a new custom schema you can assign any name. Avoid picking an existing name if your data uses a different schema.

NOTE: For ROS users, we also support names like sensor_msgs/msg/CompressedImage. See the supported messages documentation for each panel to learn what kinds of schemas it can display.

outputSchemaDescription?​

optional outputSchemaDescription: MessageSchemaDescription;

Describes the structure of the output messages produced by this converter.

This optional field allows Foxglove to understand the structure of your messages, enabling features like autocompletion for message path selection.

The schema can include:

  • Primitive types: "string", "number", "bool", "byte"
  • Arrays of primitives: ["string"], ["number"], ["bool"], ["byte"]
  • Nested objects with their own field definitions
  • Arrays of objects (each element having the same structure)

Example​

schemaDescription: {
  // Simple fields
  timestamp: "number",
  label: "string",
  enabled: "bool",
  flags: "byte",

  // Array of primitives
  values: ["number"],
  names: ["string"],
  options: ["bool"],
  data: ["byte"],

  // Nested object
  position: {
    x: "number",
    y: "number",
    z: "number"
  },

  // Array of objects
  landmarks: [{
    id: "string",
    position: {
      x: "number",
      y: "number"
    }
  }]
}

schemaName?​

optional schemaName: string;

Deprecated​

use outputSchemaName instead

schemaDescription?​

optional schemaDescription: MessageSchemaDescription;

Deprecated​

use outputSchemaDescription instead

create()​

create: () => TopicConverterReturnType;

The create function initializes the converter. It is called by the app to create the converter when some panel subscribes to the output topic.

create: () => {
  return (msgEvent: MessageEvent) => {
    const msg = msgEvent.message as MySignal;
    return { value: Math.abs(msg.acceleration) };
  };
},

Returns​

TopicConverterReturnType

A function that is called with a MessageEvent for every input message. It performs any computation and returns a new message(s) matching the schema description. The function can optionally return undefined to skip producing message(s) for the given input.