Workflow building blocks

Build workflow diagrams from operations, human tasks and control-flow blocks.

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Opening the live canvas…

Choose a block from the palette, edit its label and inputs, then connect its ports. The example builds workflow drafts; it does not execute them.

Available blocks

Block	Use it for
Start / End	Mark the entry and exit of a workflow.
Operation	A registered automated task.
Human work	A task with named responses, such as approve or revise.
Wait for event	Wait for an external event.
Sleep / timer	Continue after a delay.
Decision / switch	Choose a path based on a value.
Parallel / Race / Quorum	Run branches until all, the first, or a required number finish.
Branch end	Finish one branch.
Call / Spawn / Join workflow	Run a child workflow and optionally wait for it.
Saga	Pair steps with compensating actions.
For each	Repeat a branch for each item.
Continue as new	Start another run with new input.
Query	Read a registered query.

Set it up

Register the standard blocks and attach the session to a Flutter canvas:

import 'package:vyuh_diagram_kit/vyuh_diagram_kit.dart';
import 'package:vyuh_diagram_workflow/vyuh_diagram_workflow.dart';

final registry = WorkflowAuthoringRegistry([
  WorkflowStart(),
  ...defaultWorkflowPrimitives(),
]);
final documentSession = registry.createSession(
  textLayout: FlutterDiagramTextLayoutEngine(),
);
final canvasSession = DrawingSession.fromSession(documentSession);
final canvas = DrawingCanvas(session: canvasSession);

Use registry.entries for your palette. Create a node with its registered shape type:

canvasSession.createShape(
  type: registry.entries.first.shapeType,
  worldCenter: const DiagramPoint(100, 100),
);

Unmount the canvas, then dispose canvasSession followed by documentSession. For headless authoring, use registry.createSession() without the Flutter adapter.

Add your own tasks

Add WorkflowOperation and WorkflowWork entries to the registry using your workflow engine contracts. Use WorkflowResponse to name the outcomes of human work.

The example registers Send notification and Review proposal. Expand its source for a complete registration example.

Task registration source

import 'package:json_schema_builder/json_schema_builder.dart' as json;
import 'package:vyuh_diagram_workflow/vyuh_diagram_workflow.dart';
import 'package:vyuh_workflow_engine/vyuh_workflow_runtime.dart' as runtime;

/// Example business contracts compose with the durable control primitives.
/// No handlers are installed and no execution service is created.
WorkflowAuthoringRegistry exampleWorkflowRegistry() {
  final attachment = json.Schema.object(
    properties: {'name': json.Schema.string(), 'url': json.Schema.string()},
    required: ['name', 'url'],
  );
  final request = runtime.Schema.identity<Map<String, Object?>>(
    name: 'notification-request',
    jsonSchema: json.Schema.fromMap({
      ...json.Schema.object(
        properties: {
          'recipient': json.Schema.string(),
          'message': json.Schema.string(),
          'priority': json.Schema.string(enumValues: ['normal', 'urgent']),
          'cc': json.Schema.list(items: json.Schema.string()),
          'delivery': json.Schema.object(
            properties: {'sender': json.Schema.string()},
          ),
          'attachments': json.Schema.list(
            items: json.Schema.fromMap({r'$ref': r'#/$defs/attachment'}),
          ),
        },
        required: ['recipient', 'message'],
      ).value,
      r'$defs': {'attachment': attachment.value},
    }),
  );
  final receipt = runtime.Schema.identity<Map<String, Object?>>(
    name: 'notification-receipt',
    jsonSchema: json.Schema.object(
      properties: {'messageId': json.Schema.string()},
      required: ['messageId'],
    ),
  );
  final review = runtime.Schema.identity<Map<String, Object?>>(
    name: 'review-request',
    jsonSchema: json.Schema.object(
      properties: {
        'title': json.Schema.string(),
        'summary': json.Schema.string(),
      },
      required: ['title', 'summary'],
    ),
  );
  runtime.Schema<Map<String, Object?>> response(
    String name,
    List<String> decisions,
  ) => runtime.Schema.identity<Map<String, Object?>>(
    name: name,
    jsonSchema: json.Schema.object(
      properties: {
        'decision': json.Schema.string(enumValues: decisions),
        'comment': json.Schema.string(),
      },
      required: ['decision', 'comment'],
    ),
  );
  return WorkflowAuthoringRegistry([
    WorkflowOperation<Map<String, Object?>, Map<String, Object?>, Never>(
      label: 'Send notification',
      description: 'System work: send a message and return its receipt.',
      operation: runtime.Operation(
        name: 'send-notification',
        input: request,
        output: receipt,
      ),
    ),
    WorkflowWork<Map<String, Object?>, Map<String, Object?>>(
      label: 'Review proposal',
      description: 'Human work: approve the proposal or request a revision.',
      work: runtime.Work(
        name: 'review-proposal',
        input: review,
        response: response('review-response', ['approve', 'revise']),
      ),
      responses: [
        WorkflowResponse(
          id: 'approve',
          label: 'Approve',
          payload: response('approval', ['approve']),
        ),
        WorkflowResponse(
          id: 'revise',
          label: 'Request revision',
          payload: response('revision', ['revise']),
        ),
      ],
    ),
    WorkflowStart(),
    ...defaultWorkflowPrimitives(),
  ]);
}