Custom Business Endpoint

By default, the Blender side uses DefaultBusinessEndpoint to process business_request, emit business_event, and return business_response.

What the default endpoint supports

DefaultBusinessEndpoint carries the built-in Blender data bridge and handles these names:

• rna.list
• rna.get
• rna.set
• rna.describe
• rna.call
• ops.poll
• ops.call
• watch.subscribe
• watch.unsubscribe
• watch.read

Watch invalidation is delivered as the business_event named watch.dirty.

Every business_request, business_response, and business_event now carries explicit version fields:

• protocolVersion
• schemaVersion

Current defaults are protocolVersion = 1 and schemaVersion = 1.

On the C# side, the current BlenderApi surface for Rna, Ops, and Observe depends on these default business names.

If the Blender side replaces the endpoint with a custom one and does not keep these names compatible, the built-in BlenderApi can no longer be used directly.

Interface contract

Implement BusinessEndpoint with one entry point:

class BusinessEndpoint:
    def invoke(self, request):
        raise NotImplementedError

request is a BusinessRequest, and the return value is a BusinessResponse.

BusinessRequest.response(...) fills the current protocol and schema versions automatically, so simple custom handlers do not need to repeat them manually.

Minimal custom example

from .core import (
    BusinessEndpoint,
    BusinessRequest,
    BusinessError,
    BridgeConfig,
    BridgeController,
)


class MyBusinessEndpoint(BusinessEndpoint):
    def invoke(self, request):
        if request.name == "ping":
            return BusinessRequest.response(
                reply_to=request.message_id,
                payload={"pong": True},
            )

        return BusinessRequest.response(
            reply_to=request.message_id,
            ok=False,
            error=BusinessError(
                code="unsupported_business_request",
                message=f"Unsupported business request: {request.name}",
            ),
        )


controller = BridgeController(
    BridgeConfig(executable_path="C:/path/to/YourAvaloniaApp.exe"),
    business_endpoint=MyBusinessEndpoint(),
)

Current limitation

• With DefaultBusinessEndpoint, the built-in BlenderApi works directly
• If you replace it with a custom endpoint, the built-in BlenderApi stops working unless the custom endpoint keeps rna.*, ops.*, and watch.* compatible
• When only adding a few app-specific commands, keep DefaultBusinessEndpoint and extend on top of it