build a node invocation

[Ichthyostega]

As Lumiera developer,
I want to build up a Render Node Invocation exemplarily,
in order to achieve integration of the existing code and identify missing parts.

Integration driver task

The purpose of this test work is to establish a nucleus to seed the integration effort. There is a lot of existing code at various levels of quality and completeness, which must be connected to the external counterparts prepared recently

• the JobTicket
• a Planning Process driven incrementally as part of a Calculation Stream
• a JobFunctor that can be invoked from the Scheduler
• a DataSink for output

Acceptance Criteria

• several ProcNode instances can be created, ad-hoc, in a test setting
• these nodes can be connected
• the »scaffolding« necessary for an actual invocation can be attached
• an invocation sequence can be triggered (»pull«)

[Ichthyostega <prg@…>]

In 9f348e6/Lumiera:

Invocation: able to build and invoke a simple Render Node (see: #1367)

This is a Milestone for the Render Engine integration effort

After various rounds of prototyping and refactoring,
the Render Node builder and invocation code is now able to

• bind a simple function
• handle arbitrary input / output and parameter types
• invoke a Render Node configured with this function

[Ichthyostega]

The further prototyping for #1371 has uncovered an API mismatch between the Buffer Provider protocol and the Output Slot (#1395). While we can now invoke a chain of Render Nodes stand-alone, this mismatch must be mitigated to allow integration into a Render Job — because the emit() call issued from within the render processing must be forwarded properly to the Output Slot.

And, in addition, we obviously need a (trivial, dummy-style) BufferProvider implementation (#1396).

[Undercover Agent]

Migration MasterTickets ⟼ Subtickets-plugin

[Ichthyostega]

Add subticket #1410 (clean-up BufferProvider base implementation).

[Ichthyostega]

Attach to parent #1417 (unwind from Render Node pull).