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Case Study: Picasso — Alternative Input Architecture

Context

Picasso expanded the Paradigm surgical platform to support hands-free interaction via a footswitch. The objective was not simply to integrate a new device, but to evolve the system’s interaction model without compromising architectural clarity or regulatory stability.

I led the technical evaluation and architectural design of the input integration.

Problem Framing

The selected footswitch presented as a keyboard HID device. While this minimized driver complexity, it surfaced a structural issue: Windows aggregates keyboard devices into a single logical input stream. Without explicit differentiation, the application could not distinguish footswitch input from standard keyboard input.

The architectural decision was whether to rely on OS-level abstractions and introduce brittle filtering logic, or to take ownership of device-level differentiation.

I chose to move below the abstraction boundary.

Architectural Strategy

We implemented input monitoring using Windows RawInput to obtain device-level granularity and explicitly separate input sources.

Because Windows allows only a single RawInput handler per process, the input system was designed as a centralized capability rather than a feature-specific implementation.

The architecture introduced:

  • A centralized RawInput manager responsible for device discovery and classification

  • Strategy-based input handlers for device-specific behavior

  • Interface abstractions aligned with the Dependency Inversion Principle

  • A configurable registration model enabling future alternative input devices

This ensured that hardware concerns remained isolated from application behavior and that additional devices could be introduced without structural refactoring.

Input events were then routed through a dedicated Input System model to active ViewModels, preserving MVVM boundaries and preventing device logic from leaking into presentation code.

The guiding principle was clear separation of concerns under OS constraint.

Interaction Design Under Constraint

Hands-free control in a surgical setting requires confidence without distraction. We introduced contextual UI affordances and unobtrusive audio feedback to confirm invocation and outcome without shifting surgeon focus.

The system needed to communicate state changes clearly while remaining peripheral.

Impact

Picasso established a generalized input framework rather than a device-specific integration. It enabled sterile interaction, preserved architectural integrity, and created a scalable foundation for future alternative input mechanisms.

More importantly, it demonstrated that hardware integration could be treated as an extensible platform capability rather than a one-off feature.

Lessons Learned

This effort reinforced that platform capabilities should be designed, not bolted on. Operating system abstractions are useful until they obscure important distinctions, and when that happens it is often worth taking ownership at a lower boundary. By centralizing input detection and designing for extensibility from the first device, we avoided structural rework later. Just as importantly, integrating hardware into a surgical workflow requires as much attention to feedback and confidence as to technical correctness.