In this article, we will explore how a custom tool developed with CornerstoneTools works, examining the internal mechanisms that govern callbacks, events, and state management. To make everything more concrete, we will use the TPA (Tibial Plateau Angle) as a practical case study—an especially interesting example because it requires a multi-step interaction flow and logic that is more complex than standard tools. Through this example, we will understand how to design and control each phase of a tool’s lifecycle, from the user’s initial input to the final rendering.
