Plugins were initially developed for the 3D model viewer to make it possible to support more types of 3D models without requiring major changes to the KiCad source for each new model type supported. The plugin framework was later generalized so that in the future developers can create different classes of plugins. Currently only 3D plugins are implemented within KiCad but it is envisioned that a PCB plugin will eventually be developed to make it possible for users to implement data Importers and Exporters.

Implementing a Plugin Class requires creating code within the KiCad source tree which manages the loading of plugin code. Within the KiCad source tree, the file declares the base class for all plugin loaders. This class declares the most basic functions which we would expect to find in any KiCad plugin (boilerplate code) and its implementation provides basic checks on version compatibility between the plugin loader and the available plugins. The header declares a loader for the 3D Plugin Class. The loader is responsible for loading a given plugin and making its functions available to KiCad. Each instance of a plugin loader represents an actual plugin implementation and acts as a transparent bridge between KiCad and the plugin’s features. The loader is not the only code required within KiCad to support plugins: we also need code to discover the plugins and code to invoke the functions of the plugins via the plugin loader. In the case of the 3D plugins the discovery and invocation functions are all contained within the S3D_CACHE class.

The header declares the generic functions required of all KiCad plugins; these functions identify the Plugin Class, provide the name of the specific plugin, provide version information for the Plugin Class API, provide version information for the specific plugin, and provide a basic version compatibility check on the Plugin Class API. In brief, these functions are:

Plugin Class: PLUGIN_3D

The functions which the user must implement are as follows: