Theory of Operation

Interactive manipulator

Horizon’s primary interface is the so-called “Interactive manipulator” (imp). It’s the unified editor for symbols, schematics, padstacks, packages and boards.


The canvas renders objects such as symbols, packages or tracks. The output of the rendering are line segments and triangles that get uploaded to the GPU for drawing. For rendering to to non-OpenGL targets, the canvas provides hooks to get more information on what’s being rendered. So far, this is used by the gerber exporter, 3D preview and DRC.


Since some documents such as symbols and schematics contain the same type of object (e.g. texts) and schematic and netlist need to be modified in-sync, some encapsulation has to take place. The core can be considered the glue between the document, the canvas and the tools.


For each action the user can do, there’s a tool. Once started, a tool receives keyboard and mouse input and modifies the document accordingly by means of the core. When needed, a tool may bring up additional dialogs for requesting information from the user.

Property editor

Low-complexity adjustments such as line width don’t warrant their own tool, that’s why the the core provides a property interface. The property editor’s widgets are automatically generated from the object’s description.