Symbol Libraries

Where symbols come from

While you draw, symbols are taken from the application’s system library (the shipped set listed in Placing Symbols). Each symbol is an SVG <g> element that carries its own metadata in data-* attributes:

<g id="R"
   data-prefix="R"
   data-nodes="pos neg"
   data-model="R"
   data-params="value dcvar dcvarlot noisetemp noiseflow"
   data-description="Resistor (nonzero resistance)"
   data-info="https://www.slicap.org/syntax/devices.html#r-resistor">
   ...artwork and pin markers...
</g>

The editor reads everything it needs from these attributes — there is no separate table to keep in sync.

• data-prefix — the device letter / reference-designator prefix.

• data-nodes — the node names, in the order the netlister expects. A pin’s position is given by a <circle class="node" data-node="..."> marker.

• data-model — the SLiCAP model name.

• data-params — the parameters the user may set.

• data-description / data-info — the text and link shown in the Properties dialog.

The symbol’s outline extent (used for selection) is computed from its geometry, so symbols never need a hand-maintained bounding box.

Frozen copies travel with the schematic

When you save, the symbols the schematic uses are copied into its <name>.symbols sidecar (see Project Files). When you open a schematic, those frozen copies are loaded on top of the system library, so the drawing always renders with the symbols it was created with — even if the shipped symbols change later.

Custom and overriding symbols

Because a frozen symbol overrides the system symbol of the same name, you can customise how a device looks. For example, you can draw the nullor N as an operational-amplifier triangle, freeze it into a schematic’s .symbols, and that schematic will use your version while everything else keeps the standard IEC symbol.