diy-layout-creator/diylc/.claude/skills/add-component/SKILL.md

name, description

name	description
add-component	Add a new component type to the DIYLC library, or substantially modify an existing one. Use when asked to create a new part (resistor variant, board, jack, switch, pickup, symbol, shape), add editable properties to a component, change how a component draws or reports connectivity, or make a component rotatable/mirrorable.

Adding a component to DIYLC

Components live in diylc-library/src/main/java/org/diylc/components/. They are discovered at runtime by Reflections scanning org.diylc — there is no registry to update. A class becomes a component by carrying @ComponentDescriptor and implementing IDIYComponent (in practice, by extending one of the abstract bases).

Before writing anything

1. Find the closest existing component and read it end to end. A new axial part follows passive/Resistor.java; a new board follows boards/VeroBoard.java; a new schematic symbol follows AbstractSchematicLeadedSymbol subclasses; a new jack follows electromechanical/. The new class should read like a sibling of that file.
2. Ask whether it is really a new class. If the request is a revision or size variant of something that already exists, prefer adding a Version (or similar enum) property to the existing class over creating a parallel class. That keeps old project files loading and keeps the toolbox from sprawling.
3. Pick the right package — passive, semiconductors, electromechanical, boards, guitar, tube, chassis, shapes, smd, connectivity, misc, autocreate. The package should match the category in the descriptor.

Choosing a base class

Base	Use for
AbstractComponent<T>	Anything that fits nothing else
AbstractLabeledComponent<T>	Adds name/value label rendering
AbstractTransparentComponent<T>	Anything with an alpha/transparency property
AbstractLeadedComponent<T>	Two-lead axial parts drawn between two points; implement getDefaultLength(), getDefaultWidth(), getBodyShape()
AbstractRadialComponent<T>	Radial (two leads out the same side) parts
AbstractCurvedComponent<T>	Curves and traces defined by control points
AbstractAngledComponent<T>	Parts placed by point and angle
AbstractBoard / AbstractProtoBoard / AbstractVeroBoard	Boards
AbstractMultiPartComponent<T>	Components made of several independently drawn sections
Abstract3LegSymbol, AbstractDiodeSymbol, AbstractTubeSymbol, AbstractGuitarPickup, AbstractShape	The obvious specialisations

Extend the most specific base that fits. Do not reimplement behaviour a base already provides.

The class

/* ... GPL header copied verbatim from HEADER.txt ... */
package org.diylc.components.passive;

import ...                                  // java.*, then third-party, then org.diylc.*

@ComponentDescriptor(name = "My Part", author = "Branislav Stojkovic", category = "Passive",
    creationMethod = CreationMethod.POINT_BY_POINT, instanceNamePrefix = "X",
    description = "Short sentence shown in the toolbox tooltip", zOrder = IDIYComponent.COMPONENT,
    transformer = SimpleComponentTransformer.class, enableCache = true)
public class MyPart extends AbstractLeadedComponent<Resistance> {

  private static final long serialVersionUID = 1L;

  public static Size DEFAULT_WIDTH = new Size(1d / 2, SizeUnit.in);
  public static Color BODY_COLOR = Color.decode("#82CFFD");

  private Resistance value = null;

  public MyPart() {
    super();
    this.bodyColor = BODY_COLOR;
  }

  @EditableProperty(validatorClass = PositiveMeasureValidator.class)
  public Resistance getValue() {
    return value;
  }

  public void setValue(Resistance value) {
    this.value = value;
  }

  @Override
  public void drawIcon(Graphics2D g2d, int width, int height) { ... }
}

Requirements the framework enforces:

• No-argument public constructor, and the class must be serializable with a private static final long serialVersionUID = 1L;.
• @ComponentDescriptor needs name, description, category, author, instanceNamePrefix and zOrder at minimum. Set enableCache = true for anything whose drawing is expensive and does not depend on neighbouring components.
• Appearance constants are public static and deliberately not final, so they can be overridden at runtime. Follow that.

Editable properties

• Annotate the getter with @EditableProperty; a matching setXYZ must exist. The property name comes from the getter unless you pass name.
• Use sortOrder when the order in the editor matters, defaultable = false for properties that must not be remembered as a user default, and validatorClass (e.g. PositiveMeasureValidator, PositiveNonZeroMeasureValidator) where a raw value would be invalid.
• Use the measure types from org.diylc.core.measures (Size, Resistance, Capacitance, Voltage, Power, Percentage) rather than raw numbers — they carry units and format themselves.
• For a runtime-computed list of allowed values, add @DynamicList(availableValueFunction = "getXyz") alongside @EditableProperty. (The additionalOptions example in EditableProperty's own Javadoc is stale — that attribute no longer exists.)
• Override getValueForDisplay() when the canvas label should combine several properties.

Drawing

draw(Graphics2D, ComponentState, boolean outlineMode, Project, IDrawingObserver) runs on every repaint, for every instance. Treat it as a hot path.

• Fetch strokes from ObjectCache.getInstance().fetchBasicStroke(w), fetchZoomableStroke(w) or fetchStroke(w, dash, phase, cap). Do not allocate new BasicStroke(...) in draw().
• Honour outlineMode and every ComponentState (NORMAL, SELECTED, DRAGGING) the way the neighbouring components do.
• drawIcon(g2d, width, height) is a separate, hand-drawn miniature for the toolbox — it is not a scaled call into draw().

Connectivity

If the component conducts, wrap the conductive drawing in drawingObserver.startTrackingContinuityArea(true) / stopTrackingContinuityArea(), exactly as the comparable component does. Getting this wrong silently corrupts continuity checks and the netlist without any visible rendering difference. startTracking() / stopTracking() control whether drawing contributes to the component's clickable area.

Also implement, where relevant:

• getControlPointCount(), getControlPoint(int), setControlPoint(Point2D, int), isControlPointSticky(int), getControlPointNodeName(int) — the connection points.
• getInternalLinkName(int, int) and getSectionNames(int) — internal conduction between points, needed by the netlist and analyzers.
• IGerberComponentSimple or IGerberComponentCustom if the part should appear in Gerber output.

Rotation and mirroring

These live in an IComponentTransformer under diylc-library/src/main/java/org/diylc/components/transform/, referenced from the transformer attribute of @ComponentDescriptor — never inside the component itself. Reuse SimpleComponentTransformer or an existing transformer where the behaviour matches; write a new one only when the part rotates or mirrors differently from everything that exists.

Datasheets and variants

If the part has a catalogue of real-world values and sizes, set enableDatasheet = true and datasheetCreationStepCount, and add the file under diylc-library/src/main/resources/datasheets/. Follow the format of an existing .datasheet file and add a spot-check to DatasheetServiceTest.

Backward compatibility

Once a component ships, its serialized shape is a contract:

• Never rename, remove, or retype a serialized field, and never rename or move the class.
• To replace a property, keep the old field, mark the old accessors @Deprecated, add the new field, and migrate lazily in the new getter — see AbstractTransparentComponent.getAlpha(), Resistor.getPowerNew(), AbstractFilmCapacitor.getVoltageNew().
• Fields added later arrive as null from old files; default them in the getter, not the constructor.

Verify

mvn -q -pl diylc-library -am test

Then state plainly that the component still needs a visual check in the running app — automated tests do not cover component appearance. Offer a regression-suite run (see the regression-test skill) for any change to an existing component's drawing or serialization.