Guide 04

The extensibility mechanisms

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Each mechanism is illustrated below with the GeneXus Work With pattern. Full, build-it guides (interfaces, invocation flow, gotchas) live in the projects' ai/ folders.

1. Custom Types — dynamic dropdowns

You implement IPatternCustomTypeSupport.getTypeEditor(id), returning an editor whose getValues(context) computes the options for a custom(<id>) property.

Work With example: the GridCustomRender custom type returns the available grid controls.

class WorkWithCustomTypeSupport implements IPatternCustomTypeSupport {
  getTypeEditor(id: string) {
    return id === 'GridCustomRender' ? new GridCustomRenderEditor() : null;
  }
}

→ Deep dive: ai/EXTENSIBILITY-CUSTOM-TYPES.md.

2. Captions — node labels

You implement IPatternEditorHelper.customShowElement(element, ctx), returning { handled, caption, icon }. Return { handled: false } for nodes you don't customize. (The optional icon lets you override a node's icon inline; for icons that ship as bundled resources use the dedicated hook in mechanism 4.)

Work With example: the Modes node shows modes (Insert, Update, ...) listing the enabled modes.

customShowElement(element) {
  if (element.elementType === 'Modes')
    return { handled: true, caption: `modes (${enabledModes(element).join(', ')})` };
  return { handled: false };
}

→ Deep dive: ai/EXTENSIBILITY-CAPTIONS.md.

3. Custom Actions — context commands

You implement IPatternEditorHelper.getCommands(element), returning serializable commands (usually subclasses of PatternEditorCommandBase). The command's exec() runs on click and may mutate the instance tree.

Work With example: "Add Filter Variable" on the FilterAttributes node.

getCommands(element) {
  return element.elementType === 'FilterAttributes'
    ? [new AddFilterVariableCommand(element).toSerializable()].filter(Boolean)
    : [];
}

→ Deep dive: ai/EXTENSIBILITY-CUSTOM-ACTIONS.md.

4. Node icons — bundled resource icons

You implement IPatternEditorHelper.getNodeIcon(element, iconName?), returning the node's icon as a self-contained resource (typically a data: URI). KB Editor resolves a node's icon in order — the caption's inline icon (mechanism 2), then the schema's Icon when it exists as a file next to the pattern, then this hook, then a built-in glyph — so returning undefined falls through to the next source.

Work With example: the pattern declares its icons as .NET assembly resources (Icon="ObjectAttribute" IconResource="…,Artech.Patterns.WorkWith"), which don't exist as files on the client's KB. The extension bundles those images under icons/ (named exactly like the schema Icon values) and returns them here, so the tree shows the real icons with no GeneXus SDK or .NET assemblies at runtime.

getNodeIcon(element, iconName) {
  if (!iconName || !/^[A-Za-z0-9_]+$/.test(iconName)) return undefined;
  const file = path.join(this.iconsDir, `${iconName}.ico`);
  return fs.existsSync(file)
    ? `data:image/x-icon;base64,${fs.readFileSync(file).toString('base64')}`
    : undefined;
}

→ Deep dive: the Work With example's WorkWithEditorHelper.getNodeIcon and its bundled icons/ folder.

Optional: Variables

If your pattern exposes context variables in embedded code, implement IPatternVariableProvider to feed KB Editor's autocomplete. → ai/EXTENSIBILITY-VARIABLES.md.

Next: C# → TypeScript workflow.

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Extensibility architecture

C# → TypeScript workflow