Default Values and Configuration Hierarchy

This guide explains how default values work in AG Charts and how to find the actual runtime defaults for any configuration option.

Why This Matters

Understanding the default value hierarchy is critical for:

• Documentation accuracy: Must document actual runtime defaults users experience
• Code reviews: Verify changes don't unintentionally alter defaults
• Testing: Write tests against realistic default behavior
• Bug reports: Understand what users see by default
• Breaking changes: Identify when theme changes affect user experience

The Three-Tier Default System

AG Charts uses a layered configuration system where each layer can override the previous one:

User Configuration
        ↓ (overrides)
Theme Template Defaults ⭐ Runtime Default
        ↓ (overrides)
Property Decorator Defaults

1. Property Decorator Defaults (Base Layer)

Location: packages/ag-charts-{community,enterprise}/src/**/*Properties.ts

Purpose: Fallback defaults when no theme is applied

Example:

// sankeySeriesProperties.ts
export class SankeySeriesNodeProperties {
    @Property
    spacing: number = 1; // Base default (rarely used)

    @Property
    alignment: 'left' | 'right' | 'center' | 'justify' = 'justify';
}

Important: These are NOT what users typically experience. They're fallback values that are usually overridden by theme templates.

2. Theme Template Defaults (Runtime Layer) ⭐

Location: packages/ag-charts-{community,enterprise}/src/**/*Module.ts

Purpose: The actual out-of-the-box defaults users experience

Example:

// sankeyModule.ts
export const SankeyModule = {
    type: 'series',
    identifier: 'sankey',
    themeTemplate: {
        series: {
            node: {
                spacing: 20, // ✅ This is the ACTUAL runtime default
                width: 10, // ✅ Overrides Properties.ts value of 1
            },
            label: {
                spacing: 10, // ✅ Overrides Properties.ts value of 1
            },
        },
    },
};

Critical: This is the layer that matters for users. When documenting defaults or testing behavior, use these values.

3. User Configuration (Override Layer)

Location: User's chart options

Purpose: Final overrides provided by the developer

Example:

const options = {
    series: [
        {
            type: 'sankey',
            node: {
                spacing: 30, // ✅ Overrides theme default of 20
            },
        },
    ],
};

Finding Defaults: Step-by-Step Process

When you need to verify the default value of a property:

Step 1: Identify the Module File

Find the module that registers the series/feature:

# For a series
find packages/ag-charts-{community,enterprise}/src/series -name "*Module.ts" | grep <seriesName>

# For Sankey series example
find packages/ag-charts-enterprise/src/series -name "*Module.ts" | grep sankey
# Result: packages/ag-charts-enterprise/src/series/sankey/sankeyModule.ts

Step 2: Check the Theme Template

Open the module file and look for the themeTemplate object:

export const SankeyModule = {
    themeTemplate: {
        series: {
            node: {
                spacing: 20, // ← Actual runtime default
                minSpacing: 0,
                width: 10,
            },
        },
    },
};

If the property exists in themeTemplate: This is the runtime default ✅

If the property is NOT in themeTemplate: Continue to Step 3

Step 3: Fallback to @Property Decorator

If the property isn't in the theme template, check the Properties class:

// sankeySeriesProperties.ts
export class SankeySeriesNodeProperties {
    @Property
    strokeWidth: number = 1; // Used as default (not overridden in theme)
}

Step 4: Verify TypeScript Comments Match

Check the TypeScript interface comments:

// sankeyOptions.ts
export interface AgSankeySeriesNodeOptions {
    /**
     * Spacing between the nodes.
     *
     * Default: `20` // ← Should match themeTemplate value
     */
    spacing?: PixelSize;
}

If the comment doesn't match the theme template: The comment is stale and needs updating.

JSDoc formatting: Default: must be its own paragraph

The Default: marker must be separated from the description prose by a blank * line inside the JSDoc block. If it sits inline with the description, the docs-site API reference renders it as body text rather than as a labelled default.

// ✅ GOOD — Default: rendered as a labelled default in the API reference
/**
 * Spacing between the nodes.
 *
 * Default: `20`
 */
spacing?: PixelSize;

// ❌ BAD — Default: swallowed into the description prose
/** Spacing between the nodes. Default: `20` */
spacing?: PixelSize;

This applies to every option in packages/ag-charts-types regardless of description length — even a one-sentence description must promote the Default: marker to its own paragraph.

Common Module Locations

Summary

Key Takeaways:

1. ⭐ Theme templates define runtime defaults - start here
2. Property decorators are fallbacks, not user-facing defaults
3. Always verify TypeScript comments match theme templates
4. Module files (*Module.ts) are the source of truth for defaults
5. Document what users actually see, not internal fallback values

Quick Workflow:

Need default? → Check *Module.ts theme → If not there, check @Property decorator → Document that value