api hookmanager

Blacksmith Hook Manager API

Audience: external module developers.

This document covers the Hook Manager API for registering and managing FoundryVTT hooks through Coffee Pub Blacksmith. For general integration setup, see api-core.md.

Audience: Developers integrating with Blacksmith and using the Hook Manager for event handling.

Overview

The Hook Manager provides centralized hook management with:

Priority-based execution (1=Critical, 2=High, 3=Normal, 4=Low, 5=Lowest)
Context-based cleanup for batch operations
Throttle/debounce support for performance optimization
Dedupe protection to prevent duplicate registrations
Automatic cleanup for "once" hooks

Access

// Direct access - no await needed once Blacksmith is ready
const hookManager = BlacksmithHookManager;
BlacksmithHookManager.registerHook(...)

Core API

Register a Hook

const callbackId = BlacksmithHookManager.registerHook({
    name: 'hookName',                    // Required: FoundryVTT hook name
    description: 'Description',           // Optional: Human-readable description
    context: 'context-name',             // Optional: Batch cleanup identifier
    priority: 3,                         // Optional: 1-5, default: 3
    key: 'uniqueKey',                    // Optional: Dedupe protection
    options: {                            // Optional: Performance options — see caveats below.
        once: true,                       // Auto-cleanup after first execution
        throttleMs: 50                    // Max once per 50ms
        // debounceMs: 300                // Wait 300ms after last call — NOT with throttleMs or once
    },
    callback: (args) => { /* logic */ }   // Required: Your callback function - ALWAYS LAST
});

The three options are not freely combinable — do not set once, throttleMs, and debounceMs all at once. Two combinations misbehave silently:

throttleMs + debounceMs — throttleMs wins and debounceMs is silently discarded (the implementation is if (throttleMs) … else if (debounceMs)).
once + debounceMs — your callback never runs. Debounce only schedules the work; once then removes the callback the moment the hook fires, and removal clears the pending timer before it elapses. You get a valid callback id, no error, and silence.

Pick at most one of throttleMs / debounceMs, and don't pair debounceMs with once. The code does not warn about either combination.

Parameter Order (Recommended)

For readability and consistency, use this order:

name (required)
description (optional)
context (optional)
priority (optional)
key (optional)
canCancel (optional)
options (optional)
callback (required) - ALWAYS LAST for readability

What We Support

Required: name, callback
Optional: description, priority, options, key, context, canCancel
Options: once, throttleMs, debounceMs
Performance: Throttling and debouncing work as documented
Cleanup: once: true auto-removes hooks after first execution
Dedupe: key prevents duplicate registrations
Batch cleanup: context enables group removal
Cancellation: opt-in via canCancel -- see below

Cancellation (`canCancel`)

A callback's return value is ignored unless the registration declared canCancel: true. Returning false from an ordinary callback does nothing.

BlacksmithHookManager.registerHook({
    name: 'preCreateItem',
    description: 'Block items the vault refuses',
    context: 'my-module',
    canCancel: true,                       // top level, not inside `options`
    callback: (item) => {
        if (isForbidden(item)) return false;   // cancels the creation
    }
});

This is opt-in because every callback registered against one hook name shares a single Foundry handler. An undeclared false would speak for all of them, and the dangerous case is not a deliberate veto -- it is an ordinary callback whose natural return value happens to be a boolean. callback: (doc) => this.tracked.has(doc.id) is a normal thing to write, and on a pre* hook it would block the operation world-wide, for every module, with nothing logged.

Three things to know before using it:

A cancelling callback stops the chain. Callbacks that would have run after it do not, which is what Foundry does when a handler vetoes. Do not use canCancel on a hook where other registrants must always see the event.
It works on any hook name, not only pre*. Whether false means anything is Foundry's decision -- hooks fired with Hooks.call honour it, hooks fired with Hooks.callAll do not.
canCancel inside options is not honoured, and logs a console warning saying so, because a registration that looks like it can veto and cannot is the worst failure available to this flag.

If you need cancellation on a hook where you would rather not depend on any of the above, registering a native Hooks.on and tracking your own teardown is a legitimate choice. Squire does this deliberately for the pre* family.

Other Methods

// Remove a specific callback
const removed = BlacksmithHookManager.removeCallback(callbackId);

// Cleanup by context
BlacksmithHookManager.disposeByContext('context-name');

// Get statistics and debugging info
BlacksmithHookManager.showHooks();
BlacksmithHookManager.showHookDetails();
BlacksmithHookManager.getStats();

Working Examples

Basic Hook Registration

const hookId = BlacksmithHookManager.registerHook({
    name: 'updateActor',
    description: 'My module: Track actor changes',
    context: 'my-module',
    priority: 3,
    callback: (actor, changes) => {
        console.log(`Actor ${actor.name} updated:`, changes);
    }
});

Hook with All Parameters

const fullHookId = BlacksmithHookManager.registerHook({
    name: 'updateActor',
    description: 'My module: Track actor changes',
    context: 'my-module',
    priority: 3,
    key: 'unique-actor-tracker', // Prevents duplicate registrations
    options: { 
        once: false,           // Don't auto-cleanup
        throttleMs: 100        // Max once per 100ms
    },
    callback: (actor, changes) => {
        console.log(`Actor ${actor.name} updated:`, changes);
    }
});

Combat Tracking Hook

const combatHookId = BlacksmithHookManager.registerHook({
    name: 'updateCombat',
    description: 'My module: Track combat changes',
    context: 'my-combat-tracker',
    priority: 2, // High priority - core functionality
    callback: (combat, changed) => {
        if (changed.round !== undefined) {
            console.log(`Round changed to ${changed.round}`);
        }
    }
});

UI Enhancement Hook

const uiHookId = BlacksmithHookManager.registerHook({
    name: 'renderChatMessageHTML',
    description: 'My module: Enhance chat messages',
    context: 'my-chat-enhancer',
    priority: 4, // Low priority - UI updates
    callback: (message, html, data) => {
        // `html` is a native HTMLElement on v13+, NOT jQuery. Use DOM methods.
        html.querySelector('.message-content')?.classList.add('my-enhanced-style');
    }
});

On v13+, html is a native HTMLElement, not jQuery. Two things to know:

The name: v13 core fires renderChatMessageHTML and passes a native HTMLElement. Registering renderChatMessage still works — HookManager silently rewrites it to renderChatMessageHTML and warns once — but register the real name.
The call: .addClass() is jQuery and throws TypeError. Blacksmith bolts a small .find() shim onto the element for backward compatibility, but that shim returns a plain Array with only .click attached — .find() survives, .addClass() does not. Use querySelector / classList instead.

One-time Hook with Auto-cleanup

const welcomeHookId = BlacksmithHookManager.registerHook({
    name: 'userConnected',
    description: 'My module: Welcome message',
    context: 'my-welcome',
    priority: 5,
    options: { once: true }, // Auto-cleanup after first execution
    callback: (user, connected) => {
        if (connected) console.log(`Welcome back, ${user.name}!`);
    }
});

Note: there is no userLogin hook in Foundry — the real hook is userConnected(user, connected), used above.

Performance-Optimized Hooks

// Throttle noisy hooks (e.g., updateToken)
const throttledHookId = BlacksmithHookManager.registerHook({
    name: 'updateToken',
    description: 'My module: Throttled token updates',
    context: 'my-token-tracker',
    priority: 4,
    options: { throttleMs: 50 }, // Max once per 50ms
    callback: (token, changes) => {
        console.log('Token updated:', token.name);
    }
});

// Debounce for final state — fire once after a burst of changes settles
const debouncedHookId = BlacksmithHookManager.registerHook({
    name: 'updateActor',
    description: 'My module: Debounced actor sync',
    context: 'my-actor-sync',
    priority: 4,
    options: { debounceMs: 300 }, // Wait 300ms after the last update
    callback: (actor, changes) => {
        console.log('Actor settled:', actor.name);
    }
});

Note: there is no searchInput hook in Foundry. Debounce is best shown on a hook that genuinely bursts, like updateActor (above) or updateToken. Remember debounceMs cannot be combined with once or throttleMs — see the options caveat above.

Priority Guidelines

Priority	Level	Use For
1	CRITICAL	System cleanup, critical features, must-run-first operations
2	HIGH	Core functionality, data validation, early processing
3	NORMAL	Most hooks, standard functionality (default)
4	LOW	Nice-to-have features, UI updates
5	LOWEST	Cosmetic features, debug hooks

// Priority 1 - System integrity
BlacksmithHookManager.registerHook({ name: 'canvasReady', priority: 1, ... });

// Priority 2 - Core features
BlacksmithHookManager.registerHook({ name: 'updateActor', priority: 2, ... });

// Priority 3 - Standard (default)
// NOTE: register 'renderChatMessageHTML' on v13+. Passing 'renderChatMessage' still works —
// HookManager silently rewrites it and warns — but see the caveat under UI Enhancement below.
BlacksmithHookManager.registerHook({ name: 'renderChatMessageHTML', priority: 3, ... });

// Priority 4 - UI enhancements
BlacksmithHookManager.registerHook({ name: 'renderApplication', priority: 4, ... });

// Priority 5 - Debug/cosmetic
BlacksmithHookManager.registerHook({ name: 'renderPlayers', priority: 5, ... });

Note: renderPlayerList is a v12 name. Foundry emits render{ClassName} for an Application and each of its parent classes; in v13 the player-list class is Players, so the hook is renderPlayers. renderPlayerList never fires on v13.

Performance Options

Throttling

Limit execution frequency for noisy hooks:

BlacksmithHookManager.registerHook({
    name: 'updateToken',
    options: { throttleMs: 50 }, // Max once per 50ms
    callback: (token, changes) => { /* ... */ }
});

Debouncing

Wait for activity to settle before running:

BlacksmithHookManager.registerHook({
    name: 'updateActor',
    options: { debounceMs: 300 }, // Fire once, 300ms after a burst of updates settles
    callback: (actor, changes) => { /* ... */ }
});

One-time Hooks

Auto-remove after first execution:

BlacksmithHookManager.registerHook({
    name: 'userConnected',
    options: { once: true },
    callback: (user, connected) => { /* ... */ }
});

Console Commands

Use these to debug and inspect hook registrations:

// Show hook summary (count, names)
BlacksmithAPIHooks()

// Detailed hook information by priority
BlacksmithAPIHookDetails()

// Raw hook statistics
BlacksmithAPIHookStats()

// Expanded details with full formatting
BlacksmithAPIHookExpandedDetails()

Command	Returns	Description
`BlacksmithAPIHooks()`	Object	Hook count, names, and summary data
`BlacksmithAPIHookDetails()`	Object	Hooks organized by priority levels
`BlacksmithAPIHookStats()`	Object	Statistical breakdown by priority/context
`BlacksmithAPIHookExpandedDetails()`	Console Output	Detailed hook information with full formatting

Best Practices

1. Use Direct Global Access

// GOOD: Use global objects directly
BlacksmithHookManager.registerHook(...)

// ALTERNATIVE: Store reference if preferred
const hookManager = BlacksmithHookManager;

2. Always Use Contexts

// GOOD: Descriptive context for cleanup
BlacksmithHookManager.registerHook({
    name: 'updateActor',
    context: 'my-module-actor-tracking',
    callback: () => { /* ... */ }
});

// BAD: No context makes cleanup difficult
BlacksmithHookManager.registerHook({
    name: 'updateActor',
    callback: () => { /* ... */ }
});

3. Provide Clear Descriptions

// GOOD: Clear, descriptive
BlacksmithHookManager.registerHook({
    name: 'updateActor',
    description: 'My Module: Track actor HP changes for health panel updates',
    callback: () => { /* ... */ }
});

// BAD: Vague
BlacksmithHookManager.registerHook({
    name: 'updateActor',
    description: 'Updates stuff',
    callback: () => { /* ... */ }
});

4. Use Appropriate Priorities

Use priority 3 (NORMAL) for most hooks
Only use 1 or 2 for critical/core functionality
Use 4 or 5 for cosmetic/debug features

5. Clean Up When Done

const myHookIds = [];

myHookIds.push(BlacksmithHookManager.registerHook({
    name: 'updateActor',
    context: 'my-module',
    callback: () => { /* ... */ }
}));

// Tie cleanup to something that actually fires — see the warning below.
// If you hold a context, one call removes every callback registered under it:
BlacksmithHookManager.disposeByContext('my-module');

Foundry has no module-unload event

Neither closeGame nor unloadModule is a Foundry hook — both appear zero times in Foundry v13, and nothing (Blacksmith included) ever calls Hooks.call('unloadModule'). Registering either succeeds silently and the callback never runs, so any cleanup written against them never executes.

Foundry does not unload modules at runtime: enabling or disabling a module forces a world reload, which tears down every hook, timer, and listener anyway. So there is no moment at which an "unregister my hooks" callback both fires and matters.

What to do:

Use context on every registerHook (see above). It costs nothing and makes bulk cleanup a single call if you ever have a real trigger — your own settings toggle, a window close, a feature being switched off at runtime.
Call disposeByContext() from your lifecycle, not from a hook you hope exists.
Do not add a closeGame / unloadModule listener and consider cleanup handled. It is not.

Debugging and Troubleshooting

Common Issues

Issue: "HookManager is not defined"

// Solution: Use global objects directly
BlacksmithHookManager.registerHook(...)

Issue: Hook not executing

// Check if hook is registered
const stats = BlacksmithHookManager.getStats();
console.log('Registered hooks:', stats.hooks);

// Verify hook name is correct (FoundryVTT hook names are case-sensitive)

Issue: Performance problems

// Use throttling for noisy hooks
BlacksmithHookManager.registerHook({
    name: 'updateToken',
    options: { throttleMs: 100 },
    callback: () => { /* ... */ }
});

// Use debouncing for user input
BlacksmithHookManager.registerHook({
    name: 'updateActor',
    options: { debounceMs: 500 },
    callback: () => { /* ... */ }
});

Error Handling Pattern

try {
    if (!BlacksmithHookManager) {
        throw new Error('HookManager not available');
    }
    
    const hookId = BlacksmithHookManager.registerHook({
        name: 'updateActor',
        description: 'My module: Actor update handler',
        context: 'my-module',
        priority: 3,
        callback: (actor, changes) => { /* ... */ }
    });
    
    console.log('Hook registered successfully:', hookId);
    
} catch (error) {
    console.error('Failed to register hook:', error);
    
    // Fallback to direct FoundryVTT hooks
    Hooks.on('updateActor', (actor, changes) => {
        // My logic here
    });
}

API Test Example

From the integration test suite in api-core.md:

const hookName = 'createActor';
const hookContext = 'my-module-id';

const hookResult = BlacksmithHookManager.registerHook({
    name: hookName,
    description: 'API Test Hook',
    context: hookContext,
    // Priority is 1-5. This example used to pass 50: it is accepted without complaint (there is no
    // validation), sorts dead last, and then vanishes from the debug tools — showHookDetails() only
    // iterates priorities 1..5, so a priority-50 hook is invisible to BlacksmithAPIHookExpandedDetails().
    priority: 3,
    key: `${hookContext}-${hookName}`,
    options: {},
    callback: async (actor) => {
        BlacksmithUtils.postConsoleAndNotification(
            'my-module-id', 
            'Hook triggered!', 
            { actorId: actor.id, name: actor.name }, 
            false, 
            false
        );
    }
});

console.log('Hook registration result:', hookResult);

api hookmanager

Blacksmith Hook Manager API

Overview

Access

Core API

Register a Hook

Parameter Order (Recommended)

What We Support

Cancellation (canCancel)

Other Methods

Working Examples

Basic Hook Registration

Hook with All Parameters

Combat Tracking Hook

UI Enhancement Hook

One-time Hook with Auto-cleanup

Performance-Optimized Hooks

Priority Guidelines

Performance Options

Throttling

Debouncing

One-time Hooks

Console Commands

Best Practices

1. Use Direct Global Access

2. Always Use Contexts

3. Provide Clear Descriptions

4. Use Appropriate Priorities

5. Clean Up When Done

Foundry has no module-unload event

Debugging and Troubleshooting

Common Issues

Error Handling Pattern

API Test Example

Related Documentation

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Cancellation (`canCancel`)