Understanding .stop() and .resume() Methods

Introduction

The .stop() and .resume() methods are powerful performance optimization tools in React Signify that allow you to control when UI updates happen. Think of them as a "pause" and "play" button for your component re-renders.

const sMySignify = signify(0);

sMySignify.stop();    // Pause UI updates
sMySignify.resume();  // Resume UI updates

How It Works: The Core Concept

The Key Insight

When you call .stop(), the state value still updates, but the UI doesn't re-render. When you call .resume(), the UI immediately updates to show the latest value.

const sCounter = signify(0);

// Normal behavior: value changes → UI updates
sCounter.set(1); // UI shows: 1
sCounter.set(2); // UI shows: 2

// With stop(): value changes → UI stays the same
sCounter.stop();
sCounter.set(3); // UI still shows: 2 (but sCounter.value is 3)
sCounter.set(4); // UI still shows: 2 (but sCounter.value is 4)

// With resume(): UI updates to latest value
sCounter.resume(); // UI now shows: 4

Why This Matters

This separation of state updates and UI updates gives you fine-grained control over performance:

• Prevent unnecessary re-renders during batch operations
• Reduce flickering during rapid state changes
• Improve performance with high-frequency updates
• Control animation timing more precisely

Step-by-Step Guide

Step 1: Basic Usage

const sCounter = signify(0);

// Normal updates
sCounter.set(1); // UI shows: 1
sCounter.set(2); // UI shows: 2

// Stop updates
sCounter.stop();
sCounter.set(3); // UI still shows: 2
sCounter.set(4); // UI still shows: 2

// Resume updates  
sCounter.resume(); // UI now shows: 4

Key Point: State changes, but UI only updates when not stopped.

Step 2: What Actually Happens

const sData = signify('hello');

sData.stop();
sData.set('world');
console.log(sData.value); // 'world' (state updated)
// But UI still shows 'hello'

sData.resume(); // UI now shows 'world'

Key Points:

• ✅ State always updates
• ❌ UI doesn't re-render when stopped
• ✅ UI catches up when resumed

When to Use Stop/Resume

✅ Good Use Cases

1. Batch Operations

const sCart = signify([]);

// Add multiple items at once
sCart.stop();
sCart.set(prev => { prev.value.push(item1, item2, item3); });
sCart.resume(); // Single re-render for all items

2. High-Frequency Updates

const sLiveData = signify(0);

// Throttle rapid updates
sLiveData.stop();
// ... many fast updates happen ...
setTimeout(() => sLiveData.resume(), 1000); // Update UI once per second

3. Animation Setup

const sPosition = signify({ x: 0, y: 0 });

// Prevent flicker during setup
sPosition.stop();
sPosition.set({ x: 100, y: 200 }); // Set initial position
sPosition.resume(); // Start animation

❌ Don't Use For

Simple Updates

// ❌ Overkill
sCounter.stop();
sCounter.set(5);
sCounter.resume();

// ✅ Just do this
sCounter.set(5);

User Input

// ❌ User can't see typing
input.stop();
input.set(value);
input.resume();

// ✅ Keep responsive
input.set(value);

Real-World Example

const sCart = signify([]);

// Add single item - normal update
const addOne = () => {
  sCart.set(prev => { prev.value.push(newItem); });
};

// Add multiple items - use stop/resume
const addMany = async () => {
  sCart.stop(); // Pause UI updates
  
  try {
    // Add many items (no re-renders during this)
    for (const item of manyItems) {
      sCart.set(prev => { prev.value.push(item); });
      await delay(100); // Simulate API call
    }
  } finally {
    sCart.resume(); // Single re-render with all items
  }
};

Result: Smooth experience instead of flickering UI during bulk operations.

Best Practices

✅ Always Use Try/Finally

// ✅ Safe - always resumes
mySignify.stop();
try {
  // ... operations
} finally {
  mySignify.resume();
}

// ❌ Unsafe - might not resume if error
mySignify.stop();
doSomething(); // If this fails...
mySignify.resume(); // ...this never runs!

✅ Keep Stops Short

// ✅ Quick batch
signify.stop();
update1();
update2();
signify.resume();

// ❌ Long stop = unresponsive UI
signify.stop();
setTimeout(() => signify.resume(), 5000); // Too long!

✅ Use for Performance Only

// ✅ Performance optimization
if (needsBatching) {
  signify.stop();
  batchUpdates();
  signify.resume();
}

// ❌ Don't use as app logic
signify.stop();
if (condition) signify.resume(); // UI might get stuck!

Summary

The .stop() and .resume() methods give you precise control over when UI updates happen:

Key Concepts

• State updates continue even when stopped
• UI updates pause until resumed
• Single re-render occurs when resumed with latest value

When to Use

• ✅ Batch operations (multiple state changes)
• ✅ High-frequency data updates
• ✅ Animation initialization
• ✅ Performance-critical scenarios

When NOT to Use

• ❌ Simple single updates
• ❌ User input handling
• ❌ Critical UI interactions
• ❌ Long-duration stops

Remember

• Always use try/finally to ensure resume
• Keep stop duration minimal
• Inform users when UI updates are paused
• Use for performance, not application logic

Master these methods and you'll have powerful tools for creating smooth, performant React applications!