Chapter 12: Project: Building an Interactive Image Gallery with Scoped Transitions

Welcome back, future web animation wizard! In our previous chapters, you’ve mastered the fundamentals of the View Transition API and started to dip your toes into the exciting world of Scoped View Transitions. You’ve learned how to make entire document navigations feel buttery smooth, and how to target specific areas for transition.

Now, it’s time to bring all that knowledge together and build something truly cool and interactive! In this chapter, we’re going to construct a dynamic image gallery. When you click on a thumbnail, the main image will gracefully transition to the new selection, and when you select an image, it will appear to expand from the thumbnail itself. This isn’t just about making things look pretty; it’s about creating a delightful user experience that feels intuitive and modern. Get ready to flex those coding muscles and see the magic of Scoped View Transitions in action!

Before we dive in, make sure you’re comfortable with basic HTML, CSS, and JavaScript, especially DOM manipulation and event handling. A solid grasp of the core document.startViewTransition() API from earlier chapters will also be super helpful, as we’ll be extending those concepts to specific elements using element.startViewTransition().

What are Scoped View Transitions (A Quick Recap)?

Remember how the regular View Transition API (document.startViewTransition()) handles transitions for the entire document? It’s fantastic for full-page navigations, but sometimes you only want a specific part of your page to animate, without affecting everything else. That’s where Scoped View Transitions come in!

Think of it like this: if document.startViewTransition() is like repainting an entire room, element.startViewTransition() is like repainting just one wall, or even just a picture frame on that wall. It allows you to initiate a view transition on a specific DOM subtree, giving you much finer control. This means:

1. Localized Transitions: Only elements within the specified subtree (and their ::view-transition pseudo-elements) participate in the transition.
2. Concurrent Transitions (Future Potential): While the spec is still evolving, the ultimate goal is to enable multiple independent scoped transitions to run simultaneously on different parts of the page. This is a huge step forward for complex interactive UIs!
3. The Key Method: Instead of document.startViewTransition(), we’ll be using element.startViewTransition() on a specific HTML element.

As of late 2025, Scoped View Transitions (often referred to as Element-scoped View Transitions) are actively being developed and tested, primarily in Chromium-based browsers, often behind experimental flags. The element.startViewTransition() method is the proposed API for this, as detailed in the WICG shared-element-transitions repository (https://github.com/WICG/shared-element-transitions/blob/main/scoped-transitions.md). We’ll be using this modern approach!

Project Structure and Design

For our interactive image gallery, we’ll need a simple setup:

• A Main Display Area: This is where the currently selected image will be shown in a larger format.
• A Thumbnail Grid: A collection of smaller images that, when clicked, will change the main display.

We’ll use a single HTML file (index.html), a CSS file (style.css), and a JavaScript file (script.js).

Here’s the basic visual idea:

+---------------------------------+
|          Main Image Area        |
|  (Displays the selected image)  |
+---------------------------------+
|                                 |
|  +-----+  +-----+  +-----+      |
|  | Th1 |  | Th2 |  | Th3 |  ... |
|  +-----+  +-----+  +-----+      |
|                                 |
+---------------------------------+

When you click Th2, the image in the Main Image Area will transition smoothly from where Th2 was, or at least morph into the new image.

Step-by-Step Implementation: Building Our Gallery

Let’s get our hands dirty and start coding!

Step 1: Setting Up the Basic HTML Structure

First, we need the skeleton of our gallery. Create an index.html file and add the following:

<!-- index.html -->
<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Scoped View Transitions Gallery</title>
    <link rel="stylesheet" href="style.css">
</head>
<body>
    <div class="gallery-container">
        <h1>My Awesome Scoped Image Gallery</h1>

        <div class="main-image-display">
            <!-- This will hold the large, selected image -->
            <img id="mainImage" src="https://via.placeholder.com/600x400/007bff/ffffff?text=Select+an+Image" alt="Selected Image">
        </div>

        <div class="thumbnail-grid">
            <!-- Thumbnails will go here -->
            <img class="thumbnail" src="https://via.placeholder.com/150x100/FF5733/ffffff?text=Image+1" alt="Thumbnail 1" data-full-src="https://via.placeholder.com/600x400/FF5733/ffffff?text=Full+Image+1">
            <img class="thumbnail" src="https://via.placeholder.com/150x100/33FF57/ffffff?text=Image+2" alt="Thumbnail 2" data-full-src="https://via.placeholder.com/600x400/33FF57/ffffff?text=Full+Image+2">
            <img class="thumbnail" src="https://via.placeholder.com/150x100/5733FF/ffffff?text=Image+3" alt="Thumbnail 3" data-full-src="https://via.placeholder.com/600x400/5733FF/ffffff?text=Full+Image+3">
            <img class="thumbnail" src="https://via.placeholder.com/150x100/FF33A1/ffffff?text=Image+4" alt="Thumbnail 4" data-full-src="https://via.placeholder.com/600x400/FF33A1/ffffff?text=Full+Image+4">
            <img class="thumbnail" src="https://via.placeholder.com/150x100/33A1FF/ffffff?text=Image+5" alt="Thumbnail 5" data-full-src="https://via.placeholder.com/600x400/33A1FF/ffffff?text=Full+Image+5">
        </div>
    </div>

    <script src="script.js"></script>
</body>
</html>

Explanation:

• We have a gallery-container to hold everything.
• main-image-display wraps the img element (#mainImage) that will show the large version of the selected image.
• thumbnail-grid contains several img elements, each with the class thumbnail.
• Crucially, each thumbnail also has a data-full-src attribute. This is a custom HTML attribute that stores the URL of the larger image corresponding to that thumbnail. We’ll use this in our JavaScript!

Step 2: Adding Basic CSS Styling

Now, let’s make our gallery look presentable. Create a style.css file and add these styles:

/* style.css */
body {
    font-family: 'Segoe UI', Tahoma, Geneva, Verdana, sans-serif;
    display: flex;
    justify-content: center;
    align-items: flex-start; /* Align to top */
    min-height: 100vh;
    margin: 0;
    background-color: #f0f2f5;
    color: #333;
    padding: 20px;
    box-sizing: border-box;
}

.gallery-container {
    background-color: #fff;
    border-radius: 12px;
    box-shadow: 0 8px 24px rgba(0, 0, 0, 0.1);
    padding: 30px;
    max-width: 900px;
    width: 100%;
    text-align: center;
}

h1 {
    color: #007bff;
    margin-bottom: 30px;
    font-size: 2.2em;
}

.main-image-display {
    width: 100%;
    height: 400px; /* Fixed height for consistency */
    background-color: #e0e0e0;
    border-radius: 8px;
    overflow: hidden; /* Ensures image doesn't spill */
    margin-bottom: 30px;
    display: flex;
    justify-content: center;
    align-items: center;
}

.main-image-display img {
    max-width: 100%;
    max-height: 100%;
    object-fit: contain; /* Ensures the image fits within the box without cropping */
    display: block; /* Remove extra space below image */
    border-radius: 8px;
}

.thumbnail-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(120px, 1fr));
    gap: 15px;
    justify-content: center;
}

.thumbnail {
    width: 100%;
    height: 100px; /* Fixed height for thumbnails */
    object-fit: cover; /* Crop to fill thumbnail area */
    border-radius: 6px;
    cursor: pointer;
    transition: transform 0.2s ease, box-shadow 0.2s ease;
    border: 3px solid transparent; /* For selected state */
}

.thumbnail:hover {
    transform: translateY(-3px);
    box-shadow: 0 6px 16px rgba(0, 0, 0, 0.15);
}

/* Style for selected thumbnail (will be added via JS) */
.thumbnail.selected {
    border-color: #007bff;
    box-shadow: 0 0 0 4px rgba(0, 123, 255, 0.4);
}

Explanation:

• Basic layout with flexbox to center the gallery.
• gallery-container provides a nice card-like appearance.
• main-image-display is given a fixed height and object-fit: contain for its image to ensure the full image is visible, even if it has different aspect ratios.
• thumbnail-grid uses CSS Grid for a responsive layout of thumbnails.
• thumbnail images are styled to be clickable and have a hover effect.
• A .selected class is defined for thumbnails, which we’ll add with JavaScript to highlight the currently active thumbnail.

At this point, open index.html in your browser. You should see a static gallery layout with placeholder images. No interactivity yet!

Step 3: Initial JavaScript - Making Thumbnails Interactive

Now, let’s add the basic JavaScript to swap the main image when a thumbnail is clicked. Create a script.js file:

// script.js
document.addEventListener('DOMContentLoaded', () => {
    const mainImage = document.getElementById('mainImage');
    const thumbnails = document.querySelectorAll('.thumbnail');
    const mainImageDisplay = document.querySelector('.main-image-display'); // We'll need this for scoped transitions

    let currentSelectedThumbnail = null; // To keep track of the currently selected thumbnail

    // Function to update the main image
    function updateMainImage(newSrc, clickedThumbnail) {
        mainImage.src = newSrc;
        mainImage.alt = clickedThumbnail.alt.replace('Thumbnail', 'Full Image');

        // Update selected class for thumbnails
        if (currentSelectedThumbnail) {
            currentSelectedThumbnail.classList.remove('selected');
        }
        if (clickedThumbnail) {
            clickedThumbnail.classList.add('selected');
            currentSelectedThumbnail = clickedThumbnail;
        }
    }

    // Add click listeners to all thumbnails
    thumbnails.forEach(thumbnail => {
        thumbnail.addEventListener('click', (event) => {
            const fullSrc = event.target.dataset.fullSrc;
            updateMainImage(fullSrc, event.target);
        });
    });

    // Initialize the gallery with the first thumbnail selected
    if (thumbnails.length > 0) {
        updateMainImage(thumbnails[0].dataset.fullSrc, thumbnails[0]);
    }
});

Explanation:

• We wait for the DOM to be fully loaded using DOMContentLoaded.
• We get references to our mainImage and all thumbnail elements.
• updateMainImage is a helper function that takes a new image source and the clicked thumbnail element. It updates the src and alt of the mainImage and manages the selected class on thumbnails.
• We loop through each thumbnail and attach a click event listener.
• When a thumbnail is clicked, we retrieve its data-full-src and pass it to updateMainImage.
• Finally, we initialize the gallery by selecting the first thumbnail programmatically.

Test this in your browser. When you click a thumbnail, the main image should change instantly. Notice how abrupt the change is? This is exactly what View Transitions are designed to fix!

Step 4: Introducing element.startViewTransition() for a Scoped Transition

Now for the exciting part! We’ll wrap our image update logic in an element.startViewTransition() call.

Crucial Note on Browser Support (2025-12-05): Scoped View Transitions (using element.startViewTransition()) are still an experimental feature. To enable them in Chromium-based browsers (like Chrome, Edge, Brave), you might need to go to chrome://flags (or edge://flags, etc.) and enable “Experimental Web Platform features”. Search for “View Transitions” or “Scoped View Transitions”. Without this, element.startViewTransition() might not be available or might behave like a regular DOM update.

Let’s modify our script.js:

// script.js (updated)
document.addEventListener('DOMContentLoaded', () => {
    const mainImage = document.getElementById('mainImage');
    const thumbnails = document.querySelectorAll('.thumbnail');
    const mainImageDisplay = document.querySelector('.main-image-display'); // This is our scope!

    let currentSelectedThumbnail = null;

    // Function to update the main image
    function updateMainImage(newSrc, clickedThumbnail) {
        // Check if Scoped View Transitions are supported on the element
        if (!mainImageDisplay.startViewTransition) {
            // Fallback for browsers that don't support element.startViewTransition()
            console.warn("Scoped View Transitions not supported on this element. Falling back to instant update.");
            mainImage.src = newSrc;
            mainImage.alt = clickedThumbnail.alt.replace('Thumbnail', 'Full Image');
            if (currentSelectedThumbnail) {
                currentSelectedThumbnail.classList.remove('selected');
            }
            if (clickedThumbnail) {
                clickedThumbnail.classList.add('selected');
                currentSelectedThumbnail = clickedThumbnail;
            }
            return;
        }

        // We want the transition to happen ONLY within the mainImageDisplay element
        // So we call startViewTransition on that element.
        mainImageDisplay.startViewTransition(() => {
            // The DOM changes inside this callback will be captured by the transition
            mainImage.src = newSrc;
            mainImage.alt = clickedThumbnail.alt.replace('Thumbnail', 'Full Image');

            // Update selected class for thumbnails
            if (currentSelectedThumbnail) {
                currentSelectedThumbnail.classList.remove('selected');
            }
            if (clickedThumbnail) {
                clickedThumbnail.classList.add('selected');
                currentSelectedThumbnail = clickedThumbnail;
            }
        });
    }

    // Add click listeners to all thumbnails
    thumbnails.forEach(thumbnail => {
        thumbnail.addEventListener('click', (event) => {
            const fullSrc = event.target.dataset.fullSrc;
            updateMainImage(fullSrc, event.target);
        });
    });

    // Initialize the gallery with the first thumbnail selected
    if (thumbnails.length > 0) {
        updateMainImage(thumbnails[0].dataset.fullSrc, thumbnails[0]);
    }
});

Explanation of Changes:

1. We added a mainImageDisplay constant, which is the DOM element we want to scope our transition to.
2. Feature Detection: We added if (!mainImageDisplay.startViewTransition) to check if the browser supports this experimental API. It’s always good practice to provide a fallback.
3. mainImageDisplay.startViewTransition(() => { ... });: This is the core change! Now, all DOM updates (changing mainImage.src, updating alt, and managing selected classes) are wrapped inside this callback. The browser will take a “snapshot” of mainImageDisplay before these changes, apply the changes, and then take another “snapshot” after. It then animates between these two states.

Try it out! Reload index.html. You should now see a subtle cross-fade animation when you click thumbnails. It’s much smoother than before, right? This is the default browser transition.

Step 5: Enhancing with view-transition-name for a “Shared Element” Effect

The cross-fade is nice, but what if we want the image to appear as if it’s expanding from the thumbnail? This is where view-transition-name becomes incredibly powerful, even within a scoped transition. We’ll use it to tell the browser: “Hey, these two elements (the clicked thumbnail and the main image) are conceptually the same thing, just in different states.”

To achieve this, we need to dynamically assign view-transition-name to the currently selected thumbnail and the main image.

Modify your script.js again:

// script.js (further updated)
document.addEventListener('DOMContentLoaded', () => {
    const mainImage = document.getElementById('mainImage');
    const thumbnails = document.querySelectorAll('.thumbnail');
    const mainImageDisplay = document.querySelector('.main-image-display');

    let currentSelectedThumbnail = null;

    // Function to update the main image
    function updateMainImage(newSrc, clickedThumbnail) {
        if (!mainImageDisplay.startViewTransition) {
            console.warn("Scoped View Transitions not supported on this element. Falling back to instant update.");
            mainImage.src = newSrc;
            mainImage.alt = clickedThumbnail.alt.replace('Thumbnail', 'Full Image');
            if (currentSelectedThumbnail) {
                currentSelectedThumbnail.classList.remove('selected');
            }
            if (clickedThumbnail) {
                clickedThumbnail.classList.add('selected');
                currentSelectedThumbnail = clickedThumbnail;
            }
            return;
        }

        mainImageDisplay.startViewTransition(() => {
            // 1. Remove view-transition-name from the previously selected thumbnail (if any)
            //    This ensures only the *active* thumbnail participates in the transition.
            if (currentSelectedThumbnail) {
                currentSelectedThumbnail.style.viewTransitionName = '';
            }

            // 2. Assign a unique view-transition-name to the clicked thumbnail
            //    This tells the browser: "This element is special for this transition."
            //    We'll use a generic name like 'gallery-thumbnail' for simplicity.
            //    It's important that the 'new' state element (mainImage) also has this name.
            clickedThumbnail.style.viewTransitionName = 'gallery-thumbnail';

            // 3. Update the main image content
            mainImage.src = newSrc;
            mainImage.alt = clickedThumbnail.alt.replace('Thumbnail', 'Full Image');

            // 4. Assign the SAME view-transition-name to the main image
            //    This is crucial! It links the thumbnail and the main image.
            mainImage.style.viewTransitionName = 'gallery-thumbnail';

            // 5. Update selected class for thumbnails
            if (currentSelectedThumbnail) {
                currentSelectedThumbnail.classList.remove('selected');
            }
            if (clickedThumbnail) {
                clickedThumbnail.classList.add('selected');
                currentSelectedThumbnail = clickedThumbnail;
            }
        });
    }

    // Add click listeners to all thumbnails
    thumbnails.forEach(thumbnail => {
        thumbnail.addEventListener('click', (event) => {
            const fullSrc = event.target.dataset.fullSrc;
            updateMainImage(fullSrc, event.target);
        });
    });

    // Initialize the gallery with the first thumbnail selected
    if (thumbnails.length > 0) {
        // Make sure to set the view-transition-name for the initial state as well
        thumbnails[0].style.viewTransitionName = 'gallery-thumbnail';
        mainImage.style.viewTransitionName = 'gallery-thumbnail';
        updateMainImage(thumbnails[0].dataset.fullSrc, thumbnails[0]);
    }
});

Explanation of Changes:

• clickedThumbnail.style.viewTransitionName = 'gallery-thumbnail';: Before the DOM update, we dynamically assign a view-transition-name to the thumbnail that was just clicked. This marks it as a “shared element.”
• mainImage.style.viewTransitionName = 'gallery-thumbnail';: After updating the mainImage’s src, we assign the same view-transition-name to the mainImage. This tells the browser: “The element named gallery-thumbnail in the ‘old’ state (the thumbnail) should transition into the element also named gallery-thumbnail in the ’new’ state (the main image).”
• if (currentSelectedThumbnail) { currentSelectedThumbnail.style.viewTransitionName = ''; }: It’s vital to remove the view-transition-name from the previously selected thumbnail. If you don’t, multiple elements might end up with the same view-transition-name at the same time, which can lead to unexpected (and often broken) transition behavior. A view-transition-name should generally be unique within the scope of a transition.
• Initialization: We also ensure the first thumbnail and main image get the view-transition-name when the page loads, so the initial click also benefits from the transition.

Now, refresh your browser and click a thumbnail. You should see a much more interesting transition! The new image appears to grow and move from the position of the clicked thumbnail to the main image display area. This is the power of shared element transitions within a scoped context!

Step 6: Customizing the Transition with CSS

The default shared element transition is pretty good, but we can make it even better with custom CSS animations. We’ll target the ::view-transition pseudo-elements that the browser creates.

Add the following CSS to your style.css file:

/* style.css (updated with transition styles) */

/* ... (previous CSS) ... */

/* Custom animations for the 'gallery-thumbnail' shared element */
::view-transition-group(gallery-thumbnail) {
    animation-duration: 0.5s; /* Make the transition a bit slower */
    animation-timing-function: ease-in-out; /* Smoother acceleration/deceleration */
}

::view-transition-old(gallery-thumbnail) {
    /* Style for the 'old' image (the thumbnail) */
    animation: fade-out 0.5s ease-in-out forwards;
    object-fit: cover; /* Keep object-fit consistent */
}

::view-transition-new(gallery-thumbnail) {
    /* Style for the 'new' image (the main image) */
    animation: fade-in 0.5s ease-in-out forwards;
    object-fit: contain; /* Keep object-fit consistent */
}

/* Keyframes for our custom fade */
@keyframes fade-out {
    from { opacity: 1; }
    to { opacity: 0; }
}

@keyframes fade-in {
    from { opacity: 0; }
    to { opacity: 1; }
}

/* For the global transition container, if any global elements were involved
   (less relevant for purely scoped transitions, but good to know) */
::view-transition {
    /* You can apply general transition properties here if needed */
}

/* You can also target the entire image pair if you want */
::view-transition-image-pair(gallery-thumbnail) {
    /* For example, add a subtle shadow to the transitioning element */
    box-shadow: 0 10px 30px rgba(0, 0, 0, 0.2);
    border-radius: 8px; /* Match the main image display */
}

Explanation of CSS Additions:

• ::view-transition-group(gallery-thumbnail): This targets the container that holds both the “old” and “new” snapshots of our gallery-thumbnail element. We’re setting a longer animation-duration and a smoother animation-timing-function for the overall movement.
• ::view-transition-old(gallery-thumbnail): This targets the snapshot of the element before the DOM change (the clicked thumbnail). We apply a fade-out animation to it.
• ::view-transition-new(gallery-thumbnail): This targets the snapshot of the element after the DOM change (the main image). We apply a fade-in animation.
• @keyframes fade-out and @keyframes fade-in: These are standard CSS keyframe animations to create the fading effect. forwards ensures the animation stays at its end state.
• ::view-transition-image-pair(gallery-thumbnail): This pseudo-element represents the combination of the old and new images, allowing you to style them as a single entity during the transition. Here, we’ve added a box-shadow and border-radius to make the transitioning image look more polished.

Now, save both files and refresh your browser. Click on the thumbnails. You should observe a more pronounced and customized transition, with the image smoothly fading and moving!

Mini-Challenge: Deselecting the Main Image

You’ve done a fantastic job creating the gallery! Now, for a small challenge to solidify your understanding.

Challenge: Add functionality so that if a user clicks the currently displayed main image, it deselects, and the mainImage reverts to its initial placeholder state (e.g., “Select an Image”), and the selected class is removed from all thumbnails. This should also happen with a smooth view transition!

Hint:

• You’ll need another event listener, this time on the mainImage itself.
• Inside that listener, you’ll want to call mainImageDisplay.startViewTransition() again.
• Within the transition callback, reset mainImage.src to the placeholder, clear its view-transition-name, and remove the selected class from currentSelectedThumbnail. Also, clear currentSelectedThumbnail.
• You might want to ensure the placeholder image also has view-transition-name: gallery-thumbnail during the transition if you want it to participate in the shared element animation as it disappears. Or, you could let it fade out as a “non-shared” element. Experiment!

What to observe/learn:

• How to initiate a transition when an element is “removed” or “changed back” to a default state.
• The importance of clearing view-transition-name when an element is no longer conceptually “shared.”

    // Add click listener to the main image for deselection
    mainImage.addEventListener('click', () => {
        if (!mainImageDisplay.startViewTransition) {
            console.warn("Scoped View Transitions not supported on this element. Falling back to instant update.");
            mainImage.src = "https://via.placeholder.com/600x400/007bff/ffffff?text=Select+an+Image";
            mainImage.alt = "Selected Image";
            if (currentSelectedThumbnail) {
                currentSelectedThumbnail.classList.remove('selected');
                currentSelectedThumbnail.style.viewTransitionName = ''; // Clear name
            }
            currentSelectedThumbnail = null;
            mainImage.style.viewTransitionName = ''; // Clear name
            return;
        }

        mainImageDisplay.startViewTransition(() => {
            // Reset the main image to its placeholder state
            mainImage.src = "https://via.placeholder.com/600x400/007bff/ffffff?text=Select+an+Image";
            mainImage.alt = "Selected Image";

            // Remove view-transition-name from the main image
            // This tells the browser it's no longer a "shared element"
            mainImage.style.viewTransitionName = '';

            // Remove selected class and view-transition-name from the previously selected thumbnail
            if (currentSelectedThumbnail) {
                currentSelectedThumbnail.classList.remove('selected');
                currentSelectedThumbnail.style.viewTransitionName = ''; // Crucial to clear it!
            }
            currentSelectedThumbnail = null; // No thumbnail is selected now
        });
    });

Common Pitfalls & Troubleshooting

1. element.startViewTransition is not a function:

   • Cause: The browser you’re using doesn’t support Scoped View Transitions (or element.startViewTransition()). As of 2025-12-05, this is still an experimental API.
   • Solution: Ensure you’re using a Chromium-based browser (like Chrome Canary, Edge Dev) and have enabled “Experimental Web Platform features” in chrome://flags (or edge://flags). Our code includes a fallback, but for development, you’ll want it enabled.

2. No Transition (Instant Change) Even with startViewTransition:

   • Cause 1: The DOM changes inside the startViewTransition callback are not actually modifying the visible content of the scoped element.
   • Solution: Double-check that mainImage.src or other relevant properties are indeed changing within the callback.
   • Cause 2: The view-transition-name is not correctly applied or is not unique.
   • Solution: Use the browser’s DevTools (Elements tab). Look for the ::view-transition pseudo-elements. If they aren’t appearing, or if your view-transition-name isn’t showing up as expected, there’s likely an issue with its assignment. Remember to clear view-transition-name from elements when they are no longer “active” in a transition.

3. Janky or Unexpected Animations:

   • Cause 1: Multiple elements have the same view-transition-name simultaneously. view-transition-name should generally be unique per transition.
   • Solution: Ensure your JavaScript logic correctly adds and removes view-transition-name only from the active elements.
   • Cause 2: Overly complex CSS animations or large images.
   • Solution: Simplify your CSS keyframes initially. Ensure images are optimized for web use. For debugging, temporarily disable custom CSS animations to see if the default transition is smooth.

4. Accessibility Concerns:

   • Cause: View transitions can be disorienting for some users, especially those with motion sensitivities.
   • Solution: Always provide a way for users to disable animations if possible. Consider using the prefers-reduced-motion media query in your CSS to offer a less intense transition or no transition at all:

   @media (prefers-reduced-motion) {
       ::view-transition-group(gallery-thumbnail),
       ::view-transition-old(gallery-thumbnail),
       ::view-transition-new(gallery-thumbnail) {
           animation: none !important; /* Disable animations */
       }
       /* You might also want to prevent the JS from calling startViewTransition */
       /* You'd need to add a check in your JS: */
       /* if (window.matchMedia('(prefers-reduced-motion)').matches) {
           // Skip transition, just update DOM
       } else {
           // Run transition
       } */
   }
   

Summary

Phew! You’ve just built a sleek, interactive image gallery powered by the cutting-edge Scoped View Transitions API. Let’s recap what you’ve learned and achieved:

• Scoped Transitions with element.startViewTransition(): You now understand how to initiate view transitions on specific DOM subtrees, giving you granular control over animations within your page.
• Shared Element Transitions: By dynamically applying the same view-transition-name to a thumbnail and the main image, you created a compelling “shared element” effect where the image appears to transition from one location to another.
• Customizing with CSS Pseudo-elements: You learned how to target and style the ::view-transition-group(), ::view-transition-old(), ::view-transition-new(), and ::view-transition-image-pair() pseudo-elements to create bespoke animation effects.
• Dynamic view-transition-name Management: You implemented JavaScript logic to add and remove view-transition-name attributes, which is crucial for correct and predictable transition behavior, especially when elements enter and exit the “shared” state.
• Practical Application: You’ve built a real-world project, demonstrating how to integrate these advanced animation techniques into an interactive user interface.

This chapter has pushed your understanding of View Transitions to a new level, showcasing their power in creating truly immersive and delightful web experiences. The ability to scope transitions opens up a world of possibilities for complex components and micro-interactions.

In the next chapter, we’ll continue to explore more advanced techniques, perhaps diving into more intricate custom animations or looking at how to combine different types of transitions. Keep experimenting, keep building, and keep being awesome!