swup VS view-transitions

https://swup.js.org/ single-page-app but with minimal framework, still along for the feel of an SPA

Sure, you can use any number of JS-avoidance libraries. I'm a fan of Turbo, and there's also htmx, Unpoly, Alpine, hyperscript, swup, barba.js, and probably others.

Swup is this nice page transition library I found recently : https://swup.js.org/

2. The newly released fragment-plugin [3] that provides a declarative API for dynamically replacing containers based on rules

I can now finally build websites that tick all three boxes:

1. Visually impressive, fun, and snappy by using swup's first-class support for animations[4], cache[5], and preload capacities[6], enhanced with fragment visits as seen on the demo site.

2. Accessible by being able to serve server-rendered semantic markup that will fully work even with JavaScript disabled (try it out on the demo site!). On top of that, swup's a11y plugin[7] will automatically announce page visits to assistive technologies and will focus the new `

` element after each visit.

3. Because now all I need for my fancy frontend is a bit of progressive JavaScript, I can choose whatever tool I like on the server, keeping complexity low and maintainability high. I can use SSGs like eleventy or Astro (the demo site is built using Astro!), I can use any CMS like WordPress or ProcessWire, or a framework like Laravel. And I don't have to maintain an additional node server for SSG!

And all it took was 20 years! ;)

[0] https://github.com/swup/swup

So what are View Transitions good for? In short, they allow adding animated page transitions. Although we already have several standard options to animate stuff on web pages (CSS Transitions, CSS Animations or the Web Animations API) and countless more options in particular JavaScript frameworks and libraries (Framer Motion for React, Vue Transitions, Svelte Transitions, Swup, Barba.js or Animate.css to name just a few), the web still lacks a generic, standards-based and easy-to-use solution to animate transitions between pages or during DOM updates. At least that’s what Google engineers say and I tend to agree with them.

Is https://turbo.hotwired.dev/ my replacement? Or Swup.js?

I've used https://swup.js.org/. Simple to setup with one of the built in/contributed themes, haven't tried building a custom theme however. Also has a lot of good plugins for eg. accessibility. I used it in combination with Astro so a static site with a separate html file for each page.

Like Gatsby or Next, Astro does not have any client side navigation. So each link click triggers a full page reload. Astro recommends to use Swup as mentioned here. Turbo is also another option though the team does not recommend it. I'm currently using Swup which I'll probably switch from or completely remove it as I have added TOC to MDX and clicking on a title is not redirecting the page to that particular section.

So let’s add the following CSS to the index template (Slim recognizes a css: block that just renders a normal tag):

/ app/views/counter/index.html.slim
/ (anywhere outside the Turbo Frame tag)
css:
  /* (1) */
  #counter {
    view-transition-name: counter;
    contain: layout;
  }

  /* (2) */
  @keyframes rotate-out {
    to {
      transform: rotate(90deg);
    }
  }

  @keyframes rotate-in {
    from {
      transform: rotate(-90deg);
    }
  }

  /* (3) */
  ::view-transition-old(counter) {
    animation-duration: 200ms;
    animation-name: -ua-view-transition-fade-out, rotate-out;
  }
  ::view-transition-new(counter) {
    animation-duration: 200ms;
    animation-name: -ua-view-transition-fade-in, rotate-in;
  }

Enter fullscreen mode Exit fullscreen mode

Let’s break this code down a bit:

1. The CSS selector #counter matches the counter div and the view-transition-name property names this area of the screen, for the purpose of View Transitions, as counter. This name will be used in the animation declarations below.

   The clone property currently must be added here for some reasons internal to the current View Transitions implementation in Chrome and must be set to paint or layout. This restriction is planned to be removed from the specification, though, and in fact I’ve heard that it is not needed in Chrome Canary any more.

2. The rotation animation keyframes are defined here. Note that while the transition also uses fade-in and fade-out animations, they don’t have to be defined here because the spec requires browsers to implement them natively under the name -ua-view-transition-fade-in/out.

3. The CSS animations for the counter (the View Transition area named counter) are configured here. The CSS selectors here are some of the pseudo-elements automatically created during the transition. The -old pseudo-element represents a screenshot of the old DOM state that should somehow disappear or ”go away“ from the viewport and the -new pseudo-element represents a live version of the final DOM state that should be brought into sight.

So, overall, this code selects a portion of the page and animates it independently from the rest of the page during Turbo Frames DOM updates. Behind the scenes, the default cross-fade for the rest of the page still also takes place, it just is not visible because all its elements are visually identical. The result looks like this:

A few initial tips & tricks

Does this work for Turbo Drive visits, too?

Sure it does and it’s actually pretty easy! All we have to do is define the same event handler as we did above but attach it to the turbo:before-render event instead. By default we’ll get a cross-fade animation of the whole page during Turbo Drive page visits.

Do not try to ”name“ the Turbo Frame itself

When playing with Turbo Frame View Transitions I first tried to use a custom animation for the whole Turbo Frame element by naming it via the view-transition-name property. For some reason, this does not work and you end up with a very cryptic and misleading error message in the console (yes I did have the contain property in the CSS declaration):

Aborting transition. Element must contain paint or layout for view-transition-name : counter

So, when using custom animations, an element from inside the Frame must be selected and named.

Debugging View Transitions

Since View Transitions are technically just normal CSS animations, they can be inspected with the Animations panel in the Dev Tools. Also, the automatically created pseudo-elements are visible in the Elements tab during the transitions:

Conclusions

I confess I am quite excited about the new View Transitions API. Among the things I particularly like about it are the following:

• It is surprisingly easy to plug this inside Hotwire Turbo and you get the default cross-fade transition animation immediately for free (in latest Chrome-like browsers, that is).
• Since this is implemented natively in the browser, the animations are highly optimized and performant.
• View Transitions should allow (today or in the future) building highly interactive transitions similar to those in Material Design.
• There is some initial support for Multi-Page Applications, too, which is great news because we can bring transition animations declared in CSS to our old but gold apps.
• It should be possible to use a different animation based on the ”direction“ of the visit (Back/Forward) using the Navigation API (also still experimental and not very well supported, though).

Things I am still concerned about:

• Browser support: the Firefox team evaluates it, the Safari team is silent. This will be a log run and making a polyfill is probably too difficult. For web sites where transition animations are critical, this is still a no go.

• If you’re not careful enough, the transition feels more fluid but also a little bit slower. The reason for it is that View Transitions start the animations at the moment when both the old and new DOM states are already rendered. This means that the exit animation is delayed until new content is available and until that time, nothing happens. Also, the entry animations for the new state usually delay its appearance a little bit more.

  This is not a problem of View Transitions themselves but rather a more generic one. If the exit animation (e.g. a fade out) started immediately after user interaction (e.g. a link click), sometimes the user would have to stare at a blank page until the new page content is grabbed, rendered and run through an entry animation. Still, some kind of support for this scenario (possibly with custom loaders or skeletons) would be nice.

• Tailwind support: I think the current Tailwind syntax does not allow targeting the HTML document-connected pseudo-elements so we have to resort to custom CSS (which is not a big problem, actually).

• All transitions target the whole page, there is currently no option to make, say, two components (Frames) animate totally independently. An initial proposal for ”scoped transitions“ can be found here.

Overall, I like this feature and wish it matures enough and gets wider support soon!

true, but HTML-only websites are often pretty clunky

infuriatingly, if HTML had just a bit more oomph, we could make a lot better websites with it, but they haven't been moving HTML forward as a hypermedia for decades now (see https://htmx.org for what I mean, they could implement this concept in the browser in a week, and it would change web development dramatically)

the upcoming view transitions API will help:

https://github.com/WICG/view-transitions

but, still, there are some really obvious and simple things that could be done to make HTML much more compelling (let's start by making PUT, PATCH and DELETE available in HTML!)

Cool answer: Look at shared element transition. this is gonna be really cool one day, sadly not yet out of the proposal state... https://github.com/WICG/shared-element-transitions

Native features faster: Quickest path to utilizing native features/UX improvements once they are released, no need to wait for a third party implementation. Example: shared element transitions first came to native, then were replicated on the web.

Lol yes, can’t edit now sorry.

1: https://github.com/WICG/shared-element-transitions

I took the experimental page transition API (a.k.a. shared element transitions) for a test drive with SvelteKit, and the result was pretty slick. You’ll need Chrome Canary with the chrome://flags/#document-transition flag enabled if you want to try this one out yourself — the original tweet has a video if you don’t want to jump through those hoops. There’s a live demo and a GitHub repo if you want to see how it was accomplished.

Here is link number 1 - Previous text "yet"

There's also the developer guide https://github.com/WICG/shared-element-transitions/blob/main/developer-guide.md.