Inspecting Animations in DevTools

I stumbled upon the Animation panel in Chrome’s DevTools the other day and almost jumped out of my seat with pure joy. Not only was I completely unaware that such a thing exists, but it was better than what I could’ve hoped: it lets you control and manipulate CSS animations and visualize how everything works under the hood.

To access the panel, head to More Tools → Animations in the top right-hand menu when DevTools is open:

Many of the tutorials I found about this were pretty complicated, so let’s take a step back and look at a smaller example to begin with: here’s a demo where the background-color of the html element will transition from black to orange on hover:

html { cursor: pointer; background-color: #333; transition: background-color 4s ease;
} html:hover { background-color: #e38810;
}

Let’s imagine that we want to nudge that transition time down from 4s. It can get pretty annoying just bumping that number up and down in the element inspector. I typically would’ve opened up DevTools, found the element in the DOM and then ever-so-slowly manipulate it by typing in a value or using the keyboard directional keys. Instead, we can fire up that demo, open DevTools, and switch to the Animation tab which ought to look something like this:

By default, Chrome will be “listening” for animations to take place. Once they do, they’ll be added to the list. See how those animation blocks are displayed sort of like an audio wave? That’s one frame, or act, of an animation and you can see on the timeline above it each frame that follows it. On an animation itself, the inspector will even show us which property is being changed, like background-color or transform. How neat is that?

We can then modify that animation by grabbing that bar and moving it about:

…and it updates the animation right away — no more clicking and editing an animation the old way! Also, you might’ve noticed that hovering over an animation frame will highlight the element that’s being animated in blue. This is handy if you’re editing a complex animation and forget what that crazy weird pseudo element does. If you have multiple animations on a page, then you can see them all listed in that section just like in this demo:

What we’re doing here is animating both the .square and the .circle when hovering on the html element, so there’s effectively two separate divs being animated in the same time frame — that’s why you can see them in the same section just like that.

I can see that inspecting animations in this way could be super useful for tiny icon design, too. Take this pen of Hamburger menu animations by Jesse Couch where you might want to slow everything down to get things just right. Well, with the animation inspector tool you can do exactly that:

Those buttons in the top left-hand corner will control the playback speed of the animation. So hitting 10% will slow things to a crawl — giving you enough time to really futz with things until they’re perfect.

I’ve focused on Chrome here but it’s not the only browser with an animation inspector — Firefox’s tool is in every way just as useful. The only immediate difference I found was that Chrome will listen for any animations on a page and will display them once their captured. But, with Firefox, you have to inspect the element and only then will it show you the animations attached to that element. So, if you’re doing super complex animations, then Chrome’s tool might be a smidge more helpful.

Animation Inspector Documentation

  • Walkthrough on Google Developers
  • Animation inspector in Firefox – MDN

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Finger-friendly numerical inputs with `inputmode`

Forms are often a nightmare on mobile. We can make the process as pain-free as possible by reacting to context. Input fields that expect numerical values should have a numerical most) larger screens, number inputs come with an incrementer/decrementer button. It’s a useful piece of UI we get for free by default. It does, however, make this kind of input totally inappropriate for a credit card number, for example.

A default number input that displays the up and down arrows that allow users to increase and decrease numbers in the field.
The default UI for number inputs looks something like this in all desktop browsers

The spec itself makes this clear.

The type=number state is not appropriate for input that happens to only consist of numbers but isn’t strictly speaking a number. For example, it would be inappropriate for credit card numbers or US postal codes. A simple way of determining whether to use type=number is to consider whether it would make sense for the input control to have a spinbox interface (e.g., with “up” and “down” arrows). Getting a credit card number wrong by 1 in the last digit isn’t a minor mistake, it’s as wrong as getting every digit incorrect. So it would not make sense for the user to select a credit card number using “up” and “down” buttons. When a spinbox interface is not appropriate, type=text is probably the right choice (possibly with a pattern attribute).

It’s easy to hide the up and down buttons with CSS:

input[type="number"] { -moz-appearance: textfield;
}
input[type="number"]::-webkit-inner-spin-button, input[type="number"]::-webkit-outer-spin-button { -webkit-appearance: none; margin: 0; }

It’s important to note that this isn’t the only difference between a number and text input. You should definitely follow the spec on this point! Some older browsers will strip out leading zeros for number inputs which would be a big problem for US ZIP codes. The often-useful maxlength attribute is ignored on number inputs.

Why would anybody dislike such a useful input?

The answer comes down to validation and using the input for the wrong thing. The number input performs input sanitization by default. If a user enters anything that isn’t a valid number, the value will be equal to an empty string — regardless of what the user can see on the screen.

This input sanitization can trip developers up, and there’s no way to turn it off. If you want to allow input that isn’t a valid number, don’t use type="number".

A screenshot showing a number input that is filled with numbers and includes dashes between some of the numbers.
Number input in Chrome. This might be valid input for your use case, but it’s illegitimate in the eyes of the number input.
var numberinput = document.querySelector('input[type="number"]')
numberinput.value // will be ""

This might not be what you would intuitively expect. However, if you follow the spec and only use the number input for what its designed for — actual numbers — this behavior is unproblematic.

Number Input Alternatives

iOS Solution: Use the `pattern` Attribute on a Text Input

On iOS devices, using the pattern attribute with a value of [0-9]* will bring up the numeric keypad. This only works with this exact pattern — you can’t allow any extra characters.

<label for="creditcard">credit card number:</label> <input pattern="[0-9]*" type="text" name="creditcard">
The iOS number keyboard that displays only numbers one through ten and no other special characters.
iOS with pattern attribute

Bear in mind that an iPhone won’t let the user switch keyboard type when this keyboard is displayed. Make sure these are the only keys they need to fill in the input correctly.

If you want to bring up a keypad of large numeric keys on iOS, you need to use the pattern attribute even on number inputs. Otherwise, you’ll get small and finger-friendly buttons:

A screenshot of the iOS keyboard displaying both numbers and letters.
iOS keypad for <input type="number">

A Better Solution: `inputmode`

inputmode has been a WHATWG spec for a couple of years, and has finally been implemented by Chrome as of version 66:

This browser support data is from Caniuse, which has more detail. A number indicates that browser supports the feature at that version and up.

Desktop

Chrome Opera Firefox IE Edge Safari
66 No 20 No No No

Mobile / Tablet

iOS Safari Opera Mobile Opera Mini Android Android Chrome Android Firefox
No No No No No No

For the widest support possible, it can be combined with the pattern attribute for iOS:

<label for="creditcard">credit card number:</label> <input inputmode="numeric" pattern="[0-9]*" type="text" name="creditcard">

This gives developers full control of the mobile UI without any extra baggage. It makes the UI finger-friendly while being more versatile than the pattern attribute as we can allow any characters we like. It controls one thing — and one thing only. inputmode is a great solution for those cases when it’s inappropriate to use type="number".

Some people would go further and ditch type="number" altogether once inputmode has better support. I’m not convinced that’s wise, but type="number" can be problematic.

if (numberInput.validity.valueMissing) {
errorMessage.textContent = "field must not be empty"
}
A screenshot of a number input filled with numbers and special characters with an error message below it that informs the user the field is empty.
Contrary to the human eye, the field is empty…

If you want to explicitly warn of empty number inputs, you’ll need to use:

if (numberInput.validity.valueMissing && !numberInput.validity.badInput) {
errorMessage.textContent = "field must not be empty"
}

According to Google, users abandon purchases twice as often on mobile as compared to desktop. Sales on phones account for only one third of all completed online purchases. Clearly people don’t tolerate fumbling through badly designed forms and jabbing at tiny inputs. Data entry needs to be effortless. While browser support is currently low, we’re only really waiting on mobile browsers. Desktop support is largely irrelevant. The input elements introduced by HTML5 are great, but they miss some edge cases. This can fill in some gaps.

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Radial Gradient Recipes

Radial gradients are pretty dang cool. It’s amazing we can paint the background of an element with them so easily. Easily is a relative term though. It’s certainly easier than needing to create a graphic in third-party software to use as the background, and the syntax is highly learnable. But it’s also not that easy to remember if you don’t use it often, and it’s more complicated than linear-gradient().

I figured I’d put together a page of reference examples, so if you know what you need but forget the syntax, it’s easy to find that starter code example here.

Centered Bursts

The simplest possible syntax places the first color in the center of the element and the second color on the outside and that’s that:

See the Pen Radial Gradient – Centered by Chris Coyier (@chriscoyier) on CodePen.

That will stretch the gradient into an ellipse on a non-square element though. If you don’t like that, you can force the shape into a circle, like the second example here demonstrates:

See the Pen Radial Gradient – Circle vs. Ellipse by Chris Coyier (@chriscoyier) on CodePen.

You can also control the size by literally saying how large the circle/ellipse should be (the final color will still stretch to cover the element) by:

  • Using a keyword closest-side, farthest-side, closest-corner, farthest-corner
  • Explicitly saying like radial-gradient(circle 100px, ...)
  • Using color stops like radial-gradient(#56ab2f, #a8e063 150px)

See the Pen Radial Gradient – Sizing by Chris Coyier (@chriscoyier) on CodePen.

Here’s some of that stuff in use:

See the Pen Usage of Radial Gradients by Chris Coyier (@chriscoyier) on CodePen.

See the Pen Lit text by Chris Coyier (@chriscoyier) on CodePen.

Positioned

Besides controlling the size and shape of the gradient, the other big trick to know with radial gradients is that you can position the center of them.

This is one of the shortcomings, I find, with gradient generators. They help you pick colors and color stops and stuff, but they usually punt on the positioning stuff.

This is a beautiful gradient tool, but doesn’t help with positioning or sizing. Some of them do help a little with positioning (see “Expert” settings), but don’t expose all the possibilities.

The center of a radial gradient doesn’t have to be in the center! For example, you can position the center in the top left like this:

.element { background: radial-gradient( at top left, var(--light), var(--dark) /* using variables just for fun! */ )
}

Here’s all the four corners:

See the Pen Positioned Radial Gradients by Chris Coyier (@chriscoyier) on CodePen.

You can also be very specifically positioned. Here’s an example of a gradient positioned exactly 195px from the left along the bottom of the element. It also has a specific size, but otherwise does the default ellipse shape:

.element { background: radial-gradient( 150px 40px at 195px bottom, #666, #222 );
}

See the Pen Specifically positioned gradient by Chris Coyier (@chriscoyier) on CodePen.

Another little thing to know is that you can use transparent in the gradients to expose the color behind if that’s needed, or partially transparent colors like rgba(255, 255, 255, 0.5) to do the same at a colorized color stop.

Also, radial gradients can be used with multiple backgrounds, applying multiple of them to a single element, even overlapping!

.element { background: radial-gradient( circle at top left, rgba(255, 255, 255, 0.5), transparent 100px ), radial-gradient( circle at top right, rgba(255, 255, 255, 0.5), transparent 100px ), radial-gradient( at bottom left, rgba(255, 0, 255, 0.5), transparent 400px ), radial-gradient( at bottom right, rgba(255, 100, 100, 0.5), transparent 400px );
}

See the Pen Multiple Gradients by Chris Coyier (@chriscoyier) on CodePen.

To highlight the idea that the center of the gradient can be anywhere, here’s a gradient that follows the mouse:

See the Pen Radial Gradient Move With Mouse by Leo Sammarco (@lsammarco) on CodePen.

Resources

People tend to think about browser support, and rightfully so, but don’t think too hard about it in this case. We’re at pretty much across the board support even without any prefixes.

  • There is also repeating-linear-gradient() and here Ana Tudor gets into some detail and use cases.
  • Need some colors that go nicely togehter in a gradient? uiGradients is nice.
  • MDN on radial-gradient
  • See our complete guide to all gradients here!

OK bye!

See the Pen CSS Sunset Sunrise by Marty Saetre (@msaetre) on CodePen.

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Understanding React `setState`

React components can, and often do, have state. State can be anything, but think of things like whether a user is logged in or not and displaying the correct username based on which account is active. Or an array of blog posts. Or if a modal is open or not and which tab within it is active.

React components with state render reconciliation. The reconciliation process is the way React updates the DOM, by making changes to the component based on the change in state. When the request to setState() is triggered, React creates a new tree containing the reactive elements in the component (along with the updated state). This tree is used to figure out how the Search component’s setState Pen by Kingsley Silas Chijioke (@kinsomicrote) on CodePen.

Let’s register the component and define the markup for the Understanding React `setState` appeared first on CSS-Tricks.

Server-Side Visualization With Nightmare

This is an extract from chapter 11 of Ashley Davis’s book Data Wrangling with JavaScript now available on the Manning Early Access Program. I absolutely love this idea as there is so much data visualization stuff on the web that relies on fully functioning client side JavaScript and potentially more API calls. It’s not nearly as robust, accessible, or syndicatable as it could be. If you bring that data visualization back to the server, you can bring progressive enhancement to the party. All example code and data can be found on GitHub.

When doing exploratory coding or data analysis in Node.js it is very useful to be able to render a visualization from our data. If we were working in browser-based JavaScript we could choose any one of the many charting, graphics, and visualization libraries. Unfortunately, under Node.js, we don’t have any viable options, so how otherwise can we achieve this?

We could try something like faking the DOM under Node.js, but I found a better way. We can make our browser-based visualization libraries work for us under Node.js using a headless browser. This is a browser that has no user interface. You can think of it as a browser that is invisible.

I use Nightmare under Node.js to capture visualizations to PNG and PDF files and it works really well!

The headless browser

When we think of a web-browser we usually think of the graphical software that we interact with on a day to day basis when browsing the web. Normally we interact with such a browser directly, viewing it with our eyes and controlling it with our mouse and keyboard as shown in Figure 1.

Figure 1: The normal state of affairs: our visualization renders in a browser and the user interacts directly with the browser

A headless browser on the other hand is a web-browser that has no graphical user interface and no direct means for us to control it. You might ask what is the use of a browser that we can’t directly see or interact with.

Well, as developers we would typically use a headless browser for automating and testing web sites. Let’s say that you have created a web page and you want to run a suite of automated tests against it to prove that it works as expected. The test suite is automated, which means it is controlled from code and this means that we need to drive the browser from code.

We use a headless browser for automated testing because we don’t need to directly see or interact with the web page that is being tested. Viewing such an automated test in progress is unnecessary, all we need to know is if the test passed or failed — and if it failed we would like to know why. Indeed, having a GUI for the browser under test would actually be a hindrance for a continuous-integration or continuous-deployment server, where many such tests can run in parallel.

So headless browsers are often used for automated testing of our web pages, but they are also incredibly useful for capturing browser-based visualizations and outputting them to PNG images or PDF files. To make this work we need a web server and a visualization, we must then write code to instance a headless browser and point it at our web server. Our code then instructs the headless browser to take a screenshot of the web page and save it to our file system as a PNG or PDF file.

Figure 2: We can use a headless browser under Node.js to capture our visualization to a static image file

Nightmare is my headless browser of choice. It is a Node.js library (installed via npm) that is built on Electron. Electron is a framework normally used for building cross-platform desktop apps that are based on web-technologies.

Why Nightmare?

It’s called Nightmare, but it’s definitely not a Nightmare to use. In fact, it’s the simplest and most convenient headless browser that I’ve used. It automatically includes Electron, so to get started we simply install Nightmare into our Node.js project as follows:

npm install --save nightmare

That’s all we need to install Nightmare and we can start using it immediately from JavaScript!

Nightmare comes with almost everything we need: A scripting library with an embedded headless browser. It also includes the communication mechanism to control the headless browser from Node.js. For the most part it’s seamless and well-integrated to Node.js.

Electron is built on Node.js and Chromium and maintained by GitHub and is the basis for a number of popular desktop applications.

Here are the reasons that I choose to use Nightmare over any other headless browser:

  • Electron is very stable.
  • Electron has good performance.
  • The API is simple and easy to learn.
  • There is no complicated configuration (just start using it).
  • It is very well integrated with Node.js.

Nightmare and Electron

When you install Nightmare via npm it automatically comes with an embedded version of Electron. So, we can say that Nightmare is not just a library for controlling a headless browser, it effectively is the headless browser. This is another reason I like Nightmare. With some of the other headless browsers, the control library is separate, or it’s worse than that and they don’t have a Node.js control library at all. In the worst case, you have to roll your own communication mechanism to control the headless browser.

Nightmare creates an instance of the Electron process using the Node.js child_process module. It then uses inter-process communication and a custom protocol to control the Electron instance. The relationship is shown in Figure 3.

Figure 3: Nightmare allows us to control Electron running as a headless browser

Our process: Capturing visualizations with Nightmare

So what is the process of capturing a visualization to an image file? This is what we are aiming at:

  1. Acquire data.
  2. Start a local web server to host our visualization
  3. Inject our data into the web server
  4. Instance a headless browser and point it at our local web server
  5. Wait for the visualization to be displayed
  6. Capture a screenshot of the visualization to an image file
  7. Shutdown the headless browser
  8. Shutdown the local web server

Prepare a visualization to render

The first thing we need is to have a visualization. Figure 4 shows the chart we’ll work with. This a chart of New York City yearly average temperature for the past 200 years.

Figure 4: Average yearly temperature in New York City for the past 200 years

To run this code you need Node.js installed. For this first example we’ll also use live-server (any web server will do) to test the visualization (because we haven’t created our Node.js web server yet), install live server as follows:

npm install -g live-server

Then you can clone the example code repo for this blog post:

git clone https://github.com/Data-Wrangling-with-JavaScript/nodejs-visualization-example

Now go into the repo, install dependencies and run the example using live-server

cd nodejs-visualization-example/basic-visualization
bower install
live-server

When you run live-server your browser should automatically open and you should see the chart from Figure 4.

It’s a good idea to check that your visualization works directly in a browser before you try and capture it in a headless browser; there could easily be something wrong with it and problems are much easier to troubleshoot in a real browser than in the headless browser. live-server has live reload built-in, so now you have a nice little setup here when you can edit and improve the chart interactively before you try to capture it under Node.js.

This simple line chart was constructed with C3. Please take a look over the example code and maybe look at some of the examples in the C3 gallery to learn more about C3.

Starting the web server

To host our visualization, we need a web server. It’s not quite enough that we have a web server, we also need to be able to dynamically start and stop it. Listing 1 shows the code for our web server.

Listing 1 – Code for a simple web server that can be started and stopped

const express = require('express');
const path = require('path'); module.exports = { start: () => { // Export a start function so we can start the web server on demand. return new Promise((resolve, reject) => { const app = express(); const staticFilesPath = path.join(__dirname, "public"); // Make our 'public' sub-directory accessible via HTTP. const staticFilesMiddleWare = express.static(staticFilesPath); app.use('/', staticFilesMiddleWare); const server = app.listen(3000, err => { // Start the web server! if (err) { reject(err); // Error occurred while starting web server. } else { resolve(server); // Web server started ok. } }); }); }
}

The code module in listing 1 exports a start function that we can call to kickstart our web server. This technique, being able to start and stop our web server, is also very useful for doing automated integration testing on a web site. Imagine that you want to start your web server, run some tests against it and then stop it at the end.

So now we have our browser-based visualization and we have a web server that can be started and stopped on demand. These are the raw ingredients we need for capturing server-side visualizations. Let’s mix it up with Nightmare!

Rendering the web page to an image

Now let’s flesh out the code to capture a screenshot of the visualization with Nightmare. Listing 2 shows the code that instances Nightmare, points it at our web server and then takes the screenshot.

Listing 2 – Capturing our chart to an image file using Nightmare

const webServer = require('./web-server.js');
const Nightmare = require('nightmare'); webServer.start() // Start the web server.
.then(server => { const outputImagePath = "./output/nyc-temperatures.png"; const nightmare = new Nightmare(); // Create the Nightmare instance. return nightmare.goto("http://localhost:3000") // Point the browser at the web server we just started. .wait("svg") // Wait until the chart appears on screen. .screenshot(outputImagePath) // Capture a screenshot to an image file. .end() // End the Nightmare session. Any queued operations are completed and the headless browser is terminated. .then(() => server.close()); // Stop the web server when we are done.
})
.then(() => { console.log("All done :)");
})
.catch(err => { console.error("Something went wrong :("); console.error(err);
});

Note the use of the goto function, this is what actually directs the browser to load our visualization.

Web pages usually take some time to load. That’s probably not going to be very long, especially as we are running a local web server, but still we face the danger of taking a screenshot of the headless browser before or during its initial paint. That’s why we must call the wait function to wait until the chart’s <svg> element appears in the browser’s DOM before we call the screenshot function.

Eventually, the end function is called. Up until now we have effectively built a list of commands to send to the headless browser. The end function actually sends the commands to the browser, which takes the screenshot and outputs the file nyc-temperatures.png. After the image file has been captured we finish up by shutting down the web server.

You can find the completed code under the capture-visualization sub-directory in the repo. Go into the sub-directory and install dependencies:

cd nodejs-visualization-example/capture-visualization
cd public bower install
cd ..
npm install
live-server

Now you can try the code for yourself:

node index.js

This has been an extract from chapter 11 of Data Wrangling with JavaScript now available on the Manning Early Access Program. Please use this discount code fccdavis3 for a 37% discount. Please check The Data Wrangler for new updates on the book.

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Native-Like Animations for Page Transitions on the Web

Some of the most inspiring examples I’ve seen of front-end development have involved some sort of page transitions that look slick like they do in mobile apps. However, even though the imagination for these types of interactions seem to abound, their presence on actual sites that I visit do not. There are a number of ways to accomplish these types of movement!

Here’s what we’ll be building:

Demo Site

GitHub Repo

We’ll build out the simplest possible distillation of these concepts so that you can apply them to any application, and then I’ll also provide the code for this more complex app if you’d like to dive in.

Today we’ll be discussing how to create them with Vue and Nuxt. There are a lot of moving parts in page transitions and animations (lol I kill me), but don’t worry! Anything we don’t have time to cover in the article, we’ll link off to with other resources.

Why?

The web has come under critique in recent years for appearing “dated” in comparison to native iOS and Android app experiences. Transitioning between two states can reduce cognitive load for your user, as when someone is scanning a page, they have to create a mental map of everything that’s contained on it. When we move from page to page, the user has to remap that entire space. If an element is repeated on several pages but altered slightly, it mimics the experience we’ve been biologically trained to expect — no one just pops into a room or changes suddenly; they transition from another room into this one. Your eyes see someone that’s smaller relative to you. As they get closer in proximity to you, they get bigger. Without these transitions, changes can be startling. They force the user to remap placement and even their understanding of the same element. It is for this reason that these effects become critical in an experience that helps the user feel at home and gather information quickly on the web.

The good news is, implementing these kind of transitions is completely doable. Let’s dig in!

Prerequisite Knowledge

If you’re unfamiliar with Nuxt and how to work with it to create Vue.js applications, there’s another article I wrote on the subject here. If you’re familiar with React and Next.js, Nuxt.js is the Vue equivalent. It offers server-side rendering, code splitting, and most importantly, hooks for page transitions. Even though the page transition hooks it offers are excellent, that’s not how we’re going to accomplish the bulk of our animations in this tutorial.

In order to understand how the transitions we’re working with today do work, you’ll also need to have basic knowledge around the <transition /> component and the difference between CSS animations and transitions. I’ve covered both in more detail here. You’ll also need basic knowledge of the <transition-group /> component and this Snipcart post is a great resource to learn more about it.

Even though you’ll understand everything in more detail if you read these articles, I’ll give you the basic gist of what’s going on as we encounter things throughout the post.

Getting Started

First, we want to kick off our project by using the Vue CLI to create a new Nuxt project:

# if you haven’t installed vue cli before, do this first, globally:
npm install -g @vue/cli
# or
yarn global add @vue/cli # then
vue init nuxt/starter my-transitions-project
npm i
# or
yarn # and
npm i vuex node-sass sass-loader
# or
yarn add vuex node-sass sass-loader

Great! Now the first thing you’ll notice is that we have a pages directory. Nuxt will take any .vue files in that directory and automatically set up routing for us. Pretty awesome. We can make some pages to work with here, in our case: about.vue, and users.vue.

Setting Up Our Hooks

As mentioned earlier, Nuxt offers some page hooks which are really nice for page to page transitions. In other words, we have hooks for a page entering and leaving. So if we wanted to create an animation that would allow us to have a nice fade from page to page, we could do it because the class hooks are already available to us. We can even name new transitions per page and use JavaScript hooks for more advanced effects.

But what if we have some elements that we don’t want to leave and re-enter, but rather transition positions? In mobile applications, things don’t always leave when they move from state to state. Sometimes they transition seamlessly from one point to another and it makes the whole application feel very fluid.

Step One: Vuex Store

The first thing we’ll have to do is set up a centralized state management store with Vuex because we’re going to need to hold what page we’re currrently on.

Nuxt will assume this file will be in the store directory and called index.js:

import Vuex from 'vuex' const createStore = () => { return new Vuex.Store({ state: { page: 'index' }, mutations: { updatePage(state, pageName) { state.page = pageName } } })
} export default createStore

We’re storing both the page and we create a mutation that allows us to update the page.

Step Two: Middleware

Then, in our middleware, we’ll need a script that I’ve called pages.js. This will give us access to the route that’s changing and being updated before any of the other components, so it will be very efficient.

export default function(context) { // go tell the store to update the page context.store.commit('updatePage', context.route.name)
}

We’ll also need to register the middleware in our nuxt.config.js file:

module.exports = { ... router: { middleware: 'pages' }, ...
}

Step Three: Register Our Navigation

Now, we’ll go into our layouts/default.vue file. This directory allows you to set different layouts for different page structures. In our case, we’re not going to make a new layout, but alter the one that we’re reusing for every page. Our template will look like this at first:

<template> <div> <nuxt/> </div>
</template>

And that nuxt/ tag will insert anything that’s in the templates in our different pages. But rather than reusing a nav component on every page, we can add it in here and it will be presented consistently on every page:

<template> <div> <app-navigation /> <nuxt/> </div>
</template>
<script>
import AppNavigation from '~/components/AppNavigation.vue' export default { components: { AppNavigation }
}
</script>

This is also great for us because it won’t rerender every time the page is re-routed. It will be consistent on every page and, because of this, we cannot plug into our page transition hooks but instead we can build our own with what we built between Vuex and the Middleware.

Step Four: Create our Transitions in the Navigation Component

Now we can build out the navigation, but I’m also going to use this SVG here to do a small demo of basic functionality we’re going to implement for a larger application

<template> <nav> <h2>Simple Transition Group For Layout: {{ page }}</h2> <!--simple navigation, we use nuxt-link for routing links--> <ul> <nuxt-link exact to="/"><li>index</li></nuxt-link> <nuxt-link to="/about"><li>about</li></nuxt-link> <nuxt-link to="/users"><li>users</li></nuxt-link> </ul> <br> <!--we use the page to update the class with a conditional--> <svg :class="{ 'active' : (page === 'about') }" xmlns="http://www.w3.org/2000/svg" width="200" height="200" viewBox="0 0 447 442"> <!-- we use the transition group component, we need a g tag because it’s SVG--> <transition-group name="list" tag="g"> <rect class="items rect" ref="rect" key="rect" width="171" height="171"/> <circle class="items circ" key="circ" id="profile" cx="382" cy="203" r="65"/> <g class="items text" id="text" key="text"> <rect x="56" y="225" width="226" height="16"/> <rect x="56" y="252" width="226" height="16"/> <rect x="56" y="280" width="226" height="16"/> </g> <rect class="items footer" key="footer" id="footer" y="423" width="155" height="19" rx="9.5" ry="9.5"/> </transition-group> </svg> </nav>
</template>
<script>
import { mapState } from 'vuex' export default { computed: mapState(['page'])
}
</script>

We’re doing a few things here. In the script, we bring in the page name from the store as a computed value. mapState will let us bring in anything else from the store, which will handy later when we deal with a lot of user information.

In the template, we have a regular nav with nuxt-links, which is what we use for routing links in Nuxt. We also have class that will be updated on a conditional based on the page (it will change to .active when it’s the about page.

We’re also using the <transition-group> component around a number of elements that will change positions. The <transition-group> component is a bit magical because it applies the concepts of FLIP under the hood. If you’ve heard of FLIP before, you’re going to be super excited to hear this because it’s a really performant way of animating on the web but usually takes a lot of calculations to implement. If you haven’t heard of FLIP before, it’s definitely good to read up to understand how it works, and maybe more importantly, all of the stuff you no longer have to do to make this kind of effect work! Can I get a “Hell yeah!”

Here is the CSS that makes this work. We basically state how we’d like all of the elements to be positioned on that “active” hook that we made. Then we tell the elements to have a transition applied if something changes. You’ll notice I’m using 3D transforms even if I’m just moving something along one X or Y axis because transforms are better for performance than top/left/margin for reducing paint and I want to enable hardware acceleration.

.items,
.list-move { transition: all 0.4s ease;
} .active { fill: #e63946; .rect { transform: translate3d(0, 30px, 0); } .circ { transform: translate3d(30px, 0, 0) scale(0.5); } .text { transform: rotate(90deg) scaleX(0.08) translate3d(-300px, -35px, 0); } .footer { transform: translateX(100px, 0, 0); }
}

Here is a reduced codepen without the page transitions, but just to show the movement:

See the Pen layout transition-group by Sarah Drasner (@sdras) on CodePen.

I want to point out that any implementations I use here are choices that I’ve made for placement and movement- you can really create any effect you like! I am choosing SVG here because it communicates the concept of layout in a small amount of code, but you don’t need to use SVG. I’m also using transitions instead of animation because of how declarative they are by nature- you are in essence stating: “I want this to be repositioned here when this class is toggled in Vue”, and then the transition’s only job is to describe the movement as anything changes. This is great for this use-case because it’s very flexible. I can then decide to change it to any other conditional placement and it will still work.

Great! This will now give us the effect, smooth as butter between pages, and we can still give the content of the page a nice little transition as well:

.page-enter-active { transition: opacity 0.25s ease-out;
} .page-leave-active { transition: opacity 0.25s ease-in;
} .page-enter,
.page-leave-active { opacity: 0;
}

I’ve also added in one of the examples from the Nuxt site to show that you can still do internal animations within the page as well:

View GitHub Repo

Ok, that works for a small demo, but now let’s apply it to something more real-world, like our example from before. Again, the demo site is here and the repo with all of the code is here.

It’s the same concept:

  • We store the name of the page in the Vuex store.
  • Middleware commits a mutation to let the store know the page has changed.
  • We apply a special class per page, and nest transitions for each page.
  • The navigation stays consistent on each page but we have different positions and apply some transitions.
  • The content of the page has a subtle transition and we build in some interactions based on user events

The only difference is that this is a slightly more involved implementation. The CSS that’s applied to the elements will stay the same in the navigation component. We can tell the browser what position we want all the elements to be in, and since there’s a transition applied to the element itself, that transition will be applied and it will move to the new position every time the page has changed.

// animations
.place { .follow { transform: translate3d(-215px, -80px, 0); } .profile-photo { transform: translate3d(-20px, -100px, 0) scale(0.75); } .profile-name { transform: translate3d(140px, -125px, 0) scale(0.75); color: white; } .side-icon { transform: translate3d(0, -40px, 0); background: rgba(255, 255, 255, 0.9); } .calendar { opacity: 1; }
}

That’s it! We keep it nice and simple and use flexbox, grid and absolute positioning in a relative container to make sure everything translates easily across all devices and we have very few media queries through this project. I’m mainly using CSS for the nav changes because I can declaratively state the placement of the elements and their transitions. For the micro-interactions of any user-driven event, I’m using JavaScript and GreenSock, because it allows me to coordinate a lot of movement very seamlessly and stabilizes transform-origin across browsers, but there are so many ways you could implement this. There are a million ways I could improve this demo application, or build on these animations, it’s a quick project to show some possibilities in a real-life context.

Remember to hardware accelerate and use transforms, and you can achieve some beautiful, native-like effects. I’m excited to see what you make! The web has so much potential for beautiful movement, placement, and interaction that reduces cognitive load for the user.

The post Native-Like Animations for Page Transitions on the Web appeared first on CSS-Tricks.

Choosing a Responsive Email Framework: MJML vs. Foundation for Emails

Implementing responsive email design can be a bit of a drag. Building responsive emails isn’t simple at all, it is like taking a time machine back to 2001 when we were all coding website layouts in tables using Dreamweaver and Fireworks.

But there’s hope! We have tools available that can make building email much easier and more like coding a modern site. Let’s take a look at a couple of different frameworks that set out to simplify things for us.

First, the Situation

You have to be compatible with lots of old email clients, many of which don’t even support the most basic web standards (floats, anyone?). You also have to deal with all sorts of webmail clients which, for security or technical reasons, have made their own opinionated choices about how to display your precious email.

Furthermore, now emails are read from different devices, with very different viewports and requirements.

The best solution, as is often the case, would be to keep things simple and stick to basic one-column designs, using multiple columns only for menus or simple interface elements of known width. You can produce great, effective designs using only one column, after all.

However end-users and clients, who are used to the “normal” browser-based web, may hold their email-viewing experience to the same high standards they do for viewing web pages in terms of graphics and responsiveness. Therefore, complex designs are expected: multiple columns, different behaviors on mobile devices as opposed to desktops, lots of images, etc., all of which have to be implemented consistently and pixel-perfect across all email clients. What options are available to make all that happen?

Option 1: Build From Scratch

One option you could choose is coding each email by hand, keeping it simple, and testing it while you go. This is a viable option only if:

  1. You have a very simple design to implement.
  2. You have direct control of the design, so you can eventually simplify things if you can’t come out with a consistent solution for what you intended to do.
  3. You can accept some degree of degradation on some older clients: you don’t mind if your email won’t look exactly the same (or even plain bad) in old Outlook clients, for example.
  4. You have a lot of time on your hands.

Obviously, you need to test your design heavily. Campaign Monitor has a great CSS guide you can reference during the build process and is sort of like Can I Use, but for email. After that, I recommend using automated test suites like Litmus or Email on Acid. Both offer you a complete testing suite and previews of how your email will look like on a huge variety of email clients. Expect some surprises, though, because often the same design does not look correct even on the same email client, if viewed on different browsers, or different operating systems. Fonts will render differently, margins will change, and so on.

Screenshot of the same email design tested on different devices on Email on Acid.

Option 2: Use a Boilerplate Template

Another option is to use one of the various boilerplates available, like Sean Powelll’s, which you can find here. Boilerplates already address many of the quirks of different email clients and platforms. This is sensible if:

  1. You are working alone, or on a small team.
  2. You have lots of experience, so you already know most of the quirks of email formatting because you’ve met them before.
  3. You have set up your own tools for managing components (for different newsletters which share some pieces of design), inlining styles (and yes, you should keep inlining your styles if your emails target an international audience), and have some kind of development toolkit in place (be it Gulp, Grunt or something similar) which will automate all of that for you.
  4. You have the kind of approach where you’d like to control everything in the code you produce and don’t like to rely on external tools.
  5. You prefer to solve your own bugs instead of having to solve possible bugs caused by the tool you are using.

Option 3: Use a Framework

However, if any of the following points are valid for you:

  1. You have to produce a lot of email templates with shared components.
  2. The job has to be carried out by a team of developers, who might change and/or have a variable degree of proficiency and experience with email implementation.
  3. You have little or no control on the original design.

…then you will likely benefit a lot from using a framework.

Currently, two of the most interesting and popular frameworks available are MJML and Foundation for Emails. The biggest advantages in using either framework is that they have already solved for you most of the quirks of email clients. They also provide you with an established workflow you can follow, both alone and as a team. They also handle responsive design very well, albeit differently from one another.

Let’s look at an overview of both frameworks and compare the best use cases for each before drawing some conclusions.

MJML

MJML is a project that was created internally by Mailjet, a company specializing in email marketing tools. It was then open-sourced. It works with its own custom, HTML-like templating language, using its own tags. For example:

<mj-text>Your text here</mj-text>

When you compile the final code, MJML will convert their tags into HTML for everything from tables to custom components they have created for you, all using its internal engine. It takes out the heavy lifting for creating complex markup and it’s all been tested.

MJML has a set of standard components. They include sections, columns, groups, buttons, images, social links (which are very easy to create), tables, accordions, etc. They even include a pre-styled carousel, which should work in most clients. All of these components translate well into responsive emails, apart from the “invoice” component which I could not get to work in my tests. All of these components have parameters you can pass in your code to customize their appearance.

For example, the social links component allows you to stack icons vertically and horizontally, and to choose background colors for the related icons. There are actually a lot more parameters you can play with, all with the intent of allowing for greater flexibility. Even the logo image files are already included in the package, which is a great plus.

Here’s a preview of a simple configuration of the social links component:

Screenshot from the MJML website.

You can also create your own custom components, or use components created by the community. There is just one community component available at the moment, however.

MJML handles responsiveness automatically, meaning that components will switch from multi-column (more items in the same row) to single-column (items are put one under the other instead of side-by-side) without any active intervention from the developer. This is a very flexible solution, and works fine in most cases, but it gives the developer a little less control over what happens exactly in the template. As the docs mention, it’s worth keeping mind that:

For aesthetics purposes, MJML currently supports a maximum of 4 columns per section.

This is most likely not only an aesthetic preference but also about limiting possible drawbacks of having too many columns. The more columns you have, the more unpredictable the output, I guess.

How to Work With MJML

MJML can work as a command line tool, which you can install with npm, and output your files locally, with commands like:

$ mjml -r index.mjml -o index.html

This can be integrated in your build procedure via Gulp or the like, and in your development work by using a watch command, which will update your preview every time you save:

$ mjml --watch index.mjml -o index.html

MJML has plugins for Atom and Sublime Text. In Atom, it even supplies a real-time preview of your layout, which can be regenerated on every save. I haven’t tried it personally, but it seems very interesting:

Image from Atom.io

MJML also has its own simple desktop app, and it’s free. You can set up your code and components, have it build your designs for you, and get a real-time preview of the results, both for mobile and for desktop. I find that it works pretty well on Ubuntu, but the only drawback I’ve found is that you should never, never, never open your files with another editor while they’re open on the app, because the app crashes and the content of the file gets lost.

Here are some screenshots of the previews at work:

Desktop preview of email
Mobile preview of email

The app can also be integrated with a free Mailjet account, which allows you to send test emails immediately to yourself. This is very handy to quickly check problematic clients if you have them available directly. (I would suggest taking out that old Windows machine you have in the storage room to check things in Outlook, and to do it as often as possible.) However, I would still recommend using either Litmus or Email on Acid to test your emails cross-client before deploying them because you can never be too careful and email standards can change just like they do in browsers.

Overall, I have found MJML very easy to use. However, when I tried to make a pixel-perfect template which was identical to the design our client requested, I had some difficulties dealing with custom margins for some images. Not all of the component parameters available worked as expected from their description in the documentation. In particular, I had some problems customizing image margins and padding between desktop and mobile.

Advantages

  • Pre-built components
  • Integration with Mailjet
  • Easy to use, with instant preview of your work (on Atom and Desktop App)

Disadvantages

  • A bit less reliable than Foundation for Emails if you have to do pixel-perfect designs
  • Some components have parameters that don’t work as expected
  • Desktop App not perfectly stable
  • Does not come with a structured set of folders for your content (see Foundation below)

Foundation for Emails

Foundation for Emails (formerly known as Ink — insert obligatory Prince quote here) is a framework by Zurb, the same folks who brought us the responsive front-end framework, Foundation for Sites.

When you download the Starter Kit you get a full development environment, complete with Node.js commands to run your project. It will setup a Node routine and even open your browser to give you an immediate preview of your work.

The files you have to use are already organized in folders and subfolders, with a clear indication of where to put your stuff. For example, it has directories specifically for partials, templates and images. I find this feature very important, because it is very easy to end up using different folders when you work on a team, and this leads to a lot of lost time looking for stuff that isn’t where you expect it to be. Enforcing conventions is not a limitation; when you work in a team it is indispensable.

TFFKAI — The Framework Formerly Known As Ink

Foundation for Emails comes with a boilerplate template, which is the starting point for your code. It is fully annotated, so you know how to extend it with your code. It comes with SASS/SCSS support, which is very very handy for complex projects. It also comes with its own inliner, so you don’t have to worry about converting all your CSS (or SASS/SCSS) into inline styles.

There’s a template engine behind this framework called Inky. And, just like MJML, it has custom tags that will automatically convert to HTML when it’s compiled. There are tags like <container>, <row>, <column>, which will be used to build your grid. The grid is based on a 12-column system, which allows you to subdivide your layout very accurately. Why 12? Because it is divisible by 2, 3, 4 and 6, making it very easy to make a 2-column, 3-column, 4-column, or 6-column layout.

Foundation for Emails uses Panini to compile the code. Panini is a custom library which compiles HTML pages using layouts. It supports Handlebars syntax and there are several helpers you can use to customize the behavior of components depending on where they’re being used. You can also create your own helpers if you need to and set each template’s custom variables with custom data. This is very useful if you have several templates sharing the same components.

There are several pre-built email templates available you can download, which cover many of the standard use cases for email, like newsletters and announcements. There are also a few pre-built components (with their own custom tags), including buttons, menus and callouts (which, I have to admit, I don’t see a purpose for in emails, but never mind).

A code sample from a Foundation for Emails template.

The main difference between Foundation for Emails with MJML is that Foundation for Emails defaults to desktop view, then scales for smaller screens. According to the docs, this is because many desktop clients do not support media queries and defaulting to the large screen layout makes it more compliant across email clients. That said, it only manages one breakpoint. You create the desktop version and the mobile version, and the mobile version switches under a certain number of pixels, which can be configured.

You can decide whether some components will be visible only on large or small screens using handy pre-defined classes like .hide-for-large and .show-for-large (although .hide-for-large might not be supported by all clients). You can also decide how much space a column will take by using specific classes. For example, a class of .large-6 and .small-12 on a div will make a column that occupies half the screen on desktop and the whole screen width on mobile. This allows for very specific and predictable layout results.

A preview of the same e-mail template, developed with Foundation for Emails, on Outlook 2007 (left) and iPhoneX (right).

Foundation for Emails is a bit clunkier to use than MJML, in my opinion, but it does allow for much tighter control on the layout. That makes it ideal for projects where you need to reproduce pixel-perfect designs, with very specific differences between mobile and desktop layouts.

Advantages

  • A more precise control over end results
  • Pre-built templates
  • Sass support
  • Great documentation

Disadvantages

  • The project file size is heavy and takes a lot of disk space
  • A little less intuitive to use than MJML’s pre-defined parameters on components
  • Fewer components available for custom layouts

Conclusions

Producing email templates, even less than front-end development, is not an exact science. It requires a lot of trial and error and a LOT of testing. Whatever tool you use, if you need to support old clients, then you need to test the hell out of your layouts — especially if they have even the smallest degree of complexity. For example, if you have text that needs to sit beside an image, I recommend testing with content at different lengths and see what happens in all clients. If you have text that needs to overlap an image, it can be a bit of a nightmare.

The more complex the layout and the less control you have over the layout, then the more useful it is to use a framework over hand-coding your own emails, especially if the design is handed to you by a third party and has to be implemented as-is.

I wouldn’t say that one framework is better than the other and that’s not the point of this post. Rather, I would recommend MJML and Foundation for Emails for different use cases:

  • MJML for projects that have a quick turnaround and there is flexibility in the design.
  • Foundation for Emails for projects that require tighter control over the layout and where design is super specific.

Resources and Links

  • The MJML website
  • The Foundation for Emails website
  • Litmus Email Testing
  • Email on Acid Testing
  • An interesting conversation on the Litmus forum, which was in some ways the starting point for this article.
  • Another article by James Luterek that compares these frameworks

The post Choosing a Responsive Email Framework: MJML vs. Foundation for Emails appeared first on CSS-Tricks.

What are Higher-Order Components in React?

If you have been in the React ecosystem for a while, there is a possibility that you have heard about Higher Order Components. Let’s look at a simple implementation while also trying to explain the core idea. From here you should get a good idea of how they work and even put them to use.

Why Higher-Order Components?

As you build React applications, you will run into situations where you want to share the same functionality across multiple components.

For example: you need to manage the state of currently logged in users in your application. Instead of managing that state across all of the components that need that state, you could create a higher-order component to separate the logged in user state into a container component, then pass that state to the components that will make use of it.

The components that receive state from the higher-order component will function as presentational components. State gets passed to them and they conditionally render UI based on it. They do not bother with the management of state.

Let’s see another example. Say you have three JSON files in your application. These files contain different data that will be loaded in your application in three different components. You want to give your users the ability to search the data loaded from these files. You could implement a search feature in all three of the components. This duplication may not be an issue at first, but as your application grows and more components need this functionality, the constant duplication will be cumbersome and prone to problems.

A better way forward is to create a higher-order component to handle the search functionality. With it, you can wrap the other components individually in your higher-order component.

How do Higher-Order Components Work?

The hoc Pen by Kingsley Silas Chijioke (@kinsomicrote) on CodePen.

Conclusion

Higher-Order Components do not have to be scary. After understanding the basics, you can put the concept to use by abstracting away functionalities that can be shared among different components.

More Resources

  • Higher-Order Components – React Documentation
  • React Higher Order Components in depth – by Fran Guijarro
  • Higher Order Components in React – by Chris Nwamba
  • More Examples – CodePen collection

The post What are Higher-Order Components in React? appeared first on CSS-Tricks.

Creating a Panning Effect for SVG

Earlier this month on the Animation at Work Slack, we had a discussion about finding a way to let users pan inside an SVG.

I made this demo below to show how I’d approach this question:

See the Pen Demo – SVG Panning by Louis Hoebregts (@Mamboleoo) on CodePen.

Here are the four steps to make the above demo work:

  1. Get mouse and touch events from the user
  2. Calculate the mouse offsets from its origin
  3. Save the new viewBox coordinates
  4. Handle dynamic viewport

Let’s check those steps one by one more thoroughly.

1. Mouse & Touch Events

To get the mouse or touch position, we first need to add event listeners on our SVG. We can use the Pointer Events to handle all kind of pointers (mouse/touch/stylus/…) but those events are not yet supported by all browsers. We will need to add some fallback to make sure all users will be able to drag the SVG.

// We select the SVG into the page
var svg = document.querySelector('svg'); // If browser supports pointer events
if (window.PointerEvent) { svg.addEventListener('pointerdown', onPointerDown); // Pointer is pressed svg.addEventListener('pointerup', onPointerUp); // Releasing the pointer svg.addEventListener('pointerleave', onPointerUp); // Pointer gets out of the SVG area svg.addEventListener('pointermove', onPointerMove); // Pointer is moving
} else { // Add all mouse events listeners fallback svg.addEventListener('mousedown', onPointerDown); // Pressing the mouse svg.addEventListener('mouseup', onPointerUp); // Releasing the mouse svg.addEventListener('mouseleave', onPointerUp); // Mouse gets out of the SVG area svg.addEventListener('mousemove', onPointerMove); // Mouse is moving // Add all touch events listeners fallback svg.addEventListener('touchstart', onPointerDown); // Finger is touching the screen svg.addEventListener('touchend', onPointerUp); // Finger is no longer touching the screen svg.addEventListener('touchmove', onPointerMove); // Finger is moving
}

Because we could have touch events and pointer events, we need to create a tiny function to returns to coordinates either from the first finger either from a pointer.

// This function returns an object with X & Y values from the pointer event
function getPointFromEvent (event) { var point = {x:0, y:0}; // If event is triggered by a touch event, we get the position of the first finger if (event.targetTouches) { point.x = event.targetTouches[0].clientX; point.y = event.targetTouches[0].clientY; } else { point.x = event.clientX; point.y = event.clientY; } return point;
}

Once the page is ready and waiting for any user interactions, we can start handling the mousedown/touchstart events to save the original coordinates of the pointer and create a variable to let us know if the pointer is down or not.

// This variable will be used later for move events to check if pointer is down or not
var isPointerDown = false; // This variable will contain the original coordinates when the user start pressing the mouse or touching the screen
var pointerOrigin = { x: 0, y: 0
}; // Function called by the event listeners when user start pressing/touching
function onPointerDown(event) { isPointerDown = true; // We set the pointer as down // We get the pointer position on click/touchdown so we can get the value once the user starts to drag var pointerPosition = getPointFromEvent(event); pointerOrigin.x = pointerPosition.x; pointerOrigin.y = pointerPosition.y;
}

2. Calculate Mouse Offsets

Now that we have the coordinates of the original position where the user started to drag inside the SVG, we can calculate the distance between the current pointer position and its origin. We do this for both the X and Y axis and we apply the calculated values on the viewBox.

// We save the original values from the viewBox
var viewBox = { x: 0, y: 0, width: 500, height: 500
}; // The distances calculated from the pointer will be stored here
var newViewBox = { x: 0, y: 0
}; // Function called by the event listeners when user start moving/dragging
function onPointerMove (event) { // Only run this function if the pointer is down if (!isPointerDown) { return; } // This prevent user to do a selection on the page event.preventDefault(); // Get the pointer position var pointerPosition = getPointFromEvent(event); // We calculate the distance between the pointer origin and the current position // The viewBox x & y values must be calculated from the original values and the distances newViewBox.x = viewBox.x - (pointerPosition.x - pointerOrigin.x); newViewBox.y = viewBox.y - (pointerPosition.y - pointerOrigin.y); // We create a string with the new viewBox values // The X & Y values are equal to the current viewBox minus the calculated distances var viewBoxString = `${newViewBox.x} ${newViewBox.y} ${viewBox.width} ${viewBox.height}`; // We apply the new viewBox values onto the SVG svg.setAttribute('viewBox', viewBoxString); document.querySelector('.viewbox').innerHTML = viewBoxString;
}

If you don’t feel comfortable with the concept of viewBox, I would suggest you first read this great article by Sara Soueidan.

3. Save Updated viewBox

Now that the viewBox has been updated, we need to save its new values when the user stops dragging the SVG.

This step is important because otherwise we would always calculate the pointer offsets from the original viewBox values and the user will drag the SVG from the starting point every time.

function onPointerUp() { // The pointer is no longer considered as down isPointerDown = false; // We save the viewBox coordinates based on the last pointer offsets viewBox.x = newViewBox.x; viewBox.y = newViewBox.y;
}

4. Handle Dynamic Viewport

If we set a custom width on our SVG, you may notice while dragging on the demo below that the bird is moving either faster or slower than your pointer.

See the Pen Dynamic viewport – SVG Panning by Louis Hoebregts (@Mamboleoo) on CodePen.

On the original demo, the SVG’s width is exactly matching its viewBox width. The actual size of your SVG may also be called viewport. In a perfect situation, when the user is moving their pointer by 1px, we want the viewBox to translate by 1px.

But, most of the time, the SVG has a responsive size and the viewBox will most likely not match the SVG viewport. If the SVG’s width is twice as big than the viewBox, when the user moves their pointer by 1px, the image inside the SVG will translate by 2px.

To fix this, we need to calculate the ratio between the viewBox and the viewport and apply this ratio while calculating the new viewBox. This ratio must also be updated whenever the SVG size may change.

// Calculate the ratio based on the viewBox width and the SVG width
var ratio = viewBox.width / svg.getBoundingClientRect().width;
window.addEventListener('resize', function() { ratio = viewBox.width / svg.getBoundingClientRect().width;
});

Once we know the ratio, we need to multiply the mouse offsets by the ratio to proportionally increase or reduce the offsets.

function onMouseMove (e) { [...] newViewBox.x = viewBox.x - ((pointerPosition.x - pointerOrigin.x) * ratio); newViewBox.y = viewBox.y - ((pointerPosition.y - pointerOrigin.y) * ratio); [...]
}

Here’s how this works with a smaller viewport than the viewBox width:

See the Pen Smaller viewport – SVG Panning by Louis Hoebregts (@Mamboleoo) on CodePen.

And another demo with a viewport bigger than the viewBox width:

See the Pen Bigger viewport – SVG Panning by Louis Hoebregts (@Mamboleoo) on CodePen.

[Bonus] Optimizing the code

To make our code a bit shorter, there are two very useful concepts in SVG we could use.

SVG Points

The first concept is to use SVG Points instead of basic Javascript objects to save the pointer’s positions. After creating a new SVG Point variable, we can apply some Matrix Transformation on it to convert the position relative to the screen to a position relative to the current SVG user units.

Check the code below to see how the functions getPointFromEvent() and onPointerDown() have changed.

// Create an SVG point that contains x & y values
var point = svg.createSVGPoint(); function getPointFromEvent (event) { if (event.targetTouches) { point.x = event.targetTouches[0].clientX; point.y = event.targetTouches[0].clientY; } else { point.x = event.clientX; point.y = event.clientY; } // We get the current transformation matrix of the SVG and we inverse it var invertedSVGMatrix = svg.getScreenCTM().inverse(); return point.matrixTransform(invertedSVGMatrix);
} var pointerOrigin;
function onPointerDown(event) { isPointerDown = true; // We set the pointer as down // We get the pointer position on click/touchdown so we can get the value once the user starts to drag pointerOrigin = getPointFromEvent(event);
}

By using SVG Points, you don’t even have to handle transformations applied on your SVG! Compare the following two examples where the first is broken when a rotation is applied on the SVG and the second example uses SVG Points.

See the Pen Demo + transformation – SVG Panning by Louis Hoebregts (@Mamboleoo) on CodePen.

See the Pen Demo Bonus + transform – SVG Panning by Louis Hoebregts (@Mamboleoo) on CodePen.

SVG Animated Rect

The second unknown concept in SVG we can use to shorten our code, is the usage of Animated Rect.

Because the viewBox is actually considered as an SVG Rectangle (x, y, width, height), we can create a variable from its base value that will automatically update the viewBox if we update this variable.

See how easier it is now to update the viewBox of our SVG!

// We save the original values from the viewBox
var viewBox = svg.viewBox.baseVal; function onPointerMove (event) { if (!isPointerDown) { return; } event.preventDefault(); // Get the pointer position as an SVG Point var pointerPosition = getPointFromEvent(event); // Update the viewBox variable with the distance from origin and current position // We don't need to take care of a ratio because this is handled in the getPointFromEvent function viewBox.x -= (pointerPosition.x - pointerOrigin.x); viewBox.y -= (pointerPosition.y - pointerOrigin.y);
}

And here is the final demo. See how much shorter the code is now? 😀

See the Pen Demo Bonus – SVG Panning by Louis Hoebregts (@Mamboleoo) on CodePen.

Conclusion

This solution is definitely not the only way to go to handle such behavior. If you are already using a library to deal with your SVGs, it may already have a built-in function to handle it.

I hope this article may help you to understand a bit more how powerful SVG can be! Feel free to contribute to the code by commenting with your ideas or alternatives to this solution.

Credits

  • Bird designed by Freepik
  • A big thanks to Blake for his precious help and all the nice folks from the AAW Slack for their feedback.

The post Creating a Panning Effect for SVG appeared first on CSS-Tricks.

Hey hey `font-display`

Y’all know about font-display? It’s pretty great. It’s a CSS property that you can use within @font-face blocks to control how, visually, that font loads. Font loading is really pretty damn complicated. Here’s a guide from Zach Leatherman to prove it, which includes over 10 font loading strategies, including strategies that involve critical inline CSS of subsets of fonts combined with loading the rest of the fonts later through JavaScript. It ain’t no walk in the park.

Using font-display is kinda like a walk in the park though. It’s just a single line of CSS. It doesn’t solve everything that Zach’s more exotic demos do, but it can go a long way with that one line. It’s notable to bring up right now, as support has improved a lot lately. It’s now in Firefox 58+, Chrome 60+, Safari 11.1+, iOS 11.3+, and Chrome on Android 64+. Pretty good.

What do you get from it? The ability to control font-display for the Masses by Jeremy Wagner

  • If you really dislike FOUT, font-display: optional might be your jam by me
  • Reminder:

    FOUT = Flash of Unstyled Text
    FOIT = Flash of Invisible Text

    Neither is great. In a perfect world, our custom fonts just show up immediately. But since that’s not a practical possibility, we pick based on our priorities.

    The best resource out there about it is Monica Dinculescu’s explainer page:

    i’d summarize those values choices like this:

    • If you’re OK with FOUT, you’re probably best off with font-display: swap; which will display a fallback font fairly fast, but swap in your custom font when it loads.
    • If you’re OK with FOIT, you’re probably best off with font-display: block; which is fairly similar to current browser behavior, where it shows nothing as it waits for the custom font, but will eventually fall back.
    • If you only want the custom font to show at all if it’s there immediately, font-display: optional; is what you want. It’ll still load in the background and be there next page load probably.

    Those are some pretty decent options for a single line of CSS. But again, remember if you’re running a major text-heavy site with custom fonts, Zach’s guide can help you do more.

    I’d almost go out on a limb and say: every @font-face block out there should have a font-display property. With the only caveat being you’re doing something exotic and for some reason want the browser default behavior.

    Wanna hear something quite unfortunate? We already mentioned font-display: block;. Wouldn’t you think it, uh, well, blocked the rendering of text until the custom font loads? It doesn’t. It’s still got a swap period. It would be the perfect thing for something like icon fonts where the icon (probably) has no meaning unless the custom font loads. Alas, there is no font-display solution for that.

    And, hey gosh, wouldn’t it be nice if Google Fonts allowed us to use it?

    The post Hey hey `font-display` appeared first on CSS-Tricks.