I decided to start a series called CSS power-up! I will be collecting small posts about neat CSS features. There's one specifically that I was very impressed by. Not only for how intuitive it is but also for its widespread browser support.
Tired of having overly priced note-taking apps, or free ones that don't offer what I need, I decided to create my own! That's why I started a side project that led to rediscovering an interesting CSS property.
It all started with Slate.js
, which provides a library to build rich text editors. One feature I was looking for in my app, was the ability to add code blocks. I soon found a plugin called slate-code
that does it for me. How convenient! After fiddling with it a bit here's the result:
Now this looks fine but, I'm sure you noticed something is missing. Where is the line count ? Armed with patience I decided to go down the rabbit hole, convinced it would be a painful journey. At first I thought about using some sort of index reference to each line and display that on the side. But handling deleting and insertion of lines seemed overly complicated π€.
Then I remembered that you could do that very intuitively with CSS only! I was thrilled π! The way it works is by creating a named counter and specifying which CSS class increments that counter. On top of that you also have access to the counter value that you can display as content
.
Let's dig into it. First let's define the class of the container of the code block.
.code {
background: #f7f9fa;
border: 1px solid #e6e8eb;
font-family: "Lucida Console",Monaco,monospace;
overflow: auto;
padding: 8px;
white-space: pre;
counter-reset: line;
}
With counter-reset: line
we are defining and initializing a counter named line
with the value 0.
Now we need to determine which class will be in charge of incrementing the counter. We use the counter-increment
property for that and give it the value of the counter name we want to increment, in our case line
.
To finish up we also want to display the counter value. Using counter(line)
with the content
property that's exactly what we get. As an extra you can add the -webkit-user-select: none
to prevent user from selecting the counter values. This is helpful when you want to copy a whole code block.
.code-line::before {
counter-increment: line;
content: counter(line);
-webkit-user-select: none;
font-size: 10px;
color: grey;
margin-right: 10px;
text-align: right;
display: inline-block;
width: 18px;
}
And the result is the following:
The rest of the styling is pretty arbitrary and up to you. As you can see it was quite easy to add something as simple as a line count. You can find the full reference here. At first I was very thrilled by the simplicity of this method then I remembered that I had to check browser support.
π What a victory! We went from panicking about ways to implement a line counter to having a simple CSS property that is widely supported. I hope you found this as interesting as I did. Is there any not-so-popular CSS property that left you "wowed" ? Have you used the line counter before ?
If you want to see a live demo, you can find one here.
π Hi, Iβm Gabri! I love innovation and lead R&D at Hutch. I also love React, Javascript and Machine Learning (among a million other things). You can follow me on twitter @gabrielecimato and on GitHub @Gabri3l. Leave a comment or send a DM on Twitter if you have any questions!
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