This article was originally published on 05 October, 2012 at Trezy.com.
Pure CSS tooltips have been a thing for a while now but all of the solutions I've found have had limitations. After reading through Louis Lazaris's article Pure CSS Tool Tips Revisited over at ImpressiveWebs, I decided to make a few modifications of my own to his design.
Check Out the Demo
The Problem
Louis's design broke some of the boundaries but still had some limitations. These were my goals:
Multiline
Louis makes the argument that tooltips are only supposed to contain a small amount of information, eliminating the need for multiline tooltips. I agree with him to an extent, but I still think there are cases in which you would want a multiline tooltip. In my example, I am creating an error message rather than your average tooltip. I wanted my first line to be only the error type, then all of the following lines would contain the error message.
IE8 Compatible
This was a big one since the company I'm doing this project for requires it. Fortunately we only have to support IE8, Firefox, and Webkit. Keep in mind, however, that this also means I don't know how this code will react in IE7 and below.
No Extra HTML
Some other pure CSS tooltip solutions use extra elements, like placeholder spans or divs. I wanted to be able to pull in all of the information I needed without any extra elements. I bend the extra HTML rule a little bit since we do use an element's attributes to populate the tooltip but I think I can still live with myself.
The Solution
If you check out the pen, you may notice the custom data- attributes on the link. The data-tooltip attribute is binary, meaning it's either set or it's not, just like required. I'll be using jQuery to create and populate the other two attributes in the final project but for now we'll just use some bunk data.
Pseudo-classes and Uncommon Attributes
Most pseudo-classes describe some state of an element, i.e. :hover applies when the element is being hovered, :focus applies to form elements that are in focus, :disabled applies to elements that are disabled, etc. However, :before and :after are a little different. They are used to prepend and append, respectively, content to an element. For example you could use .emailAddress:before to append a label to the internal node of every element with a class of emailAddress.
You have probably seen most of this CSS before, though we're using a couple of pretty uncommon attributes. The content attribute only works with the :before and :after pseudo-classes. It determines what to prepend/append to the element. In this case we're using a pretty cool argument called attr(x). It allows you to use the value from any attribute applied to the element as the content of the prepended/appended element. In our case we used the custom data- attributes we set earlier.
The white-space is another strange one. It's used to determine how white space (spaces and returns) should be handled inside of an element. We used white-space:pre-wrap; so that the spaces inside the content attribute would be preserved, specifically the \A which is a Unicode carriage return, pretty much the only way to ensure that the line breaks where we want.
Positioning
This was the most important point to allowing multiline tooltips. Some previous solutions have used percentage positioning, some used pixel positioning, but they all used the top and left attributes. However these always break if you have more than one line so they are often used with white-space:nowrap;.
Instead of positioning negatively based on the top position of the element like Louis did, I set the top position of the tooltip to zero so it would line up with the top of the element, then gave the tooltip a margin-top. In my example, I'm placing the tooltip on a link so I set the bottom margin to 1em, ensuring the margin would always be the same height as my text. This may need to be adjusted depending on your line-height.
If you're not positioning the tooltip on a line of text then you can also set your margin to match the height of a static height element, or use some jQuery magic to adjust it.
Wrapping It Up
The rest of this code is pretty standard stuff. One other peculiar thing we're doing here is using the :before to create the arrow on the bottom of the tooltip. Louis's article explains that part a bit and there are plenty of other tutorials on creating shapes using divs and borders so I won't cover that.
I've tested this in all of the necessary browsers (IE8+, Firefox, and Google Chrome) and haven't seen any issues yet. If you run into an issue or have a recommendation for making it even better, let me know in the comments! I'll do another tutorial in the future about how to make this guy extensible using jQuery. 😉
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