- Professional CSS3
- Piotr Sikora
- 644字
- 2021-07-02 16:39:39
Floating elements
Floating boxes are the most used in modern layouts. The theory of floating boxes was used especially in grid systems and inline lists in CSS frameworks. For example, class and mixin inline lists (in the Zurb Foundation framework) are based on floats.
Possibilities of floating elements
Elements can be floated to the left and right side. Of course, there is a method to reset floats too. The possible values are as follows:
float: left; // will float element to left float: right; // will float element to right float: none; // will reset float
Most known floating problems
When you are using floating elements, you can have some issues. The most known problems with floated elements are as follows:
- Too big elements (because of width, margin left/right, padding left/right, and badly counted width, which is based on the box model)
- Not cleared floats
All of these problems provide specific effects, which you can easily recognize and then fix.
Elements which are too big can be recognized when they are not in one line, as they should be. What you should check first is if the box-sizing: border-box is applied, and then check width, padding, and margin.
You can easily recognize floats that are not cleared when the floating structure of some elements from next container are floated. This means that you have no clear fix in your floating container.
Defining clear fix/class/mixins
When I started developing HTML and CSS code, there was a method to clear the floats with .cb
or .clear
classes, both of which were defined as follows:
.clearboth, .cb { clear: both }
This element was added in a container right after all the floated elements. This is important to remember about clearing the floats because containers that contains floating elements won't inherit the height of the highest floating element (which will have a height equal to 0
),for example:
<div class="container"> <div class="float"> … content ... </div> <div class="float"> … content ... </div> <div class="clearboth"></div> </div>
CSS looks like the following:
.float { width: 100px; height: 100px; float: left; } .clearboth { clear: both }
Nowadays, there is a better and faster way to clear floats. You can do this with the clear fix
element, which can be defined as follows:
.clearfix:after { content: ""; visibility: hidden; display: block; height: 0; clear: both; }
And you can use it in HTML code:
<div class="container clearfix"> <div class="float"> ... content ... </div> <div class="float"> ... content ... </div> </div> </div>
The main reason to switch on clear fix
is that you save one tag (with the clearboth
class). Recommended usage is based on the clear fix
mixin, which you can define in SASS as follows:
=clear fix &:after content: "" visibility: hidden display: block height: 0 clear: both
Therefore, every time you need to clear floating in some container, you need to invoke it. For example, let us take the previous code:
<div class="container"> <div class="float"> … content ... </div> <div class="float"> … content ... </div> </div>
The container can be described as follows:
.container +clear fix
Example of using floating elements
The most known usage of float elements is grids. A grid is mainly used to structure the data displayed on a web page. In this chapter, let's check just a short draft of a grid. In the upcoming chapters, we will focus on automatization of creating the grid with mixins.
Let us create some HTML code:
<div class="row"> <div class="column_1of2"> Lorem </div> <div class="column_1of2"> Lorem </div> </div> <div class="row"> <div class="column_1of3"> Lorem </div> <div class="column_1of3"> Lorem </div> <div class="column_1of3"> Lorem </div> </div> <div class="row"> <div class="column_1of4"> Lorem </div> <div class="column_1of4"> Lorem </div> <div class="column_1of4"> Lorem </div> <div class="column_1of4"> Lorem </div> </div>
And also create some SASS code:
* box-sizing: border-box =clear fix &:after content: "" visibility: hidden display: block height: 0 clear: both .row +clear fix .column_1of2 background: orange width: 50% float: left &:nth-child(2n) background: red .column_1of3 background: orange width: (100% / 3) float: left &:nth-child(2n) background: red .column_1of4 background: orange width: 25% float: left &:nth-child(2n) background: red
The final effect is as follows:

As you can see, we created a structure of a basic grid. In places where HTML code is placed Lorem
here is a full lorem ipsum
to illustrate the grid system.
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