全局CSS样式

深入了解 TWUI 底层结构的关键部分，包括我们让 web 开发变得更好、更快、更强壮的最佳实践。

HTML5 doctype-HTML页面文档头

TWUI 使用到的某些 HTML 元素和 CSS 属性需要将页面设置为 HTML5 文档类型。在你项目中的每个页面都要参照下面的格式进行设置。

<!doctype html>
<html lang="zh-CN">
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8"/>
<meta http-equiv="X-UA-Compatible" content="IE=edge"/>
<title>页面标题</title>
<meta name="Keywords" content="页面关键字"/> 
<meta name="Description" content="页面关键字描述"/>
<link rel="stylesheet" href="css/样式.css" type="text/css" media="screen" />
<link rel="shortcut icon" type="image/x-icon"  href="http://www.xxx.com/favicon.ico"/>
</head>
  ...
</html>

css 重置(TODO：base.css有待分离)

重置浏览器的默认样式，也就是覆盖掉浏览器的默认样式,使得组件基础样式表现一致

为了确保引入的重置样式正确生效，引入以下的重置样式时，必须为第一个<link>引入. 点击查看base.css

<link rel="stylesheet" href="css/base.css" type="text/css" media="screen"/>

因oa项目的需求问题暂不使用normalize.css作为css重置样式

页面背景，字体与链接

TWUI 文字排版、链接样式设置了基本的全局样式。分别是：

设置body的背景色为 background-color: #fff;
使用@font-family-base, @font-size-base,和 @line-height-base 的less变量作为排版的基本参数
为所有链接设置了基本颜色 @link-color 并且当链接处于 :hover状态时才添加下划线

这些样式都能在 scaffolding.less文件中找到对应的源码.

标题

HTML 中的所有标题标签，, <h1> ~ <h6>, 均可使用.另外，还提供了.h1 到 .h6 类，为的是给内联（inline）属性的文本赋予标题的样式。

h1. TWUI heading	Semibold 36px
h2. TWUI heading	Semibold 30px
h3. TWUI heading	Semibold 24px
h4. TWUI heading	Semibold 18px
h5. TWUI heading	Semibold 14px
h6. TWUI heading	Semibold 12px

<h1>h1. TWUI heading</h1>
<h2>h2. TWUI heading</h2>
<h3>h3. TWUI heading</h3>
<h4>h4. TWUI heading</h4>
<h5>h5. TWUI heading</h5>
<h6>h6. TWUI heading</h6>

文本

页面中，文本样式，使用字体大小.fontSize12 到 .fontSizeXX 类(xx为字号)，.bold(粗体)，给内联（inline）属性的文本赋予标题的样式。

.fontSize12 普通文本	Semibold 12px
.fontSize12 .bold 普通文本	Semibold 12px
.fontSize14 普通文本	Semibold 14px
.fontSize14 .bold 普通文本	Semibold 14px
.fontSize16 普通文本	Semibold 16px
.fontSize16 .bold 普通文本	Semibold 16px

<span class="fontSize12">.fontSize12 普通文本</span>
<span class="fontSize12 bold">.fontSize12 .bold 普通文本</span>
<span class="fontSize14">.fontSize14 普通文本</span>
<span class="fontSize14 bold">.fontSize14 .bold 普通文本</span>
<span class="fontSize16">.fontSize16 普通文本</span>
<span class="fontSize16 bold">.fontSize16 .bold 普通文本</span>

带链接文本

页面中，a默认不带下划线，如需要下划线要添加.textDecoration类，添加颜色使用.linkBlue(蓝色链接)，.linkRed(红色链接)

规范手册.doc	全局普通文本a链接
规范手册.doc	全局普通文本a链接,带下划线
规范手册.doc [下载][删除]	全局普通文本a链接,带颜色区分链接
规范手册.doc [下载][删除]	全局普通文本a链接,带颜色区分链接,按需添加下划线

<a href="#">规范手册.doc</a>
<a href="#" class="textDecoration">规范手册.doc</a>
<a href="#">规范手册.doc</a><a href="#" class="linkBlue">[下载]</a><a href="#" class="linkRed">[删除]</a>
<a href="#">规范手册.doc</a><a href="#" class="linkBlue textDecoration">[下载]</a><a href="#" class="linkRed">[删除]</a>

页面主体

Bootstrap 将全局font-size 设置为14px，line-height 设置为1.428。这些属性直接赋予<body>元素和所有段落元素。另外，<p>元素还被设置了等于 1/2 行高（即 10px）的底部外边距（margin）

twui是一个来源于bootstrap的前端OAui框架twui是一个来源于bootstrap的前端OAui框架twui是一个来源于bootstrap的前端OAui框架twui是一个来源于bootstrap的前端OAui框架twui是一个来源于bootstrap的前端OAui框架twui是一个来源于bootstrap的前端OAui框架twui是一个来源于bootstrap的前端OAui框架

使用 Less 工具构建

variables.less文件中定义的两个 Less 变量决定了排版@font-size-base 和 @line-height-base。第一个变量定义了全局 font-size 基准，第二个变量是 line-height 基准。我们使用这些变量和一些简单的公式计算出其它所有页面元素的 margin、 padding 和 line-height。自定义这些变量即可改变 Bootstrap 的默认样式。

对齐

通过文本对齐类，可以简单方便的将文字重新对齐。

左对齐的文本.

居中对齐的文本

右对齐的文本

左右对称的文本左右对称的文本左右对称的文本左右对称的文本左右对称的文本左右对称的文本左右对称的文本左右对称的文本左右对称的文本左右对称的文本左右对称的文本左右对称的文本左右对称的文本左右对称的文本左右对称的文本左右对称的文本左右对称的文本

不换行文本

<p class="text-left">左对齐的文本.</p>
<p class="text-center">居中对齐的文本</p>
<p class="text-right">右对齐的文本</p>
<p class="text-justify">左右对称的文本</p>
<p class="text-nowrap">不换行文本</p>

列表

基本无序列表

不使用浏览器默认样式的列表,使用.listXX(XX的范围是01开始)定义

·Lorem ipsum dolor sit amet
·Consectetur adipiscing elit
·Integer molestie lorem at massa
·Facilisis in pretium nisl aliquet
·Nulla volutpat aliquam velit
·Faucibus porta lacus fringilla vel
·Aenean sit amet erat nunc
·Eget porttitor lorem

<ul class="list01">
  <li>·文本内容</li>
</ul>

无序列表的其他组件，将会在htmlcss组件列出，其他列表暂不列出

Inline

Wrap inline snippets of code with <code>.

For example, <section> should be wrapped as inline.

For example, <code>&lt;section&gt;</code> should be wrapped as inline.

User input

Use the <kbd> to indicate input that is typically entered via keyboard.

To switch directories, type cd followed by the name of the directory.
To edit settings, press ctrl + ,

To switch directories, type <kbd>cd</kbd> followed by the name of the directory.

Basic block

Use <pre> for multiple lines of code. Be sure to escape any angle brackets in the code for proper rendering.

<p>Sample text here...</p>

<pre>&lt;p&gt;Sample text here...&lt;/p&gt;</pre>

You may optionally add the .pre-scrollable class, which will set a max-height of 350px and provide a y-axis scrollbar.

Variables

For indicating variables use the <var> tag.

y = mx + b

<var>y</var> = <var>m</var><var>x</var> + <var>b</var>

Sample output

For indicating blocks sample output from a program use the <samp> tag.

This text is meant to be treated as sample output from a computer program.

<samp>This text is meant to be treated as sample output from a computer program.</samp>

Basic example

For basic styling—light padding and only horizontal dividers—add the base class .table to any <table>. It may seem super redundant, but given the widespread use of tables for other plugins like calendars and date pickers, we've opted to isolate our custom table styles.

#	First Name	Last Name	Username
1	Mark	Otto	@mdo
2	Jacob	Thornton	@fat
3	Larry	the Bird	@twitter

<table class="table">
  ...
</table>

Striped rows

Use .table-striped to add zebra-striping to any table row within the <tbody>.

Cross-browser compatibility

Striped tables are styled via the :nth-child CSS selector, which is not available in Internet Explorer 8.

#	First Name	Last Name	Username
1	Mark	Otto	@mdo
2	Jacob	Thornton	@fat
3	Larry	the Bird	@twitter

<table class="table table-striped">
  ...
</table>

Bordered table

Add .table-bordered for borders on all sides of the table and cells.

#	First Name	Last Name	Username
1	Mark	Otto	@mdo
1	Mark	Otto	@TwBootstrap
2	Jacob	Thornton	@fat
3	Larry the Bird		@twitter

<table class="table table-bordered">
  ...
</table>

Hover rows

Add .table-hover to enable a hover state on table rows within a <tbody>.

#	First Name	Last Name	Username
1	Mark	Otto	@mdo
2	Jacob	Thornton	@fat
3	Larry the Bird		@twitter

<table class="table table-hover">
  ...
</table>

Condensed table

Add .table-condensed to make tables more compact by cutting cell padding in half.

#	First Name	Last Name	Username
1	Mark	Otto	@mdo
2	Jacob	Thornton	@fat
3	Larry the Bird		@twitter

<table class="table table-condensed">
  ...
</table>

Contextual classes

Use contextual classes to color table rows or individual cells.

Class	Description
`.active`	Applies the hover color to a particular row or cell
`.success`	Indicates a successful or positive action
`.info`	Indicates a neutral informative change or action
`.warning`	Indicates a warning that might need attention
`.danger`	Indicates a dangerous or potentially negative action

#	Column heading	Column heading	Column heading
1	Column content	Column content	Column content
2	Column content	Column content	Column content
3	Column content	Column content	Column content
4	Column content	Column content	Column content
5	Column content	Column content	Column content
6	Column content	Column content	Column content
7	Column content	Column content	Column content
8	Column content	Column content	Column content
9	Column content	Column content	Column content

<!-- On rows -->
<tr class="active">...</tr>
<tr class="success">...</tr>
<tr class="warning">...</tr>
<tr class="danger">...</tr>
<tr class="info">...</tr>

<!-- On cells (`td` or `th`) -->
<tr>
  <td class="active">...</td>
  <td class="success">...</td>
  <td class="warning">...</td>
  <td class="danger">...</td>
  <td class="info">...</td>
</tr>

Responsive tables

Create responsive tables by wrapping any .table in .table-responsive to make them scroll horizontally on small devices (under 768px). When viewing on anything larger than 768px wide, you will not see any difference in these tables.

Firefox and fieldsets

Firefox has some awkward fieldset styling involving width that interferes with the responsive table. This cannot be overriden without a Firefox-specific hack that we don't provide in Bootstrap:

@-moz-document url-prefix() {
  fieldset { display: table-cell; }
}

For more information, read this Stack Overflow answer.

#	Table heading	Table heading	Table heading	Table heading	Table heading	Table heading
1	Table cell	Table cell	Table cell	Table cell	Table cell	Table cell
2	Table cell	Table cell	Table cell	Table cell	Table cell	Table cell
3	Table cell	Table cell	Table cell	Table cell	Table cell	Table cell

#	Table heading	Table heading	Table heading	Table heading	Table heading	Table heading
1	Table cell	Table cell	Table cell	Table cell	Table cell	Table cell
2	Table cell	Table cell	Table cell	Table cell	Table cell	Table cell
3	Table cell	Table cell	Table cell	Table cell	Table cell	Table cell

<div class="table-responsive">
  <table class="table">
    ...
  </table>
</div>

Basic example

Individual form controls automatically receive some global styling. All textual <input>, <textarea>, and <select> elements with .form-control are set to width: 100%; by default. Wrap labels and controls in .form-group for optimum spacing.

<form role="form">
  <div class="form-group">
    <label for="exampleInputEmail1">Email address</label>
    <input type="email" class="form-control" id="exampleInputEmail1" placeholder="Enter email">
  </div>
  <div class="form-group">
    <label for="exampleInputPassword1">Password</label>
    <input type="password" class="form-control" id="exampleInputPassword1" placeholder="Password">
  </div>
  <div class="form-group">
    <label for="exampleInputFile">File input</label>
    <input type="file" id="exampleInputFile">
    <p class="help-block">Example block-level help text here.</p>
  </div>
  <div class="checkbox">
    <label>
      <input type="checkbox"> Check me out
    </label>
  </div>
  <button type="submit" class="btn btn-default">Submit</button>
</form>

Don't mix form groups with input groups

Do not mix form groups directly with input groups. Instead, nest the input group inside of the form group.

Inline form

Add .form-inline to your <form> for left-aligned and inline-block controls. This only applies to forms within viewports that are at least 768px wide.

Requires custom widths

Inputs, selects, and textareas are 100% wide by default in Bootstrap. To use the inline form, you'll have to set a width on the form controls used within.

Always add labels

Screen readers will have trouble with your forms if you don't include a label for every input. For these inline forms, you can hide the labels using the .sr-only class.

<form class="form-inline" role="form">
  <div class="form-group">
    <label class="sr-only" for="exampleInputEmail2">Email address</label>
    <input type="email" class="form-control" id="exampleInputEmail2" placeholder="Enter email">
  </div>
  <div class="form-group">
    <label class="sr-only" for="exampleInputPassword2">Password</label>
    <input type="password" class="form-control" id="exampleInputPassword2" placeholder="Password">
  </div>
  <div class="checkbox">
    <label>
      <input type="checkbox"> Remember me
    </label>
  </div>
  <button type="submit" class="btn btn-default">Sign in</button>
</form>

Horizontal form

Use Bootstrap's predefined grid classes to align labels and groups of form controls in a horizontal layout by adding .form-horizontal to the form. Doing so changes .form-groups to behave as grid rows, so no need for .row.

<form class="form-horizontal" role="form">
  <div class="form-group">
    <label for="inputEmail3" class="col-sm-2 control-label">Email</label>
    <div class="col-sm-10">
      <input type="email" class="form-control" id="inputEmail3" placeholder="Email">
    </div>
  </div>
  <div class="form-group">
    <label for="inputPassword3" class="col-sm-2 control-label">Password</label>
    <div class="col-sm-10">
      <input type="password" class="form-control" id="inputPassword3" placeholder="Password">
    </div>
  </div>
  <div class="form-group">
    <div class="col-sm-offset-2 col-sm-10">
      <div class="checkbox">
        <label>
          <input type="checkbox"> Remember me
        </label>
      </div>
    </div>
  </div>
  <div class="form-group">
    <div class="col-sm-offset-2 col-sm-10">
      <button type="submit" class="btn btn-default">Sign in</button>
    </div>
  </div>
</form>

Supported controls

Examples of standard form controls supported in an example form layout.

Inputs

Most common form control, text-based input fields. Includes support for all HTML5 types: text, password, datetime, datetime-local, date, month, time, week, number, email, url, search, tel, and color.

Type declaration required

Inputs will only be fully styled if their type is properly declared.

<input type="text" class="form-control" placeholder="Text input">

Input groups

To add integrated text or buttons before and/or after any text-based <input>, check out the input group component.

Textarea

Form control which supports multiple lines of text. Change rows attribute as necessary.

<textarea class="form-control" rows="3"></textarea>

Checkboxes and radios

Checkboxes are for selecting one or several options in a list, while radios are for selecting one option from many.

A checkbox or radio with the disabled attribute will be styled appropriately. To have the <label> for the checkbox or radio also display a "not-allowed" cursor when the user hovers over the label, add the .disabled class to your .radio, .radio-inline, .checkbox, .checkbox-inline, or <fieldset>.

Default (stacked)

<div class="checkbox">
  <label>
    <input type="checkbox" value="">
    Option one is this and that&mdash;be sure to include why it's great
  </label>
</div>
<div class="checkbox disabled">
  <label>
    <input type="checkbox" value="" disabled>
    Option two is disabled
  </label>
</div>

<div class="radio">
  <label>
    <input type="radio" name="optionsRadios" id="optionsRadios1" value="option1" checked>
    Option one is this and that&mdash;be sure to include why it's great
  </label>
</div>
<div class="radio">
  <label>
    <input type="radio" name="optionsRadios" id="optionsRadios2" value="option2">
    Option two can be something else and selecting it will deselect option one
  </label>
</div>
<div class="radio disabled">
  <label>
    <input type="radio" name="optionsRadios" id="optionsRadios3" value="option3" disabled>
    Option three is disabled
  </label>
</div>

Inline checkboxes and radios

Use the .checkbox-inline or .radio-inline classes on a series of checkboxes or radios for controls that appear on the same line.

<label class="checkbox-inline">
  <input type="checkbox" id="inlineCheckbox1" value="option1"> 1
</label>
<label class="checkbox-inline">
  <input type="checkbox" id="inlineCheckbox2" value="option2"> 2
</label>
<label class="checkbox-inline">
  <input type="checkbox" id="inlineCheckbox3" value="option3"> 3
</label>

<label class="radio-inline">
  <input type="radio" name="inlineRadioOptions" id="inlineRadio1" value="option1"> 1
</label>
<label class="radio-inline">
  <input type="radio" name="inlineRadioOptions" id="inlineRadio2" value="option2"> 2
</label>
<label class="radio-inline">
  <input type="radio" name="inlineRadioOptions" id="inlineRadio3" value="option3"> 3
</label>

Selects

Use the default option, or add multiple to show multiple options at once.

<select class="form-control">
  <option>1</option>
  <option>2</option>
  <option>3</option>
  <option>4</option>
  <option>5</option>
</select>

<select multiple class="form-control">
  <option>1</option>
  <option>2</option>
  <option>3</option>
  <option>4</option>
  <option>5</option>
</select>

Static control

When you need to place plain text next to a form label within a horizontal form, use the .form-control-static class on a <p>.

<form class="form-horizontal" role="form">
  <div class="form-group">
    <label class="col-sm-2 control-label">Email</label>
    <div class="col-sm-10">
      <p class="form-control-static">email@example.com</p>
    </div>
  </div>
  <div class="form-group">
    <label for="inputPassword" class="col-sm-2 control-label">Password</label>
    <div class="col-sm-10">
      <input type="password" class="form-control" id="inputPassword" placeholder="Password">
    </div>
  </div>
</form>

Input focus

We remove the default outline styles on some form controls and apply a box-shadow in its place for :focus.

Demo `:focus` state

The above example input uses custom styles in our documentation to demonstrate the :focus state on a .form-control.

Disabled inputs

Add the disabled boolean attribute on an input to prevent user input and trigger a slightly different look.

<input class="form-control" id="disabledInput" type="text" placeholder="Disabled input here..." disabled>

Disabled fieldsets

Add the disabled attribute to a <fieldset> to disable all the controls within the <fieldset> at once.

Caveat about link functionality of `<a>`

Our styles use pointer-events: none to try to disable the link functionality of <a class="btn btn-*"> buttons in this case, but that CSS property is not yet standardized and isn't fully supported in Opera 18 and below, or in Internet Explorer 11. So to be safe, use custom JavaScript to disable such links.

Cross-browser compatibility

While Bootstrap will apply these styles in all browsers, Internet Explorer 9 and below don't actually support the disabled attribute on a <fieldset>. Use custom JavaScript to disable the fieldset in these browsers.

<form role="form">
  <fieldset disabled>
    <div class="form-group">
      <label for="disabledTextInput">Disabled input</label>
      <input type="text" id="disabledTextInput" class="form-control" placeholder="Disabled input">
    </div>
    <div class="form-group">
      <label for="disabledSelect">Disabled select menu</label>
      <select id="disabledSelect" class="form-control">
        <option>Disabled select</option>
      </select>
    </div>
    <div class="checkbox">
      <label>
        <input type="checkbox"> Can't check this
      </label>
    </div>
    <button type="submit" class="btn btn-primary">Submit</button>
  </fieldset>
</form>

Readonly inputs

Add the readonly boolean attribute on an input to prevent user input and style the input as disabled.

<input class="form-control" type="text" placeholder="Readonly input here…" readonly>

Validation states

Bootstrap includes validation styles for error, warning, and success states on form controls. To use, add .has-warning, .has-error, or .has-success to the parent element. Any .control-label, .form-control, and .help-block within that element will receive the validation styles.

<div class="form-group has-success">
  <label class="control-label" for="inputSuccess1">Input with success</label>
  <input type="text" class="form-control" id="inputSuccess1">
</div>
<div class="form-group has-warning">
  <label class="control-label" for="inputWarning1">Input with warning</label>
  <input type="text" class="form-control" id="inputWarning1">
</div>
<div class="form-group has-error">
  <label class="control-label" for="inputError1">Input with error</label>
  <input type="text" class="form-control" id="inputError1">
</div>

With optional icons

You can also add optional feedback icons with the addition of .has-feedback and the right icon.

Icons, labels, and input groups

Manual positioning of feedback icons is required for inputs without a label and for input groups with an add-on on the right. You are strongly encouraged to provide labels for all inputs for accessibility reasons. If you wish to prevent labels from being displayed, hide them with the sr-only class. If you must do without labels, adjust the top value of the feedback icon. For input groups, adjust the right value to an appropriate pixel value depending on the width of your addon.

<div class="form-group has-success has-feedback">
  <label class="control-label" for="inputSuccess2">Input with success</label>
  <input type="text" class="form-control" id="inputSuccess2">
  <span class="glyphicon glyphicon-ok form-control-feedback"></span>
</div>
<div class="form-group has-warning has-feedback">
  <label class="control-label" for="inputWarning2">Input with warning</label>
  <input type="text" class="form-control" id="inputWarning2">
  <span class="glyphicon glyphicon-warning-sign form-control-feedback"></span>
</div>
<div class="form-group has-error has-feedback">
  <label class="control-label" for="inputError2">Input with error</label>
  <input type="text" class="form-control" id="inputError2">
  <span class="glyphicon glyphicon-remove form-control-feedback"></span>
</div>

Optional icons in horizontal and inline forms

<form class="form-horizontal" role="form">
  <div class="form-group has-success has-feedback">
    <label class="control-label col-sm-3" for="inputSuccess3">Input with success</label>
    <div class="col-sm-9">
      <input type="text" class="form-control" id="inputSuccess3">
      <span class="glyphicon glyphicon-ok form-control-feedback"></span>
    </div>
  </div>
</form>

<form class="form-inline" role="form">
  <div class="form-group has-success has-feedback">
    <label class="control-label" for="inputSuccess4">Input with success</label>
    <input type="text" class="form-control" id="inputSuccess4">
    <span class="glyphicon glyphicon-ok form-control-feedback"></span>
  </div>
</form>

Optional icons with hidden `.sr-only` labels

For form controls with no visible label, add the .sr-only class on the label. Bootstrap will automatically adjust the position of the icon once it's been added.

<div class="form-group has-success has-feedback">
  <label class="control-label sr-only" for="inputSuccess5">Hidden label</label>
  <input type="text" class="form-control" id="inputSuccess5">
  <span class="glyphicon glyphicon-ok form-control-feedback"></span>
</div>

Control sizing

Set heights using classes like .input-lg, and set widths using grid column classes like .col-lg-*.

Height sizing

Create taller or shorter form controls that match button sizes.

<input class="form-control input-lg" type="text" placeholder=".input-lg">
<input class="form-control" type="text" placeholder="Default input">
<input class="form-control input-sm" type="text" placeholder=".input-sm">

<select class="form-control input-lg">...</select>
<select class="form-control">...</select>
<select class="form-control input-sm">...</select>

Horizontal form group sizes

Quickly size labels and form controls within .form-horizontal by adding .form-group-lg or .form-group-sm.

<form class="form-horizontal" role="form">
  <div class="form-group form-group-lg">
    <label class="col-sm-2 control-label" for="formGroupInputLarge">Large label</label>
    <div class="col-sm-10">
      <input class="form-control" type="text" id="formGroupInputLarge" placeholder="Large input">
    </div>
  </div>
  <div class="form-group form-group-sm">
    <label class="col-sm-2 control-label" for="formGroupInputSmall">Small label</label>
    <div class="col-sm-10">
      <input class="form-control" type="text" id="formGroupInputSmall" placeholder="Small input">
    </div>
  </div>
</form>

Column sizing

Wrap inputs in grid columns, or any custom parent element, to easily enforce desired widths.

<div class="row">
  <div class="col-xs-2">
    <input type="text" class="form-control" placeholder=".col-xs-2">
  </div>
  <div class="col-xs-3">
    <input type="text" class="form-control" placeholder=".col-xs-3">
  </div>
  <div class="col-xs-4">
    <input type="text" class="form-control" placeholder=".col-xs-4">
  </div>
</div>

Help text

Block level help text for form controls.

<span class="help-block">A block of help text that breaks onto a new line and may extend beyond one line.</span>

Options

Use any of the available button classes to quickly create a styled button.

<!-- Standard button -->
<button type="button" class="btn btn-default">Default</button>

<!-- Provides extra visual weight and identifies the primary action in a set of buttons -->
<button type="button" class="btn btn-primary">Primary</button>

<!-- Indicates a successful or positive action -->
<button type="button" class="btn btn-success">Success</button>

<!-- Contextual button for informational alert messages -->
<button type="button" class="btn btn-info">Info</button>

<!-- Indicates caution should be taken with this action -->
<button type="button" class="btn btn-warning">Warning</button>

<!-- Indicates a dangerous or potentially negative action -->
<button type="button" class="btn btn-danger">Danger</button>

<!-- Deemphasize a button by making it look like a link while maintaining button behavior -->
<button type="button" class="btn btn-link">Link</button>

Sizes

Fancy larger or smaller buttons? Add .btn-lg, .btn-sm, or .btn-xs for additional sizes.

<p>
  <button type="button" class="btn btn-primary btn-lg">Large button</button>
  <button type="button" class="btn btn-default btn-lg">Large button</button>
</p>
<p>
  <button type="button" class="btn btn-primary">Default button</button>
  <button type="button" class="btn btn-default">Default button</button>
</p>
<p>
  <button type="button" class="btn btn-primary btn-sm">Small button</button>
  <button type="button" class="btn btn-default btn-sm">Small button</button>
</p>
<p>
  <button type="button" class="btn btn-primary btn-xs">Extra small button</button>
  <button type="button" class="btn btn-default btn-xs">Extra small button</button>
</p>

Create block level buttons—those that span the full width of a parent— by adding .btn-block.

<button type="button" class="btn btn-primary btn-lg btn-block">Block level button</button>
<button type="button" class="btn btn-default btn-lg btn-block">Block level button</button>

Active state

Buttons will appear pressed (with a darker background, darker border, and inset shadow) when active. For <button> elements, this is done via :active. For <a> elements, it's done with .active. However, you may use .active on <button>s should you need to replicate the active state programmatically.

Button element

No need to add :active as it's a pseudo-class, but if you need to force the same appearance, go ahead and add .active.

<button type="button" class="btn btn-primary btn-lg active">Primary button</button>
<button type="button" class="btn btn-default btn-lg active">Button</button>

Anchor element

Add the .active class to <a> buttons.

Primary link Link

<a href="#" class="btn btn-primary btn-lg active" role="button">Primary link</a>
<a href="#" class="btn btn-default btn-lg active" role="button">Link</a>

Disabled state

Make buttons look unclickable by fading them back 50%.

Button element

Add the disabled attribute to <button> buttons.

<button type="button" class="btn btn-lg btn-primary" disabled="disabled">Primary button</button>
<button type="button" class="btn btn-default btn-lg" disabled="disabled">Button</button>

Cross-browser compatibility

If you add the disabled attribute to a <button>, Internet Explorer 9 and below will render text gray with a nasty text-shadow that we cannot fix.

Anchor element

Add the .disabled class to <a> buttons.

Primary link Link

<a href="#" class="btn btn-primary btn-lg disabled" role="button">Primary link</a>
<a href="#" class="btn btn-default btn-lg disabled" role="button">Link</a>

We use .disabled as a utility class here, similar to the common .active class, so no prefix is required.

Link functionality caveat

This class uses pointer-events: none to try to disable the link functionality of <a>s, but that CSS property is not yet standardized and isn't fully supported in Opera 18 and below, or in Internet Explorer 11. So to be safe, use custom JavaScript to disable such links.

Context-specific usage

While button classes can be used on <a> and <button> elements, only <button> elements are supported within our nav and navbar components.

Button tags

Use the button classes on an <a>, <button>, or <input> element.

<a class="btn btn-default" href="#" role="button">Link</a>
<button class="btn btn-default" type="submit">Button</button>
<input class="btn btn-default" type="button" value="Input">
<input class="btn btn-default" type="submit" value="Submit">

Cross-browser rendering

As a best practice, we highly recommend using the <button> element whenever possible to ensure matching cross-browser rendering.

Among other things, there's a bug in Firefox <30 that prevents us from setting the line-height of <input>-based buttons, causing them to not exactly match the height of other buttons on Firefox.

Responsive images

Images in Bootstrap 3 can be made responsive-friendly via the addition of the .img-responsive class. This applies max-width: 100%; and height: auto; to the image so that it scales nicely to the parent element.

<img src="..." class="img-responsive" alt="Responsive image">

Image shapes

Add classes to an <img> element to easily style images in any project.

Cross-browser compatibility

Keep in mind that Internet Explorer 8 lacks support for rounded corners.

A generic square placeholder image with rounded corners

A generic square placeholder image where only the portion within the circle circumscribed about said square is visible

A generic square placeholder image with a white border around it, making it resemble a photograph taken with an old instant camera

<img src="..." alt="..." class="img-rounded">
<img src="..." alt="..." class="img-circle">
<img src="..." alt="..." class="img-thumbnail">

Contextual colors

Convey meaning through color with a handful of emphasis utility classes. These may also be applied to links and will darken on hover just like our default link styles.

Fusce dapibus, tellus ac cursus commodo, tortor mauris nibh.

Nullam id dolor id nibh ultricies vehicula ut id elit.

Duis mollis, est non commodo luctus, nisi erat porttitor ligula.

Maecenas sed diam eget risus varius blandit sit amet non magna.

Etiam porta sem malesuada magna mollis euismod.

Donec ullamcorper nulla non metus auctor fringilla.

<p class="text-muted">...</p>
<p class="text-primary">...</p>
<p class="text-success">...</p>
<p class="text-info">...</p>
<p class="text-warning">...</p>
<p class="text-danger">...</p>

Dealing with specificity

Sometimes emphasis classes cannot be applied due to the specificity of another selector. In most cases, a sufficient workaround is to wrap your text in a <span> with the class.

Contextual backgrounds

Similar to the contextual text color classes, easily set the background of an element to any contextual class. Anchor components will darken on hover, just like the text classes.

Nullam id dolor id nibh ultricies vehicula ut id elit.

Duis mollis, est non commodo luctus, nisi erat porttitor ligula.

Maecenas sed diam eget risus varius blandit sit amet non magna.

Etiam porta sem malesuada magna mollis euismod.

Donec ullamcorper nulla non metus auctor fringilla.

<p class="bg-primary">...</p>
<p class="bg-success">...</p>
<p class="bg-info">...</p>
<p class="bg-warning">...</p>
<p class="bg-danger">...</p>

Dealing with specificity

Sometimes contextual background classes cannot be applied due to the specificity of another selector. In some cases, a sufficient workaround is to wrap your element's content in a <div> with the class.

Close icon

Use the generic close icon for dismissing content like modals and alerts.

<button type="button" class="close"><span aria-hidden="true">&times;</span><span class="sr-only">Close</span></button>

Carets

Use carets to indicate dropdown functionality and direction. Note that the default caret will reverse automatically in dropup menus.

<span class="caret"></span>

Quick floats

Float an element to the left or right with a class. !important is included to avoid specificity issues. Classes can also be used as mixins.

<div class="pull-left">...</div>
<div class="pull-right">...</div>

// Classes
.pull-left {
  float: left !important;
}
.pull-right {
  float: right !important;
}

// Usage as mixins
.element {
  .pull-left();
}
.another-element {
  .pull-right();
}

Not for use in navbars

To align components in navbars with utility classes, use .navbar-left or .navbar-right instead. See the navbar docs for details.

Center content blocks

Set an element to display: block and center via margin. Available as a mixin and class.

<div class="center-block">...</div>

// Classes
.center-block {
  display: block;
  margin-left: auto;
  margin-right: auto;
}

// Usage as mixins
.element {
  .center-block();
}

Clearfix

Easily clear floats by adding .clearfix to the parent element. Utilizes the micro clearfix as popularized by Nicolas Gallagher. Can also be used as a mixin.

<!-- Usage as a class -->
<div class="clearfix">...</div>

// Mixin itself
.clearfix() {
  &:before,
  &:after {
    content: " ";
    display: table;
  }
  &:after {
    clear: both;
  }
}

// Usage as a Mixin
.element {
  .clearfix();
}

Showing and hiding content

Force an element to be shown or hidden (including for screen readers) with the use of .show and .hidden classes. These classes use !important to avoid specificity conflicts, just like the quick floats. They are only available for block level toggling. They can also be used as mixins.

.hide is available, but it does not always affect screen readers and is deprecated as of v3.0.1. Use .hidden or .sr-only instead.

Furthermore, .invisible can be used to toggle only the visibility of an element, meaning its display is not modified and the element can still affect the flow of the document.

<div class="show">...</div>
<div class="hidden">...</div>

// Classes
.show {
  display: block !important;
}
.hidden {
  display: none !important;
  visibility: hidden !important;
}
.invisible {
  visibility: hidden;
}

// Usage as mixins
.element {
  .show();
}
.another-element {
  .hidden();
}

Screen reader and keyboard navigation content

Hide an element to all devices except screen readers with .sr-only. Combine .sr-only with .sr-only-focusable to show the element again when it's focused (e.g. by a keyboard-only user). Necessary for following accessibility best practices. Can also be used as mixins.

<a class="sr-only sr-only-focusable" href="#content">Skip to main content</a>

// Usage as a Mixin
.skip-navigation {
  .sr-only();
  .sr-only-focusable();
}

Image replacement

Utilize the .text-hide class or mixin to help replace an element's text content with a background image.

<h1 class="text-hide">Custom heading</h1>

// Usage as a Mixin
.heading {
  .text-hide();
}

For faster mobile-friendly development, use these utility classes for showing and hiding content by device via media query. Also included are utility classes for toggling content when printed.

Try to use these on a limited basis and avoid creating entirely different versions of the same site. Instead, use them to complement each device's presentation.

Available classes

Use a single or combination of the available classes for toggling content across viewport breakpoints.

	Extra small devices Phones (<768px)	Small devices Tablets (≥768px)	Medium devices Desktops (≥992px)	Large devices Desktops (≥1200px)
`.visible-xs-*`	Visible	Hidden	Hidden	Hidden
`.visible-sm-*`	Hidden	Visible	Hidden	Hidden
`.visible-md-*`	Hidden	Hidden	Visible	Hidden
`.visible-lg-*`	Hidden	Hidden	Hidden	Visible
`.hidden-xs`	Hidden	Visible	Visible	Visible
`.hidden-sm`	Visible	Hidden	Visible	Visible
`.hidden-md`	Visible	Visible	Hidden	Visible
`.hidden-lg`	Visible	Visible	Visible	Hidden

As of v3.2.0, the .visible-*-* classes for each breakpoint come in three variations, one for each CSS display property value listed below.

Group of classes	CSS `display`
`.visible-*-block`	`display: block;`
`.visible-*-inline`	`display: inline;`
`.visible-*-inline-block`	`display: inline-block;`

So, for extra small (xs) screens for example, the available .visible-*-* classes are: .visible-xs-block, .visible-xs-inline, and .visible-xs-inline-block.

The classes .visible-xs, .visible-sm, .visible-md, and .visible-lg also exist, but are deprecated as of v3.2.0. They are approximately equivalent to .visible-*-block, except with additional special cases for toggling <table>-related elements.

Print classes

Similar to the regular responsive classes, use these for toggling content for print.

Classes	Browser	Print
`.visible-print-block` `.visible-print-inline` `.visible-print-inline-block`	Hidden	Visible
`.hidden-print`	Visible	Hidden

The class .visible-print also exists but is deprecated as of v3.2.0. It is approximately equivalent to .visible-print-block, except with additional special cases for <table>-related elements.

Test cases

Resize your browser or load on different devices to test the responsive utility classes.

Visible on...

Green checkmarks indicate the element is visible in your current viewport.

Extra small ✔ Visible on x-small

Small ✔ Visible on small

Medium ✔ Visible on medium

Large ✔ Visible on large

Extra small and small ✔ Visible on x-small and small

Medium and large ✔ Visible on medium and large

Extra small and medium ✔ Visible on x-small and medium

Small and large ✔ Visible on small and large

Extra small and large ✔ Visible on x-small and large

Small and medium ✔ Visible on small and medium

Hidden on...

Here, green checkmarks also indicate the element is hidden in your current viewport.

Extra small ✔ Hidden on x-small

Small ✔ Hidden on small

Medium ✔ Hidden on medium

Large ✔ Hidden on large

Extra small and small ✔ Hidden on x-small and small

Medium and large ✔ Hidden on medium and large

Extra small and medium ✔ Hidden on x-small and medium

Small and large ✔ Hidden on small and large

Extra small and large ✔ Hidden on x-small and large

Small and medium ✔ Hidden on small and medium

Bootstrap's CSS is built on Less, a preprocessor with additional functionality like variables, mixins, and functions for compiling CSS. Those looking to use the source Less files instead of our compiled CSS files can make use of the numerous variables and mixins we use throughout the framework.

Grid variables and mixins are covered within the Grid system section.

Compiling Bootstrap

Bootstrap can be used in at least two ways: with the compiled CSS or with the source Less files. To compile the Less files, visit the README for how to setup your development environment to run the necessary commands.

Third party compilation tools may work with Bootstrap, but they are not supported by our core team.

Variables

Variables are used throughout the entire project as a way to centralize and share commonly used values like colors, spacing, or font stacks. For a complete breakdown, please see the Customizer.

Colors

Easily make use of two color schemes: grayscale and semantic. Grayscale colors provide quick access to commonly used shades of black while semantic include various colors assigned to meaningful contextual values.

@gray-darker:  lighten(#000, 13.5%); // #222
@gray-dark:    lighten(#000, 20%);   // #333
@gray:         lighten(#000, 33.5%); // #555
@gray-light:   lighten(#000, 46.7%); // #777
@gray-lighter: lighten(#000, 93.5%); // #eee

@brand-primary: #428bca;
@brand-success: #5cb85c;
@brand-info:    #5bc0de;
@brand-warning: #f0ad4e;
@brand-danger:  #d9534f;

Use any of these color variables as they are or reassign them to more meaningful variables for your project.

// Use as-is
.masthead {
  background-color: @brand-primary;
}

// Reassigned variables in Less
@alert-message-background: @brand-info;
.alert {
  background-color: @alert-message-background;
}

Scaffolding

A handful of variables for quickly customizing key elements of your site's skeleton.

// Scaffolding
@body-bg:    #fff;
@text-color: @black-50;

Links

Easily style your links with the right color with only one value.

// Variables
@link-color:       @brand-primary;
@link-hover-color: darken(@link-color, 15%);

// Usage
a {
  color: @link-color;
  text-decoration: none;

  &:hover {
    color: @link-hover-color;
    text-decoration: underline;
  }
}

Note that the @link-hover-color uses a function, another awesome tool from Less, to automagically create the right hover color. You can use darken, lighten, saturate, and desaturate.

Typography

Easily set your type face, text size, leading, and more with a few quick variables. Bootstrap makes use of these as well to provide easy typographic mixins.

@font-family-sans-serif:  "Helvetica Neue", Helvetica, Arial, sans-serif;
@font-family-serif:       Georgia, "Times New Roman", Times, serif;
@font-family-monospace:   Menlo, Monaco, Consolas, "Courier New", monospace;
@font-family-base:        @font-family-sans-serif;

@font-size-base:          14px;
@font-size-large:         ceil((@font-size-base * 1.25)); // ~18px
@font-size-small:         ceil((@font-size-base * 0.85)); // ~12px

@font-size-h1:            floor((@font-size-base * 2.6)); // ~36px
@font-size-h2:            floor((@font-size-base * 2.15)); // ~30px
@font-size-h3:            ceil((@font-size-base * 1.7)); // ~24px
@font-size-h4:            ceil((@font-size-base * 1.25)); // ~18px
@font-size-h5:            @font-size-base;
@font-size-h6:            ceil((@font-size-base * 0.85)); // ~12px

@line-height-base:        1.428571429; // 20/14
@line-height-computed:    floor((@font-size-base * @line-height-base)); // ~20px

@headings-font-family:    inherit;
@headings-font-weight:    500;
@headings-line-height:    1.1;
@headings-color:          inherit;

Icons

Two quick variables for customizing the location and filename of your icons.

@icon-font-path:          "../fonts/";
@icon-font-name:          "glyphicons-halflings-regular";

Components

Components throughout Bootstrap make use of some default variables for setting common values. Here are the most commonly used.

@padding-base-vertical:          6px;
@padding-base-horizontal:        12px;

@padding-large-vertical:         10px;
@padding-large-horizontal:       16px;

@padding-small-vertical:         5px;
@padding-small-horizontal:       10px;

@padding-xs-vertical:            1px;
@padding-xs-horizontal:          5px;

@line-height-large:              1.33;
@line-height-small:              1.5;

@border-radius-base:             4px;
@border-radius-large:            6px;
@border-radius-small:            3px;

@component-active-color:         #fff;
@component-active-bg:            @brand-primary;

@caret-width-base:               4px;
@caret-width-large:              5px;

Vendor mixins

Vendor mixins are mixins to help support multiple browsers by including all relevant vendor prefixes in your compiled CSS.

Box-sizing

Reset your components' box model with a single mixin. For context, see this helpful article from Mozilla.

The mixin is deprecated as of v3.2.0, with the introduction of autoprefixer. To preserve backwards-compatibility, Bootstrap will continue to use the mixin internally until Bootstrap v4.

.box-sizing(@box-model) {
  -webkit-box-sizing: @box-model; // Safari <= 5
     -moz-box-sizing: @box-model; // Firefox <= 19
          box-sizing: @box-model;
}

Rounded corners

Today all modern browsers support the non-prefixed border-radius property. As such, there is no .border-radius() mixin, but Bootstrap does include shortcuts for quickly rounding two corners on a particular side of an object.

.border-top-radius(@radius) {
  border-top-right-radius: @radius;
   border-top-left-radius: @radius;
}
.border-right-radius(@radius) {
  border-bottom-right-radius: @radius;
     border-top-right-radius: @radius;
}
.border-bottom-radius(@radius) {
  border-bottom-right-radius: @radius;
   border-bottom-left-radius: @radius;
}
.border-left-radius(@radius) {
  border-bottom-left-radius: @radius;
     border-top-left-radius: @radius;
}

Box (Drop) shadows

If your target audience is using the latest and greatest browsers and devices, be sure to just use the box-shadow property on its own. If you need support for older Android (pre-v4) and iOS devices (pre-iOS 5), use the deprecated mixin to pick up the required -webkit prefix.

The mixin is deprecated as of v3.1.0, since Bootstrap doesn't officially support the outdated platforms that don't support the standard property. To preserve backwards-compatibility, Bootstrap will continue to use the mixin internally until Bootstrap v4.

Be sure to use rgba() colors in your box shadows so they blend as seamlessly as possible with backgrounds.

.box-shadow(@shadow: 0 1px 3px rgba(0,0,0,.25)) {
  -webkit-box-shadow: @shadow; // iOS <4.3 & Android <4.1
          box-shadow: @shadow;
}

Transitions

Multiple mixins for flexibility. Set all transition information with one, or specify a separate delay and duration as needed.

The mixins are deprecated as of v3.2.0, with the introduction of autoprefixer. To preserve backwards-compatibility, Bootstrap will continue to use the mixins internally until Bootstrap v4.

.transition(@transition) {
  -webkit-transition: @transition;
          transition: @transition;
}
.transition-property(@transition-property) {
  -webkit-transition-property: @transition-property;
          transition-property: @transition-property;
}
.transition-delay(@transition-delay) {
  -webkit-transition-delay: @transition-delay;
          transition-delay: @transition-delay;
}
.transition-duration(@transition-duration) {
  -webkit-transition-duration: @transition-duration;
          transition-duration: @transition-duration;
}
.transition-timing-function(@timing-function) {
  -webkit-transition-timing-function: @timing-function;
          transition-timing-function: @timing-function;
}
.transition-transform(@transition) {
  -webkit-transition: -webkit-transform @transition;
     -moz-transition: -moz-transform @transition;
       -o-transition: -o-transform @transition;
          transition: transform @transition;
}

Transformations

Rotate, scale, translate (move), or skew any object.

The mixins are deprecated as of v3.2.0, with the introduction of autoprefixer. To preserve backwards-compatibility, Bootstrap will continue to use the mixins internally until Bootstrap v4.

.rotate(@degrees) {
  -webkit-transform: rotate(@degrees);
      -ms-transform: rotate(@degrees); // IE9 only
          transform: rotate(@degrees);
}
.scale(@ratio; @ratio-y...) {
  -webkit-transform: scale(@ratio, @ratio-y);
      -ms-transform: scale(@ratio, @ratio-y); // IE9 only
          transform: scale(@ratio, @ratio-y);
}
.translate(@x; @y) {
  -webkit-transform: translate(@x, @y);
      -ms-transform: translate(@x, @y); // IE9 only
          transform: translate(@x, @y);
}
.skew(@x; @y) {
  -webkit-transform: skew(@x, @y);
      -ms-transform: skewX(@x) skewY(@y); // See https://github.com/twbs/bootstrap/issues/4885; IE9+
          transform: skew(@x, @y);
}
.translate3d(@x; @y; @z) {
  -webkit-transform: translate3d(@x, @y, @z);
          transform: translate3d(@x, @y, @z);
}

.rotateX(@degrees) {
  -webkit-transform: rotateX(@degrees);
      -ms-transform: rotateX(@degrees); // IE9 only
          transform: rotateX(@degrees);
}
.rotateY(@degrees) {
  -webkit-transform: rotateY(@degrees);
      -ms-transform: rotateY(@degrees); // IE9 only
          transform: rotateY(@degrees);
}
.perspective(@perspective) {
  -webkit-perspective: @perspective;
     -moz-perspective: @perspective;
          perspective: @perspective;
}
.perspective-origin(@perspective) {
  -webkit-perspective-origin: @perspective;
     -moz-perspective-origin: @perspective;
          perspective-origin: @perspective;
}
.transform-origin(@origin) {
  -webkit-transform-origin: @origin;
     -moz-transform-origin: @origin;
      -ms-transform-origin: @origin; // IE9 only
          transform-origin: @origin;
}

Animations

A single mixin for using all of CSS3's animation properties in one declaration and other mixins for individual properties.

The mixins are deprecated as of v3.2.0, with the introduction of autoprefixer. To preserve backwards-compatibility, Bootstrap will continue to use the mixins internally until Bootstrap v4.

.animation(@animation) {
  -webkit-animation: @animation;
          animation: @animation;
}
.animation-name(@name) {
  -webkit-animation-name: @name;
          animation-name: @name;
}
.animation-duration(@duration) {
  -webkit-animation-duration: @duration;
          animation-duration: @duration;
}
.animation-timing-function(@timing-function) {
  -webkit-animation-timing-function: @timing-function;
          animation-timing-function: @timing-function;
}
.animation-delay(@delay) {
  -webkit-animation-delay: @delay;
          animation-delay: @delay;
}
.animation-iteration-count(@iteration-count) {
  -webkit-animation-iteration-count: @iteration-count;
          animation-iteration-count: @iteration-count;
}
.animation-direction(@direction) {
  -webkit-animation-direction: @direction;
          animation-direction: @direction;
}

Opacity

Set the opacity for all browsers and provide a filter fallback for IE8.

.opacity(@opacity) {
  opacity: @opacity;
  // IE8 filter
  @opacity-ie: (@opacity * 100);
  filter: ~"alpha(opacity=@{opacity-ie})";
}

Placeholder text

Provide context for form controls within each field.

.placeholder(@color: @input-color-placeholder) {
  &::-moz-placeholder           { color: @color; } // Firefox
  &:-ms-input-placeholder       { color: @color; } // Internet Explorer 10+
  &::-webkit-input-placeholder  { color: @color; } // Safari and Chrome
}

Columns

Generate columns via CSS within a single element.

.content-columns(@width; @count; @gap) {
  -webkit-column-width: @width;
     -moz-column-width: @width;
          column-width: @width;
  -webkit-column-count: @count;
     -moz-column-count: @count;
          column-count: @count;
  -webkit-column-gap: @gap;
     -moz-column-gap: @gap;
          column-gap: @gap;
}

Gradients

Easily turn any two colors into a background gradient. Get more advanced and set a direction, use three colors, or use a radial gradient. With a single mixin you get all the prefixed syntaxes you'll need.

#gradient > .vertical(#333; #000);
#gradient > .horizontal(#333; #000);
#gradient > .radial(#333; #000);

You can also specify the angle of a standard two-color, linear gradient:

#gradient > .directional(#333; #000; 45deg);

If you need a barber-stripe style gradient, that's easy, too. Just specify a single color and we'll overlay a translucent white stripe.

#gradient > .striped(#333; 45deg);

Up the ante and use three colors instead. Set the first color, the second color, the second color's color stop (a percentage value like 25%), and the third color with these mixins:

#gradient > .vertical-three-colors(#777; #333; 25%; #000);
#gradient > .horizontal-three-colors(#777; #333; 25%; #000);

Heads up! Should you ever need to remove a gradient, be sure to remove any IE-specific filter you may have added. You can do that by using the .reset-filter() mixin alongside background-image: none;.

Utility mixins

Utility mixins are mixins that combine otherwise unrelated CSS properties to achieve a specific goal or task.

Clearfix

Forget adding class="clearfix" to any element and instead add the .clearfix() mixin where appropriate. Uses the micro clearfix from Nicolas Gallager.

// Mixin
.clearfix() {
  &:before,
  &:after {
    content: " ";
    display: table;
  }
  &:after {
    clear: both;
  }
}

// Usage
.container {
  .clearfix();
}

Horizontal centering

Quickly center any element within its parent. Requires width or max-width to be set.

// Mixin
.center-block() {
  display: block;
  margin-left: auto;
  margin-right: auto;
}

// Usage
.container {
  width: 940px;
  .center-block();
}

Sizing helpers

Specify the dimensions of an object more easily.

// Mixins
.size(@width; @height) {
  width: @width;
  height: @height;
}
.square(@size) {
  .size(@size; @size);
}

// Usage
.image { .size(400px; 300px); }
.avatar { .square(48px); }

Resizable textareas

Easily configure the resize options for any textarea, or any other element. Defaults to normal browser behavior (both).

.resizable(@direction: both) {
  // Options: horizontal, vertical, both
  resize: @direction;
  // Safari fix
  overflow: auto;
}

Truncating text

Easily truncate text with an ellipsis with a single mixin. Requires element to be block or inline-block level.

// Mixin
.text-overflow() {
  overflow: hidden;
  text-overflow: ellipsis;
  white-space: nowrap;
}

// Usage
.branch-name {
  display: inline-block;
  max-width: 200px;
  .text-overflow();
}

Retina images

Specify two image paths and the @1x image dimensions, and Bootstrap will provide an @2x media query. If you have many images to serve, consider writing your retina image CSS manually in a single media query.

.img-retina(@file-1x; @file-2x; @width-1x; @height-1x) {
  background-image: url("@{file-1x}");

  @media
  only screen and (-webkit-min-device-pixel-ratio: 2),
  only screen and (   min--moz-device-pixel-ratio: 2),
  only screen and (     -o-min-device-pixel-ratio: 2/1),
  only screen and (        min-device-pixel-ratio: 2),
  only screen and (                min-resolution: 192dpi),
  only screen and (                min-resolution: 2dppx) {
    background-image: url("@{file-2x}");
    background-size: @width-1x @height-1x;
  }
}

// Usage
.jumbotron {
  .img-retina("/img/bg-1x.png", "/img/bg-2x.png", 100px, 100px);
}

While Bootstrap is built on Less, it also has an official Sass port. We maintain it in a separate GitHub repository and handle updates with a conversion script.

What's included

Since the Sass port has a separate repo and serves a slightly different audience, the contents of the project differ greatly from the main Bootstrap project. This ensures the Sass port is as compatible with as many Sass-based systems as possible.

Path	Description
`lib/`	Ruby gem code (Sass configuration, Rails and Compass integrations)
`tasks/`	Converter scripts (turning upstream Less to Sass)
`test/`	Compilation tests
`templates/`	Compass package manifest
`vendor/assets/`	Sass, JavaScript, and font files
`Rakefile`	Internal tasks, such as rake and convert

Visit the Sass port's GitHub repository to see these files in action.

Installation

For information on how to install and use Bootstrap for Sass, consult the GitHub repository readme. It's the most up to date source and includes information for use with Rails, Compass, and standard Sass projects.

Bootstrap for Sass

全局CSS样式

概览

HTML5 doctype-HTML页面文档头

css 重置(TODO：base.css有待分离)

排版

页面背景，字体与链接

标题

h1. TWUI heading

h2. TWUI heading

h3. TWUI heading

h4. TWUI heading

h5. TWUI heading

h6. TWUI heading

文本

带链接文本

页面主体

使用 Less 工具构建

对齐

列表

基本无序列表

Code

Inline

User input

Basic block

Variables

Sample output

Tables

Basic example

Striped rows

Cross-browser compatibility

Bordered table

Hover rows

Condensed table

Contextual classes

Responsive tables

Firefox and fieldsets

Forms

Basic example

Don't mix form groups with input groups

Inline form

Requires custom widths

Always add labels

Horizontal form

Supported controls

Inputs

Type declaration required

Input groups

Textarea

Checkboxes and radios

Default (stacked)

Inline checkboxes and radios

Selects

Static control

Input focus

Demo :focus state

Disabled inputs

Disabled fieldsets

Caveat about link functionality of <a>

Cross-browser compatibility

Readonly inputs

Validation states

With optional icons

Icons, labels, and input groups

Optional icons in horizontal and inline forms

Optional icons with hidden .sr-only labels

Control sizing

Height sizing

Horizontal form group sizes

Column sizing

Help text

Buttons

Options

Sizes

Active state

Button element

Anchor element

Disabled state

Button element

Cross-browser compatibility

Anchor element

Demo `:focus` state

Caveat about link functionality of `<a>`

Optional icons with hidden `.sr-only` labels