font
====

概述
--

`font` 属性可以用来作为 `font-style`, `font-variant`, `font-weight`, `font-size`, `line-height` 和 `font-family` 属性的简写，或将元素的字体设置为系统字体。

尝试一下
----

与任何简写属性一样，任何未指定的值都将设置为其对应的初始值（可能覆盖先前使用非简写属性设置的值）。虽然不能通过 font 直接设置，但是`font-stretch`，`font-size-adjust` 和 `font-kerning` 也会重置为初始值。

语法
--

可以将`font`属性指定为单个关键字，它将选择系统字体，或者作为字体相关的属性的简写。

如果将 `font` 指定为系统关键字，则它必须是以下之一：`caption`, `icon`, `menu`, `message-box`, `small-caption`, `status-bar`。

如果 `font` 字体相关的属性的简写：

* 必须包含以下值：
    + `<font-size>`
    + `<font-family>`
* 可以选择性包含以下值：
    + `<font-style>`
    + `<font-variant>`
    + `<font-weight>`
    + `<line-height>`
* `font-style`, `font-variant` 和 `font-weight` 必须在 `font-size` 之前
* 在 CSS 2.1 中 `font-variant` 只可以是 `normal` 和 `small-caps`
* `line-height` 必须跟在 `font-size` 后面，由 "/" 分隔，例如 "`16px/3`"
* `font-family` 必须最后指定
### 值

`<'font-style'>`

见 `font-style` 属性。

`<'font-variant'>`

见 `font-variant` 属性。

`<'font-weight'>`

见 `font-weight` 属性。

`<'font-size'>`

见 `font-size` 属性。

`<'line-height'>`

见 `line-height` 属性。

`<'font-family'>`

见 `font-family` 属性。

#### 系统字体

`caption`

用于标题控件（如按钮，下拉列表等）的系统字体。

`icon`

用于标签图标的系统字体。

`menu`

菜单中（如下拉菜单和菜单列表）使用的系统字体。

`message-box`

用于对话框的系统字体。

`small-caption`

用于小标题控件的系统字体。

`status-bar`

用于窗口状态栏的系统字体。

系统关键字前缀

浏览器经常会多实现几个带前缀的关键字；Gecko 实现了 `-moz-window`, `-moz-document`, `-moz-desktop`, `-moz-info`, `-moz-dialog`, `-moz-button`, `-moz-pull-down-menu`, `-moz-list`, 和 `-moz-field`.

### 形式语法
```

font =   
  [ [ <'font-style'> || <font-variant-css2> || <'font-weight'> || <font-stretch-css3> ]? <'font-size'> [ / <'line-height'> ]? <'font-family'> ]  |  
  <system-family-name>                                  
  
<font-variant-css2> =   
  normal      |  
  small-caps    
  
<font-stretch-css3> =   
  normal           |  
  ultra-condensed  |  
  extra-condensed  |  
  condensed        |  
  semi-condensed   |  
  semi-expanded    |  
  expanded         |  
  extra-expanded   |  
  ultra-expanded     
  
<system-family-name> =   
  caption        |  
  icon           |  
  menu           |  
  message-box    |  
  small-caption  |  
  status-bar       
  
```

示例
--

### 设置字体属性


```css
/\* Set the font size to 12px and the line height to 14px.
 Set the font family to sans-serif \*/
p {
  font: 12px/14px sans-serif;
}

/\* Set the font size to 80% of the parent element
 or default value (if no parent element present).
 Set the font family to sans-serif \*/
p {
  font: 80% sans-serif;
}

/\* Set the font weight to bold,
 the font-style to italic,
 the font size to large,
 and the font family to serif. \*/
p {
  font: bold italic large serif;
}

/\* Use the same font as the status bar of the window \*/
p {
  font: status-bar;
}
```

### 运行实例
```

<p>
  Change the radio buttons below to see the generated shorthand and its effect.
</p>
<form action="createShortHand()">
  <div class="cf">
    <div class="setPropCont">
      font-style<br />
      <input
 type="radio"
 id="font-style-none"
 name="font\_style"
 checked=""
 value=""
 onchange="setCss()" />
      <label for="font-style-none">none</label><br />
      <input
 type="radio"
 id="font-style-normal"
 name="font\_style"
 value="normal"
 onchange="setCss()" />
      <label for="font-style-normal">normal</label><br />
      <input
 type="radio"
 id="font-style-italic"
 name="font\_style"
 value="italic"
 onchange="setCss()" />
      <label for="font-style-italic">italic</label><br />
      <input
 type="radio"
 id="font-style-oblique"
 name="font\_style"
 value="oblique"
 onchange="setCss()" />
      <label for="font-style-oblique">oblique</label>
    </div>

    <div class="setPropCont">
      font-variant<br />
      <input
 type="radio"
 id="font-variant-none"
 name="font\_variant"
 checked=""
 value=" "
 onchange="setCss()" />
      <label for="font-variant-none">none</label><br />
      <input
 type="radio"
 id="font-variant-normal"
 name="font\_variant"
 value="normal"
 onchange="setCss()" />
      <label for="font-variant-normal">normal</label><br />
      <input
 type="radio"
 id="font-variant-small-caps"
 name="font\_variant"
 value="small-caps"
 onchange="setCss()" />
      <label for="font-variant-small-caps">small-caps</label>
    </div>

    <div class="setPropCont">
      font-weight<br />
      <input
 type="radio"
 id="font-weight-none"
 name="font\_weight"
 value=""
 onchange="setCss()" />
      <label for="font-weight-none">none</label><br />
      <input
 type="radio"
 id="font-weight-normal"
 checked=""
 name="font\_weight"
 value="400"
 onchange="setCss()" />
      <label for="font-weight-normal">normal</label><br />
      <input
 type="radio"
 id="font-weight-bold"
 name="font\_weight"
 value="700"
 onchange="setCss()" />
      <label for="font-weight-bold">bold</label>
    </div>

    <div class="setPropCont">
      font-size<br />
      <input
 type="radio"
 id="font-size-12px"
 name="font\_size"
 value="12px"
 onchange="setCss()" />
      <label for="font-size-12px">12px</label><br />
      <input
 type="radio"
 id="font-size-16px"
 name="font\_size"
 value="16px"
 checked=""
 onchange="setCss()" />
      <label for="font-size-16px">16px</label><br />
      <input
 type="radio"
 id="font-size-24px"
 name="font\_size"
 value="24px"
 onchange="setCss()" />
      <label for="font-size-24px">24px</label>
    </div>

    <div class="setPropCont">
      line-height<br />
      <input
 type="radio"
 id="line-height-none"
 name="line\_height"
 checked=""
 value=""
 onchange="setCss()" />
      <label for="line-height-none">none</label><br />
      <input
 type="radio"
 id="line-height-1.2"
 name="line\_height"
 value="/1.2"
 onchange="setCss()" />
      <label for="line-height-1.2">1.2</label><br />
      <input
 type="radio"
 id="line-height-3"
 name="line\_height"
 value="/3"
 onchange="setCss()" />
      <label for="line-height-3">3</label>
    </div>
    <br />

    <div class="setPropCont fontfamily">
      font-family<br />
      <input
 type="radio"
 id="font-family-courier"
 name="font\_family"
 checked=""
 value="courier"
 onchange="setCss(5,'courier')" />
      <label for="font-family-courier">courier</label><br />
      <input
 type="radio"
 id="font-family-serif"
 name="font\_family"
 value="serif"
 onchange="setCss()" />
      <label for="font-family-serif">serif</label><br />
      <input
 type="radio"
 id="font-family-sans-serif"
 name="font\_family"
 value="sans-serif"
 onchange="setCss()" />
      <label for="font-family-sans-serif">sans-serif</label><br />
      <input
 type="radio"
 id="font-family-arial"
 name="font\_family"
 value="arial"
 onchange="setCss()" />
      <label for="font-family-arial">Arial</label><br />
      <input
 type="radio"
 id="font-family-monospace"
 name="font\_family"
 value="monospace"
 onchange="setCss()" />
      <label for="font-family-monospace">monospace</label><br />
      <input
 type="radio"
 id="font-family-cursive"
 name="font\_family"
 value="cursive"
 onchange="setCss()" />
      <label for="font-family-cursive">cursive</label><br />
      <input
 type="radio"
 id="font-family-fantasy"
 name="font\_family"
 value="fantasy"
 onchange="setCss()" />
      <label for="font-family-fantasy">fantasy</label><br />
      <input
 type="radio"
 id="font-family-system-ui"
 name="font\_family"
 value="system-ui"
 onchange="setCss()" />
      <label for="font-family-system-ui">system-ui</label><br />
    </div>
  </div>

  <div class="cf propInputs">
    <div class="propInputCont tar">font :</div>
    <div class="propInputCont">
      <input type="text" class="curCss" id="input\_font\_style" /><br />
      font-style <br />
      optional
    </div>
    <div class="propInputCont">
      <input type="text" class="curCss" id="input\_font\_variant" /> <br />
      font-variant <br />
      optional
    </div>
    <div class="propInputCont">
      <input type="text" class="curCss" id="input\_font\_weight" /> <br />
      font-weight <br />
      optional
    </div>
    <div class="propInputCont">
      <input type="text" class="curCss mandatory" id="input\_font\_size" /> <br />
      font-size <br />
      mandatory
    </div>
    <div class="propInputCont">
      <input type="text" class="curCss" id="input\_line\_height" /> <br />
      line-height <br />
      optional
    </div>
    <div class="propInputCont">
      <input type="text" class="curCss mandatory" id="input\_font\_family" />
      <br />
      font-family <br />
      mandatory
    </div>
  </div>
</form>

<div class="fontShortHand">This is some sample text.</div>
<br /><br /><br /><br /><br /><br />
```


```
body,
input {
  font: 14px arial;
  overflow: hidden;
}

.propInputCont {
  float: left;
  text-align: center;
  margin-right: 5px;
  width: 80px;
}

.setPropCont {
  float: left;
  margin-right: 5px;
  width: 120px;
}

.propInputs,
.setPropCont {
  margin-bottom: 1em;
}

.curCss {
  border: none;
  border-bottom: 1px solid black;
  text-align: center;
  width: 80px;
}

.mandatory {
  border-bottom-color: red;
}

.cf::before,
.cf::after {
  content: " ";
  display: table;
}

.cf::after {
  clear: both;
}

.tar {
  width: 40px;
  text-align: right;
}
.fontfamily {
  display: inline-block;
}
```


```
const textAreas = document.getElementsByClassName("curCss");

function getProperties() {
  return (
    `${getCheckedValue("font\_style")} ` +
    `${getCheckedValue("font\_variant")} ` +
    `${getCheckedValue("font\_weight")} ` +
    `${getCheckedValue("font\_size")}` +
    `${getCheckedValue("line\_height")} ` +
    `${getCheckedValue("font\_family")}`
  );
}

function getCheckedValue(radioName) {
  const radios = document.forms[0].elements[radioName];
  for (let i = 0; i < radios.length; i++) {
    if (radios[i].checked) {
      const curElemName = `input\_${radioName}`;
      const curElem = document.getElementById(curElemName);
      curElem.value = radios[i].value;

      return radios[i].value;
    }
  }
}

function setCss() {
  getProperties();
  injectCss(shortText);
}

function injectCss(cssFragment) {
  const old = document.body.getElementsByTagName("style");
  if (old.length > 1) {
    old[1].parentElement.removeChild(old[1]);
  }
  css = document.createElement("style");
  css.textContent = `.fontShortHand{font: ${cssFragment}}`;
  document.body.appendChild(css);
}

setCss();
```

规范
--

| Specification |
| --- |
| CSS Fonts Module Level 4 # font-prop |

浏览器兼容性
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