CSS/CSS3 7 常见“坑”

1 移动端 1像素边框

产生原因：retina屏 厂商将多个像素点压缩为一个逻辑像素中 达到高清效果。

物理像素 移动设备出厂时，不同设备自带的不同像素，也称硬件像素；

逻辑像素 即css中记录的像素。

当我们使用1px时会产生 2px 3px的宽度。

解决方案1 媒体查询

.border { border: 1px solid #999 }
@media screen and (-webkit-min-device-pixel-ratio: 2) {
    .border { border: 0.5px solid #999 }
}
@media screen and (-webkit-min-device-pixel-ratio: 3) {
.border { border: 0.333333px solid #999 }
}

缺点 对设备有要求，小数像素目前兼容性较差。

解决方案2 transform:scale(0,5)

.div::after {
    content: '';
    width: 200%;
    height: 200%;
    position: absolute;
    top: 0;
    left: 0;
    border: 1px solid #bfbfbf;
    border-radius: 4px;
    -webkit-transform: scale(0.5,0.5);
    transform: scale(0.5,0.5);
    -webkit-transform-origin: top left;
}

可以通过媒体查询来设置缩放比例

/* 2倍屏 */
@media only screen and (-webkit-min-device-pixel-ratio: 2.0) {
    .border-bottom::after {
        -webkit-transform: scaleY(0.5);
        transform: scaleY(0.5);
    }
}

/* 3倍屏 */
@media only screen and (-webkit-min-device-pixel-ratio: 3.0) {
    .border-bottom::after {
        -webkit-transform: scaleY(0.33);
        transform: scaleY(0.33);
    }
}

引入 border.css

@charset "utf-8";

.border,
.border-top,
.border-right,
.border-bottom,
.border-left,
.border-topbottom,
.border-rightleft,
.border-topleft,
.border-rightbottom,
.border-topright,
.border-bottomleft {
  position: relative;
}

.border::before,
.border-top::before,
.border-right::before,
.border-bottom::before,
.border-left::before,
.border-topbottom::before,
.border-topbottom::after,
.border-rightleft::before,
.border-rightleft::after,
.border-topleft::before,
.border-topleft::after,
.border-rightbottom::before,
.border-rightbottom::after,
.border-topright::before,
.border-topright::after,
.border-bottomleft::before,
.border-bottomleft::after {
  content: "\0020";
  overflow: hidden;
  position: absolute;
}

/* border
 * 因，边框是由伪元素区域遮盖在父级
 * 故，子级若有交互，需要对子级设置
 * 定位 及 z轴
 */
.border::before {
  box-sizing: border-box;
  top: 0;
  left: 0;
  height: 100%;
  width: 100%;
  border: 1px solid #eaeaea;
  transform-origin: 0 0;
}

.border-top::before,
.border-bottom::before,
.border-topbottom::before,
.border-topbottom::after,
.border-topleft::before,
.border-rightbottom::after,
.border-topright::before,
.border-bottomleft::before {
  left: 0;
  width: 100%;
  height: 1px;
}

.border-right::before,
.border-left::before,
.border-rightleft::before,
.border-rightleft::after,
.border-topleft::after,
.border-rightbottom::before,
.border-topright::after,
.border-bottomleft::after {
  top: 0;
  width: 1px;
  height: 100%;
}

.border-top::before,
.border-topbottom::before,
.border-topleft::before,
.border-topright::before {
  border-top: 1px solid #eaeaea;
  transform-origin: 0 0;
}

.border-right::before,
.border-rightbottom::before,
.border-rightleft::before,
.border-topright::after {
  border-right: 1px solid #eaeaea;
  transform-origin: 100% 0;
}

.border-bottom::before,
.border-topbottom::after,
.border-rightbottom::after,
.border-bottomleft::before {
  border-bottom: 1px solid #eaeaea;
  transform-origin: 0 100%;
}

.border-left::before,
.border-topleft::after,
.border-rightleft::after,
.border-bottomleft::after {
  border-left: 1px solid #eaeaea;
  transform-origin: 0 0;
}

.border-top::before,
.border-topbottom::before,
.border-topleft::before,
.border-topright::before {
  top: 0;
}

.border-right::before,
.border-rightleft::after,
.border-rightbottom::before,
.border-topright::after {
  right: 0;
}

.border-bottom::before,
.border-topbottom::after,
.border-rightbottom::after,
.border-bottomleft::after {
  bottom: 0;
}

.border-left::before,
.border-rightleft::before,
.border-topleft::after,
.border-bottomleft::before {
  left: 0;
}

@media (max--moz-device-pixel-ratio: 1.49),
(-webkit-max-device-pixel-ratio: 1.49),
(max-device-pixel-ratio: 1.49),
(max-resolution: 143dpi),
(max-resolution: 1.49dppx) {
  /* 默认值，无需重置 */
}

@media (min--moz-device-pixel-ratio: 1.5) and (max--moz-device-pixel-ratio: 2.49),
(-webkit-min-device-pixel-ratio: 1.5) and (-webkit-max-device-pixel-ratio: 2.49),
(min-device-pixel-ratio: 1.5) and (max-device-pixel-ratio: 2.49),
(min-resolution: 144dpi) and (max-resolution: 239dpi),
(min-resolution: 1.5dppx) and (max-resolution: 2.49dppx) {
  .border::before {
    width: 200%;
    height: 200%;
    transform: scale(.5);
  }

  .border-top::before,
  .border-bottom::before,
  .border-topbottom::before,
  .border-topbottom::after,
  .border-topleft::before,
  .border-rightbottom::after,
  .border-topright::before,
  .border-bottomleft::before {
    transform: scaleY(.5);
  }

  .border-right::before,
  .border-left::before,
  .border-rightleft::before,
  .border-rightleft::after,
  .border-topleft::after,
  .border-rightbottom::before,
  .border-topright::after,
  .border-bottomleft::after {
    transform: scaleX(.5);
  }
}

@media (min--moz-device-pixel-ratio: 2.5),
(-webkit-min-device-pixel-ratio: 2.5),
(min-device-pixel-ratio: 2.5),
(min-resolution: 240dpi),
(min-resolution: 2.5dppx) {
  .border::before {
    width: 300%;
    height: 300%;
    transform: scale(.33333);
  }

  .border-top::before,
  .border-bottom::before,
  .border-topbottom::before,
  .border-topbottom::after,
  .border-topleft::before,
  .border-rightbottom::after,
  .border-topright::before,
  .border-bottomleft::before {
    transform: scaleY(.33333);
  }

  .border-right::before,
  .border-left::before,
  .border-rightleft::before,
  .border-rightleft::after,
  .border-topleft::after,
  .border-rightbottom::before,
  .border-topright::after,
  .border-bottomleft::after {
    transform: scaleX(.33333);
  }
}

2 文字超出省略号

单行

.box{
  white-space: nowrap;
  overflow: hidden;
  text-overflow: ellipsis;
}

多行

.box {
  display: -webkit-box;
  overflow: hidden;
  -webkit-line-clamp: 2;
  -webkit-box-orient: vertical;
}

3 清除浮动

1 额外标签法

在最后一个浮动的标签后添加元素 属性为 clear:both （不推荐）

2 overflow：hidden

父级添加overflow：hidden（不推荐）

3 after

给元素添加：after伪元素 设置属性

box:after{
    content: "";
    display: block;
    height: 0;
    clear:both;
    visibility: hidden;
}

4 after before

.box:after,.box:before{
    content: "";
    display: table;
}
.box:after{
    clear: both;
}
.box{
    *zoom: 1;
}