以下是我已经远远尝试这个。
.container .form--container:before {
content: "";
position: absolute;
top: 0px;
left: 130px;
width: 28px;
height: 28px;
transform: translate(-1rem, -100%);
border-left: 1.5rem solid #979797;
border-right: 1.5rem solid #979797;
border-bottom: 1.5rem solid white;
}
这个问题与使用边界。你可以检查此链接How do CSS triangles work?,你会明白的边界是如何工作的,以及为什么你得到这个输出。
另一种解决方案是使用旋转和边界是这样的:
.box {
border: 1px solid;
margin: 50px;
height: 50px;
position:relative;
background: #f2f2f5;
}
.box:before {
content: "";
position: absolute;
width: 20px;
height: 20px;
border-top: 1px solid;
border-left: 1px solid;
top: -11px;
left: 13px;
background: #f2f2f5;
transform: rotate(45deg);
}
<div class="box">
</div>
而如果你想用箭头你的盒子是透明的,这里是另一个伎俩来实现它(如上述方案考虑纯色背景):
body {
margin:0;
background-image:linear-gradient(to right,yellow,pink);
}
.box {
border: 1px solid;
border-top:transparent; /*make border-top transparent*/
margin: 50px;
height: 50px;
position:relative;
/* Use gradient to mimic the border top with a transparent gap */
background:linear-gradient(to right,black 10px,transparent 10px,transparent 39px,black 39px) top/100% 1px no-repeat;
}
.box:before {
content: "";
position: absolute;
width: 20px;
height: 20px;
border-top: 1px solid ;
border-left: 1px solid;
top: -11px;
left: 14px;
transform: rotate(45deg);
}
<div class="box">
</div>
这里是虚线边框另一个版本:
body {
margin:0;
background-image:linear-gradient(to right,yellow,pink);
}
.box {
border: 1px dashed;
border-top:transparent; /*make border-top transparent*/
margin: 50px;
height: 50px;
position:relative;
background:
repeating-linear-gradient(to right,black 0,black 3px,transparent 3px,transparent 6px) top left/10px 1px,
repeating-linear-gradient(to right,black 0,black 3px,transparent 3px,transparent 6px) top right/calc(100% - 40px) 1px;
background-repeat:no-repeat;
}
.box:before {
content: "";
position: absolute;
width: 20px;
height: 20px;
border-top: 1px dashed;
border-left: 1px dashed;
top: -11px;
left: 13px;
transform: rotate(45deg);
}
<div class="box">
</div>