如何在三角形内制作边框? [英] How to make border inside triangle?

问题描述

我正在制作带有箭头和边框的块，看起来像

i am making block with arrow and border looks like

我已经尝试过了.

* {
    box-sizing: border-box;
}
.block-arr {
    background: purple;
    margin: 20px;
    margin-right: 100px;
    position: relative;
}

.block-arr .inner {
    min-height: 100px;
    display: flex;
    padding: 20px;
    align-items: center;
    position: relative;
}

.block-arr .inner:after {
    border-top: 50px solid transparent;
    border-bottom: 50px solid transparent;
    border-left: 50px solid purple;
    content: '';
    position: absolute;
    left: 100%;
    top: 0;
}

.block-arr:after {
    border-top: 50px solid transparent;
    border-bottom: 50px solid transparent;
    border-left: 50px solid purple;
    content: '';
    position: absolute;
    left: 100%;
    top: 0;
}

<div class="block-arr">
    <div class="inner">
        <strong>Main Heading</strong>
        <span>Sub Heading</span>
    </div>
</div>

如何制作像图片一样的图块?我们可以使此箭头高度响应吗?

How can i make block like image? And can we make this arrow height responsive?

推荐答案

我会考虑倾斜转换，插入框阴影和某些线性梯度的混合:

I would consider a mix of skew transformation, inset box-shadow and some linear-gradient:

* {
  box-sizing: border-box;
}

.block-arr {
  padding: 50px;
  margin: 20px;
  margin-right: 100px;
  position: relative;
  background: linear-gradient(#fff, #fff)2px 0/2px 100% no-repeat, purple;
  border-left: 2px solid purple;
  z-index: 0;
}

.block-arr:before {
  content: "";
  position: absolute;
  top: 0;
  bottom: 50%;
  left: 0;
  right: 0;
  background: purple;
  border: 5px solid purple;
  border-bottom: none;
  border-left: none;
  box-shadow: -2px 2px 0px #fff inset;
  transform: skew(25deg);
  transform-origin: top left;
  z-index: -1;
}

.block-arr:after {
  content: "";
  position: absolute;
  top: 50%;
  bottom: 0;
  left: 0;
  right: 0;
  background: purple;
  border: 5px solid purple;
  border-top: none;
  border-left: none;
  box-shadow: -2px -2px 0px #fff inset;
  transform: skew(-25deg);
  transform-origin: bottom left;
  z-index: -1;
}

<div class="block-arr">
  <strong>Main Heading</strong>
  <span>Sub Heading</span>
</div>
<div class="block-arr">
  <strong>Main Heading</strong><br/>
  <span>Sub Heading</span>
</div>
<div class="block-arr">
</div>

这是一个压缩程度更高的版本，带有一些CSS变量，可以轻松处理颜色.您还可以执行相同的操作来处理其他变量:

And here is a more compressed version with some CSS variable to easily handle color. You can also do the same to handle others variables:

* {
  box-sizing: border-box;
}

.block-arr {
  --c1:purple;
  --c2:#fff;
  padding: 50px;
  margin: 20px;
  margin-right: 100px;
  position: relative;
  background: linear-gradient(var(--c2), var(--c2))2px 0/2px 100% no-repeat, var(--c1);
  border-left: 2px solid var(--c1);
  z-index: 0;
}

.block-arr:before,
.block-arr:after {
  left: 0;
  right: 0;
  content: "";
  position: absolute;
  background: var(--c1);
  border: 5px solid var(--c1);
  border-left: none;
  z-index: -1;
}

.block-arr:before {
  top: 0;
  bottom: 50%;
  border-bottom: none;
  box-shadow: -2px 2px 0px var(--c2) inset;
  transform: skew(25deg);
  transform-origin: top left;
}

.block-arr:after {
  top: 50%;
  bottom: 0;
  border-top: none;
  box-shadow: -2px -2px 0px var(--c2) inset;
  transform: skew(-25deg);
  transform-origin: bottom left;
}

<div class="block-arr">
</div>

<div class="block-arr" style="--c1:red;--c2:yellow">
  <strong>Main Heading</strong>
  <span>Sub Heading</span>
  <p>And yes it is reponsive and grow when height grow</p>
</div>

奖励

另一种花哨且更复杂的方法，只有线性渐变:

Another fancy and more complex way with only linear-gradient:

* {
  box-sizing: border-box;
}

.block-arr {
  --c1:purple;
  --c2:#fff;
  padding: 50px;
  margin: 20px;
  margin-right: 100px;
  position: relative;
  border:1px solid;
  background:
  linear-gradient(to top left,transparent calc(50% + 4px),var(--c2) calc(50% + 4px),var(--c2) calc(50% + 6px),transparent 0) 100% 100%/50px 50% no-repeat,
  linear-gradient(to bottom left,transparent calc(50% + 4px),var(--c2) calc(50% + 4px),var(--c2) calc(50% + 6px),transparent 0) 100% 0/50px 50% no-repeat,
  linear-gradient(var(--c2),var(--c2)) 4px calc(100% -  4px)/calc(100% - 58px) 2px no-repeat,
  linear-gradient(var(--c2),var(--c2)) 4px 4px/calc(100% - 58px) 2px no-repeat,
  linear-gradient(var(--c2),var(--c2)) 4px 4px/2px calc(100% - 8px) no-repeat,
  linear-gradient(to top left ,transparent 50%,var(--c1) 50%) 100% 100%/50px 50% no-repeat,
  linear-gradient(to bottom left,transparent 50%,var(--c1) 50%) 100% 0/50px 50% no-repeat,
  linear-gradient(var(--c1),var(--c1)) 0 0/calc(100% - 50px) 100%  no-repeat;
}

<div class="block-arr">
</div>

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