Element with cut corner and semi-opaque background

Question

I need to create a fluid shape with a cut off corner and a border. The shape needs to be able to sit on an unknown background. This in itself isn't an issue but I also need the background of this element/s to be semi-opaque.

Here's what I have so far...

* {
  -webkit-box-sizing: border-box;
  -moz-box-sizing: border-box;
  box-sizing: border-box;
}

body {
    background: pink;
}

.sidebar-widget {
    border: 1px solid #44AAAB;
    border-right: none;
    border-bottom: none;
    position: relative;
    padding: 15px 0 0 15px;
    margin-bottom: 20px;
}

.sidebar-widget .inner {
    position: relative;
    padding: 15px 0 0 15px;
    left: -15px;
    top: -15px;
    background: #f2f2f2;
}

.sidebar-widget .inner:before {
    content: "";
    width: 100%;
    height: 15px;
    background: #f2f2f2;
    border: 1px solid #44AAAB;
    border-right: none;
    border-top: none;
    position: absolute;
    left: -1px;
    bottom: -16px;
}

.sidebar-widget .inner .content:after {
    content: "";
    width: 15px;
    height: 100%;
    background: #f2f2f2;
    border: 1px solid #44AAAB;
    border-left: none;
    border-bottom: none;
    position: absolute;
    right: -16px;
    top: -1px;
}

.corner {
    width: 22px;
    height: 22px;
    border-right: 1px solid #44AAAB;
    background: #f2f2f2;
    position: absolute;
    right: 4px;
    bottom: 4px;
    transform: rotate(45deg);
    z-index: 1;
}

.sidebar-widget.trans-bg .inner,
.sidebar-widget.trans-bg .inner:before,
.sidebar-widget.trans-bg .inner .content:after,
.trans-bg .corner {
    background: rgba(0,0,0,0.5);
}

<div class="sidebar-widget">
    <div class="corner"></div>
    <div class="inner">
        <div class="content">
            Lorem ipsum dolor sit amet, consectetur adipiscing elit. Nam tellus felis, faucibus id velit eget, auctor tristique ex. Pellentesque id dolor risus. Donec tincidunt, nisl id laoreet tristique, ligula magna placerat mi, id congue magna diam ut sem. Aenean ornare eros nec sapien porta, laoreet venenatis est lobortis.
        </div>
    </div>
</div>

<div class="sidebar-widget trans-bg">
    <div class="corner"></div>
    <div class="inner">
        <div class="content">
            Lorem ipsum dolor sit amet, consectetur adipiscing elit. Nam tellus felis, faucibus id velit eget, auctor tristique ex. Pellentesque id dolor risus. Donec tincidunt, nisl id laoreet tristique, ligula magna placerat mi, id congue magna diam ut sem. Aenean ornare eros nec sapien porta, laoreet venenatis est lobortis.
        </div>
    </div>
</div>

This approach works when the element has solid background but as you can see the square element used to create the cut-off corner is clearly visible when using a semi-opaque background. Can anyone think of a way to get around this?

JSFiddle version

Answer 1

For anyone who is interested here is how I ended up doing it.

Wrap the .corner in another element with overflow: hidden;

* {
  -webkit-box-sizing: border-box;
  -moz-box-sizing: border-box;
  box-sizing: border-box;
}

body {
    background: pink;
}

.sidebar-widget {
    border: 1px solid #44AAAB;
    border-right: none;
    border-bottom: none;
    position: relative;
    padding: 15px 0 0 15px;
    margin-bottom: 20px;
}

.sidebar-widget .inner {
    position: relative;
    padding: 15px 0 0 15px;
    left: -15px;
    top: -15px;
    background: #f2f2f2;
}

.sidebar-widget .inner:before {
    content: "";
    width: 100%;
    height: 15px;
    background: #f2f2f2;
    border: 1px solid #44AAAB;
    border-right: none;
    border-top: none;
    position: absolute;
    left: -1px;
    bottom: -16px;
}

.sidebar-widget .inner .content:after {
    content: "";
    width: 15px;
    height: 100%;
    background: #f2f2f2;
    border: 1px solid #44AAAB;
    border-left: none;
    border-bottom: none;
    position: absolute;
    right: -16px;
    top: -1px;
}

.corner-mask {
    width: 15px;
    height: 15px;
    position: absolute;
    right: 0;
    bottom: 0;
    overflow: hidden;
}

.corner {
    width: 22px;
    height: 22px;
    border-right: 1px solid #44AAAB;
    background: #f2f2f2;
    position: absolute;
    right: 4px;
    bottom: 4px;
    -webkit-transform: rotate(45deg);
    -moz-transform: rotate(45deg);
    transform: rotate(45deg);
    z-index: 1;
}

.sidebar-widget.trans-bg .inner,
.sidebar-widget.trans-bg .inner:before,
.sidebar-widget.trans-bg .inner .content:after,
.trans-bg .corner {
    background: rgba(0,0,0,0.5);
}

<div class="sidebar-widget">
    <div class="corner-mask">
        <div class="corner"></div>
    </div>
    <div class="inner">
        <div class="content">
            Lorem ipsum dolor sit amet, consectetur adipiscing elit. Nam tellus felis, faucibus id velit eget, auctor tristique ex. Pellentesque id dolor risus. Donec tincidunt, nisl id laoreet tristique, ligula magna placerat mi, id congue magna diam ut sem. Aenean ornare eros nec sapien porta, laoreet venenatis est lobortis.
        </div>
    </div>
</div>

<div class="sidebar-widget trans-bg">
    <div class="corner-mask">
        <div class="corner"></div>
    </div>
    <div class="inner">
        <div class="content">
            Lorem ipsum dolor sit amet, consectetur adipiscing elit. Nam tellus felis, faucibus id velit eget, auctor tristique ex. Pellentesque id dolor risus. Donec tincidunt, nisl id laoreet tristique, ligula magna placerat mi, id congue magna diam ut sem. Aenean ornare eros nec sapien porta, laoreet venenatis est lobortis.
        </div>
    </div>
</div>

JSFiddle version