cssoverlapdropshadow

CSS Dropshadow issue with two divs overlaying each other

I am having issues trying to get this to work right. The dropshadows overlap each other, and for some reason the subShape div top needs to be top:-1px to align properly with the top of the mainShape. In my actual project, the mainShape size may change dynamically in height/width. I just always want the subShape to always be on the top-right.

Any suggestions?

Here is link to my codepen: https://codepen.io/coderm3/pen/pvvXdQb

* {
  box-sizing: border-box;
}

.mainShape {
  position: relative;
  width: 200px;
  height: 100px;
  margin: 15px;
  background: white;
  padding: 5px;
  border-top-left-radius: 10px;
  border-bottom-left-radius: 10px;
  border-bottom-right-radius: 10px;
  border: 1px solid blue;
}

.subShape {
  position: absolute;
  top: 0px;
  right: -60px;
  width: 60px;
  height: 30px;
  padding: 5px;
  background: white;
  border-top-right-radius: 10px;
  border-bottom-right-radius: 10px;
  border-top: 1px solid blue;
  border-right: 1px solid blue;
  border-bottom: 1px solid blue;

}



.mainShape:after, .subShape:after {
 content:"";
  display:block;
  position:absolute;
  left:0;
  top:0;
  height: 100%;
  width: 100%;
  border-radius: 10px;
  box-shadow: 0px 0px 10px 10px rgba(0, 0, 0, 0.46);
  z-index:-1;
}
<div class="mainShape">
  Text in main shape
  <div class="subShape">
    stuff
  </div>
  <!-- SVG drop shadow using css3: https://stackoverflow.com/a/6094674/2209007 -->
 
</div>

example

Solution

  • you need to reset an offset position from top equal to the border's width, and you may use a drop-shadow() filter to avoid shadows overlapping.

    A css var() can be used to easely reset the border size and offset position

    * {
  box-sizing: border-box;
}

:root {
  --border-size: 1px;
}

.mainShape {
  position: relative;
  width: 200px;
  height: 100px;
  margin: 15px;
  background: white;
  padding: 5px;
  border-top-left-radius: 10px;
  border-bottom-left-radius: 10px;
  border-bottom-right-radius: 10px;
  border: var(--border-size) solid blue;
}

.subShape {
  position: absolute;
  top: calc(var(--border-size) * -1);
  right: -60px;
  width: 60px;
  height: 30px;
  padding: 5px;
  background: white;
  border-top-right-radius: 10px;
  border-bottom-right-radius: 10px;
  border-top: 1px solid blue;
  border-right: 1px solid blue;
  border-bottom: 1px solid blue;

}

.mainShape {
filter:drop-shadow(0 0 5px);
}
    <div class="mainShape">
  Text in main shape
  <div class="subShape">
    stuff
  </div>
  <!-- SVG drop shadow using css3: https://stackoverflow.com/a/6094674/2209007 -->

</div>

    Ressources used: