Scale transform causes rendering gap with flex lay

Question

I'm using flex layout in order to render a container div with 3 evenly sized columns. It works just as I'd expect, until I apply a scale transform. When the container is scaled down, thin gaps appear between the content boxes. The issue happens on MacOS Chrome and Safari, but not Firefox. I believe I'm seeing a rendering bug, but wondering if anyone might have ideas for a workaround.

Here's a greatly simplified example which demonstrates the problem in Chrome:

body {
  background: black;
  margin: 0;
}
.scale {
  transform: scale(0.703125);
}
.container {
  display: flex;
  width: 600px;
  height: 200px;
}
.column {
  flex-grow: 1;
  background:#ff0000;
}
.column:nth-child(2) {
  background: #ff3333;
}

<div class="container scale">
  <div class="column"></div>
  <div class="column"></div>
  <div class="column"></div>
</div>
<div class="container">
  <div class="column"></div>
  <div class="column"></div>
  <div class="column"></div>
</div>

Answer 1

One way around it could be to use a background on that element that matches one of the colors, so the background of the page doesn't show between the elements.

body {
  background: black;
  margin: 0;
}
.scale {
  transform: scale(0.703125);
}
.container {
  display: flex;
  width: 600px;
  height: 200px;
}
.column {
  flex-grow: 1;
  background:#ff0000;
}
.column:nth-child(2), .scale {
  background: #ff3333;
}

<div class="container scale">
  <div class="column"></div>
  <div class="column"></div>
  <div class="column"></div>
</div>
<div class="container">
  <div class="column"></div>
  <div class="column"></div>
  <div class="column"></div>
</div>

Answer 2

Consider working around the problem with CSS box shadows.

Here's an example using the spread-radius value of the box-shadow property.

body {
  background: black;
  margin: 0;
}

.container {
  display: flex;
  height: 200px;
}

.column {
  flex-grow: 1;
  background: #ff0000;
}

.scale {
  transform: scale(0.703125);
  overflow: hidden;                 /* new */
}

.scale>div:nth-child(2) {
  box-shadow: 0 0 0 1000px #ff0000; /* new */
}

.column:nth-child(2) {
  background: orange;               /* easier to see */
}

<div class="container scale">
  <div class="column"></div>
  <div class="column"></div>
  <div class="column"></div>
</div>
<div class="container">
  <div class="column"></div>
  <div class="column"></div>
  <div class="column"></div>
</div>

Here's a detailed explanation of how this method works:

• On hover of child, change background color of parent container (CSS only)