Extra div causing the image height not scaling properly (display: flex)

Question

I took the code from here. The code is working well but when I added an extra div to wrap the div with class fullwidth, the images height does not scale equally depending on the height of the screen.

This is how it looks originally:

body,
html {
  height: 100%;
}

.fullwidth {
  display: flex;
  flex-direction: column;
  height: 100%;
}

.repeat-x {
  flex: 1;
  background-size: cover;
  background-repeat: no-repeat;
  background-position: center center;
}

.bg-1 {
  background-image: url(http://oi65.tinypic.com/28v4p6u.jpg);
}

.bg-2 {
  background-image: url(http://oi65.tinypic.com/28v4p6u.jpg);
}

.bg-3 {
  background-image: url(http://oi65.tinypic.com/28v4p6u.jpg);
}

<div class="fullwidth">
  <div class="repeat-x bg-1">&nbsp;</div>
  <div class="repeat-x bg-2">&nbsp;</div>
  <div class="repeat-x bg-3">&nbsp;</div>
</div>

After wrapping fullwidth with another div :-

body,
html {
  height: 100%;
}

.fullwidth {
  display: flex;
  flex-direction: column;
  height: 100%;
}

.repeat-x {
  flex: 1;
  background-size: cover;
  background-repeat: no-repeat;
  background-position: center center;
}

.bg-1 {
  background-image: url(http://oi65.tinypic.com/28v4p6u.jpg);
}

.bg-2 {
  background-image: url(http://oi65.tinypic.com/28v4p6u.jpg);
}

.bg-3 {
  background-image: url(http://oi65.tinypic.com/28v4p6u.jpg);
}

<div id="newid">
  <div class="fullwidth">
    <div class="repeat-x bg-1">&nbsp;</div>
    <div class="repeat-x bg-2">&nbsp;</div>
    <div class="repeat-x bg-3">&nbsp;</div>
  </div>
</div>

Answer 1

You can choose one of these to enlarge the #newid to the whole height of the current viewport:

#newid {
  height: 100vh; /* this is how you do it in 2017 */
  height: 100%;
}

For reference: I can highly recommend this post if you wan to dive deeper into css units: CSS Units - What is the difference between vh/vw and %?

Answer 2

Add height: 100% to the newid container - this allows the flexbox to inherit the height of the document.

See demo below:

body,
html {
  height: 100%;
}

#newid {
  height: 100%;
}

.fullwidth {
  display: flex;
  flex-direction: column;
  height: 100%;
}

.repeat-x {
  flex: 1;
  background-size: cover;
  background-repeat: no-repeat;
  background-position: center center;
}

.bg-1 {
  background-image: url(http://oi65.tinypic.com/28v4p6u.jpg);
}

.bg-2 {
  background-image: url(http://oi65.tinypic.com/28v4p6u.jpg);
}

.bg-3 {
  background-image: url(http://oi65.tinypic.com/28v4p6u.jpg);
}

<div id="newid">
  <div class="fullwidth">
    <div class="repeat-x bg-1">&nbsp;</div>
    <div class="repeat-x bg-2">&nbsp;</div>
    <div class="repeat-x bg-3">&nbsp;</div>
  </div>
</div>