Why isn't `height: 100%` and absolute positioning working in flexbox? - css

Question

I'm trying to make a child div of a flexbox layout fill its parent. In any other context setting the width/height to 100% causes a div to fill its parent... I only wish to use flexbox for my top level layout.
Problems
#map-container div will not fill #col1 even though it has height 100% set.
#controls div appears outside #col1 completely. I've previously used absolute layout to align boxes to corners without problems. Being inside a flexbox grand-parent seems to cause issues.
What I'm expecting is #map-container and #map to fill #col1 and #controls to align to bottom right-hand corner of #map.
.wrapper, html, body {
height:100%;
margin:0;
}
#col1 {
display: flex;
}
#map-container {
background-color: yellow;
width: 100%;
height: 100%;
}
#map {
background-color: purple;
width: 100%;
height: 100%;
}
#controls {
background-color: orange;
position: absolute;
right: 3px;
bottom: 3px;
width: 100px;
height: 20px;
}
.wrapper {
display: flex;
flex-direction: column;
}
#row1 {
background-color: red;
}
#row2 {
flex:2;
display: flex;
}
#col1 {
background-color: green;
flex: 1 1;
}
#col2 {
background-color: blue;
flex :0 0 240px;
}
<div class="wrapper">
<div id="row1">Header</div>
<div id="row2">
<div id="col1">
<div id="map-container">
<div id="map">
Map
</div>
<div id="controls">Controls</div>
</div>
</div>
<div id="col2">Sidebar</div>
</div>
</div>

Answer 1

#map-container div will not fill #col1 even though it has height 100% set.
It won't work that way, because for a percentage unit to work, it needs to have height set on its parent all the way up. This fights against the flex model, where the flex-items are distributed and arranged by the flex-box layout and have no dimensions set. Why use a flex layout when all your elements are 100%? Either do a 100% on all your element all the way up, or do a flex on all containers.
If you stick to flex layout, then you will have to get into nested flex. Otherwise, you will get #map-container to fill-up, but not the #map.
This fiddle http://jsfiddle.net/abhitalks/sztcb0me illustrates that problem.
#controls div appears outside #col1 completely. I've previously used absolute layout to align boxes to corners without problems. Being
inside a flex-box grand-parent seems to cause issues.
The only issue is that you are positioning it absolutely, but in relation to what? You need to position your #map-container relatively for that to work.
Here is how:
Fiddle: http://jsfiddle.net/abhitalks/sztcb0me/1/
Snippet:
* { box-sizing: border-box; padding: 0; margin: 0; }
html, body, .wrapper { height:100%; width: 100%; }
.wrapper { display: flex; flex-direction: column; }
#row1 { flex: 0 1 auto; background-color: red; }
#row2 { flex: 2 0 auto; display: flex; }
#col1 { flex: 1 0 auto; display: flex; background-color: green; }
#col2 { flex: 0 0 240px; background-color: blue; }
#map-container {
flex: 1 0 auto; display: flex;
position: relative; background-color: yellow;
}
#map { flex: 1 0 auto; background-color: purple; }
#controls {
background-color: orange;
position: absolute;
right: 3px; bottom: 3px;
width: 100px; height: 20px;
}
<div class="wrapper">
<div id="row1">Header</div>
<div id="row2">
<div id="col1">
<div id="map-container">
<div id="map">
Map
</div>
<div id="controls">Controls</div>
</div>
</div>
<div id="col2">Sidebar</div>
</div>
</div>

Answer 2

the problem is that it's wrapped in #map-container
.wrapper, html, body {
height:100%;
margin:0;
}
#col1 {
display: flex;
}
#map-container {
background-color: yellow;
width: 100%;
height: 100%;
}
#map {
background-color: purple;
width: 100%;
/* height: 100%; */
display: flex;
flex-wrap: wrap-reverse;
justify-content: space-between;
}
#controls {
background-color: orange;
position: relative;
/*right: 3px;
bottom: 3px;*/
width: 100px;
height: 20px;
}
.wrapper {
display: flex;
flex-direction: column;
}
#row1 {
background-color: red;
}
#row2 {
flex:2;
display: flex;
}
#col1 {
background-color: green;
flex: 1 1;
}
#col2 {
background-color: blue;
flex :0 0 240px;
}
<div class="wrapper">
<div id="row1">Header</div>
<div id="row2">
<div id="col1">
<!-- <div id="map-container"> -->
<div id="map">
Map
<div id="controls">Controls</div> <!-- add it here -->
</div>
<!-- <div id="controls">Controls</div> -->
<!--</div> -->
</div>
<div id="col2">Sidebar</div>
</div>
</div>
adding an absolute position controls in that way is not optimal (in the snippet I commented it out) ; you can place the controlsnested in #map (and use flex properties for correcting placement)