How to create a flex item that shrinks before it wraps? - html

Question

As can be seen in this JS-Fiddle, I basically try to use this CSS to create two divs that should fullfill these requirements:
If twice the space of the wider item is available, both should use 50% width (that works)
If not enough space for both items is available, they should wrap (that works)
If enough space is available for both items, but less than twice the width of the wider one, the narrower item should shrink (that does NOT work, it wraps)
I don't understand this behavior, because I have set flex-shrink for the flex items, so they should be able to shrink - but they don't: If the narrower item would be less than 50% wide, it wraps.
.m {
display: flex;
flex-wrap: wrap;
}
.l_1 {
background-color: red;
flex: 1 1 50%;
}
.r_1 {
background-color: yellow;
flex: 1 1 50%;
}
<div class=m>
<div class=l_1>
left_______________________________________________X
</div>
<div class=r_1>
right
</div>
</div>
(Tested on Firefox and Chrome)

Answer 1

The problem is not flex-shrink. The problem is flex-basis. You have it set to 50%.
This means that flex-grow will add free space to the flex-basis, and each item will wrap quickly, before it has an opportunity to shrink.
Switch from flex-basis: 50% to flex-basis: 0.
More specifically, instead of flex: 1 1 50% use flex: 1, which breaks down to this:
flex-grow: 1
flex-shrink: 1
flex-basis: 0
Now flex-grow distributes free space equally – not proportionally – to both items, and they can shrink before they wrap.
(Here's a more in-depth explanation: Make flex-grow expand items based on their original size)
.m {
display: flex;
flex-wrap: wrap;
}
.l_1 {
background-color: red;
flex: 1;
}
.r_1 {
background-color: yellow;
flex: 1;
}
<div class=m>
<div class=l_1>left_______________________________________________X</div>
<div class=r_1>right</div>
</div>
revised fiddle

Answer 2

When wrapping is enabled, it takes the place of shrinking, so where there is a condition that would trigger shrinking, it wraps instead - until there is only one item in the row, and if that's still bigger than the container, then it will shrink.
So, you need to set flex-basis for all boxes to the minimum size that block should be before wrapping. Note: a box will never shrink further than its minimum content width, meaning you can set flex-basis to 0 and it will go by the minimum content width of each box.
Then, if you want the boxes to expand to fill the available space, then use the flex-grow property (first value in flex) to control the relative amount by which each one should grow.

Answer 3

Flex-shrink will not apply with flex-wrap: wrap also applied. It will line wrap instead.
The only exception to this is when you only have one flex item in the row. Then it should allow for flex-shrink to apply.
Perhaps the appropriate fix is to only apply the flex-wrap within a media query, so it only happens in smaller viewports?