#Flexbox

The Flexbox Layout (Flexible Box) module (currently a W3C Last Call Working Draft) aims at providing a more efficient way to lay out, align and distribute space among items in a container, even when their size is unknown and/or dynamic (thus the word "flex").

CSS Rules for the container

###display This defines a flex container; inline or block depending on the given value. It enables a flex context for all its direct children.

.container {
  display: flex; /* or inline-flex */
}

###flex-direction This establishes the main-axis, thus defining the direction flex items are placed in the flex container. Flexbox is (aside from optional wrapping) a single-direction layout concept. Think of flex items as primarily laying out either in horizontal rows or vertical columns.

.container {
  flex-direction: row | row-reverse | column | column-reverse;
}

• row (default): left to right in ltr; right to left in rtl
• row-reverse: right to left in ltr; left to right in rtl
• column: same as row but top to bottom
• column-reverse: same as row-reverse but bottom to top

###flex-wrap By default, flex items will all try to fit onto one line. You can change that and allow the items to wrap as needed with this property. Direction also plays a role here, determining the direction new lines are stacked in.

.container{
  flex-wrap: nowrap | wrap | wrap-reverse;
}

• nowrap (default): single-line / left to right in ltr; right to left in rtl
• wrap: multi-line / left to right in ltr; right to left in rtl
• wrap-reverse: multi-line / right to left in ltr; left to right in rtl

###flex-flow (Applies to: parent flex container element) This is a shorthand flex-direction and flex-wrap properties, which together define the flex container's main and cross axes. Default is row nowrap.

.container{
  flex-flow: <‘flex-direction’> || <‘flex-wrap’>;
}

###justify-content This defines the alignment along the main axis. It helps distribute extra free space left over when either all the flex items on a line are inflexible, or are flexible but have reached their maximum size. It also exerts some control over the alignment of items when they overflow the line.

.container {
  justify-content: flex-start | flex-end | center | space-between | space-around;
}

• flex-start (default): items are packed toward the start line
• flex-end: items are packed toward to end line
• center: items are centered along the line
• space-between: items are evenly distributed in the line; first item is on the start line, last item on the end line
• space-around: items are evenly distributed in the line with equal space around them. Note that visually the spaces aren't equal, since all the items have equal space on both sides. The first item will have one unit of space against the container edge, but two units of space between the next item because that next item has its own spacing that applies.

###align-items This defines the default behaviour for how flex items are laid out along the cross axis on the current line. Think of it as the justify-content version for the cross-axis (perpendicular to the main-axis).

.container {
  align-items: flex-start | flex-end | center | baseline | stretch;
}

• flex-start: cross-start margin edge of the items is placed on the cross-start line
• flex-end: cross-end margin edge of the items is placed on the cross-end line
• center: items are centered in the cross-axis
• baseline: items are aligned such as their baselines align
• `stretch' (default): stretch to fill the container (still respect min-width/max-width)

###align-content This aligns a flex container's lines within when there is extra space in the cross-axis, similar to how justify-content aligns individual items within the main-axis.

Note: this property has no effect when there is only one line of flex items.

.container {
  align-content: flex-start | flex-end | center | space-between | space-around | stretch;
}

CSS Rules for the flex items

###flex-grow By default, flex items are laid out in the source order. However, the order property controls the order in which they appear in the flex container.

.item {
  order: <integer>;
}

###flex-grow This defines the ability for a flex item to grow if necessary. It accepts a unitless value that serves as a proportion. It dictates what amount of the available space inside the flex container the item should take up.

If all items have flex-grow set to 1, the remaining space in the container will be distributed equally to all children. If one of the children a value of 2, the remaining space would take up twice as much space as the others (or it will try to, at least).

.item {
  flex-grow: <number>; /* default 0 */
}

###flex-shrink This defines the ability for a flex item to shrink if necessary.

.item {
  flex-shrink: <number>; /* default 1 */
}

###flex-basis This defines the default size of an element before the remaining space is distributed. It can be a length (e.g. 20%, 5rem, etc.) or a keyword. The auto keyword means "look at my width or height property" (which was temporarily done by the main-size keyword until deprecated). The content keyword means "size it based on the item's content" - this keyword isn't well supported yet, so it's hard to test and harder to know what it's brethren max-content, min-content, and fit-content do.

.item {
  flex-basis: <length> | auto; /* default auto */
}

###flex This is the shorthand for flex-grow, flex-shrink and flex-basis combined. The second and third parameters (flex-shrink and flex-basis) are optional. Default is 0 1 auto.

.item {
  flex: none | [ <'flex-grow'> <'flex-shrink'>? || <'flex-basis'> ]
}

###align-self This allows the default alignment (or the one specified by align-items) to be overridden for individual flex items.

Please see the align-items explanation to understand the available values.

.item {
  align-self: auto | flex-start | flex-end | center | baseline | stretch;
}

Will & Mehran