app-grid

##<app-grid>

app-grid is a helper class useful for creating responsive, fluid grid layouts using custom properties. Because custom properties can be defined inside a @media rule, you can customize the grid layout for different responsive breakpoints.

Example:

Import app-grid-style.html and include app-grid-style in the style of an element's definition. Then, add the class app-grid to a container such as ul or div:

<template>
  <style include="app-grid-style">

    :host {
      --app-grid-columns: 3;
      --app-grid-item-height: 100px;
    }

    ul {
      padding: 0;
      list-style: none;
    }

    .item {
      background-color: white;
    }

    @media (max-width: 640px) {
      :host {
        --app-grid-columns: 1;
      }
    }

  </style>
  <ul class="app-grid">
    <li class="item">1</li>
    <li class="item">2</li>
    <li class="item">3</li>
  </ul>
</template>

In this example, the grid will take 3 columns per row and only 1 column if the viewport width is smaller than 640px.

Expandible items

In many cases, it's useful to expand an item more than 1 column. To achieve this type of layout, you can specify the number of columns the item should expand to by setting the custom property --app-grid-expandible-item-columns. To indicate which item should expand, apply the mixin --app-grid-expandible-item to a rule with a selector to the item. For example:

<template>
  <style include="app-grid-style">
    :host {
      --app-grid-columns: 3;
      --app-grid-item-height: 100px;
      --app-grid-expandible-item-columns: 3;
    }

    ul {
      padding: 0;
      list-style: none;
    }

    /* Only the first item should expand */
    .item:first-child {
      @apply(--app-grid-expandible-item);
    }
  </style>
</template>

Preserving the aspect ratio

When the size of a grid item should preserve the aspect ratio, you can add the has-aspect-ratio attribute to the element with the class app-grid. Now, every item element becomes a wrapper around the item content. For example:

<template>
  <style include="app-grid-style">

    :host {
      --app-grid-columns: 3;
      /* 50% the width of the item is equivalent to 2:1 aspect ratio*/
      --app-grid-item-height: 50%;
    }

    ul {
      padding: 0;
      list-style: none;
    }

    .item {
      background-color: white;
    }

  </style>
  <ul class="app-grid" has-aspect-ratio>
    <li class="item">
      <div>item 1</div>
    </li>
    <li class="item">
      <div>item 2</div>
    </li>
    <li class="item">
      <div>item 3</div>
    </li>
  </ul>
</template>

Styling

Custom property	Description	Default
--app-grid-columns	The number of columns per row.	1
--app-grid-gutter	The space between two items.	0px
--app-grid-item-height	The height of the items.	auto
--app-grid-expandible-item-columns	The number of columns an expandible item should expand to.	1