npm package: @loipham/material-density
Description: Density utilities for Material Components for the web
Latest version: 14.0.4

<!--docs:
title: "Density"
layout: detail
section: components
excerpt: "Density subsystem provides adaptive layout to components."
path: /catalog/density/
-->

# Density

Density subsystem provides adaptive layout to components. Material Design uses low-density space by default but offers high-density space when it improves the user experience. Components with high density enable users to process and take action against large amounts of information in a more manageable way. List, tables, and long forms are components that benefit from increased density.

## Design & API Documentation

<ul class="icon-list">
  <li class="icon-list-item icon-list-item--spec">
    <a href="https://material.io/design/layout/applying-density.html">Material Design guidelines: Applying density</a>
  </li>
  <li class="icon-list-item icon-list-item--link">
    <a href="https://glitch.com/~material-density" target="_blank">Demo: Glitch</a>
  </li>
</ul>

## Installation

```
npm install @loipham/material-density
```

> NOTE: You do not need to directly depend on `@loipham/material-density`, use component provided density Sass mixins instead.

## Basic Usage

The styles for applying density to button component instance looks like this:

```scss
@use "@loipham/material-button";

.my-custom-button {
  // Sets button density scale to `-3`, i.e. button height to `24px`.
  @include button.density(-3);
}
```

This would apply `-3` (high density) to button component instance.

> You would indirectly use the Density API through respective component's mixin which takes care of setting appropriate
> component height.

Here are the components that do provide density Sass mixins:

  * [Button](../mdc-button/README.md#sass-mixins)
  * [Checkbox](../mdc-checkbox/README.md#sass-mixins)
  * [Chip](../mdc-chips/README.md#sass-mixins)
  * [Data Table](../mdc-data-table/README.md#sass-mixins)
  * [Icon Button](../mdc-icon-button/README.md#sass-mixins)
  * [List](../mdc-list/README.md#sass-mixins)
  * [Radio](../mdc-radio/README.md#sass-mixins)
  * [Switch](../mdc-switch/README.md#sass-mixins)
  * [Tab Bar](../mdc-tab-bar/README.md#sass-mixins)
  * [Text Field](../mdc-textfield/README.md#sass-mixins)

## Density Mixins

Components that supports density provides Sass mixins to customize density for that component. Each density mixin takes in a density scale number, e.g. 0 (the default) or -1 (higher density).

Currently, the density system only allows negative numbers to customize for high density. The lower the density scale, the higher the component density. The exact density scale range depends on the component. If the scale number is unsupported by the component density mixin, the compiler will report an error at build time.

The height or size of a component is calculated with the following formula:

```scss
@use "@loipham/material-button";
@use "@loipham/material-density";

$height: button.$height + density.$interval * $density-scale
/// @example 36px + 4px * (-3) => 24px
```

The density interval is set to 4px for visual consistency.

It is recommended to customize density via the provided density mixins, rather than arbitrarily applying component height.

NOTE: Touch targets are automatically disabled when density mixins are applied, since dense components should be optionally enabled and therefore do not have the same default accessibility requirements.

## Component variants

Components that has different variants may have their own density mixin.

For example, Tab Bar has two density mixins:

  * `tab-bar.density()`: Density mixin for standard tab bar.
  * `tab-bar.stacked-density()`: Density mixin for tab bar that has icon stacked on top of label.

Similarly, text field provides 3 different density mixins based on its variant.

## Nested components

Material component that renders another component inside it needs set its own density scale accordingly. Applying density mixin on parent component does not automatically apply density to its children.

For example, Applying density to data table does not automatically set density scale to row checkbox. You'll have to explicitly set density scale to its children. This'll allow clients to have full control on the layout.

## Style Customization

This package is used as utility for other components' density mixins. Customizations provided by this package is not intended to
be consumed directly by developers, use component's density mixin instead.

### Sass Variables

Variable | Description
--- | ---
`$interval` | Density interval between each dense scale. This interval is used for numbered density scale to calculate dense height based on baseline component height.
`$minimum-scale` | Minimum scale supported by density subsystem. This scale always maps to highest dense scale.
`$maximum-scale` | Maximum scale supported by density subsystem. This scale always maps to lowest dense scale.
`$supported-scales` | Supported density scale when density literal is used (For example, `minimum`).

### Sass Functions

Function | Description
--- | ---
`prop-value($density-config, $density-scale, $property-name)` | Returns component property value based on given density config and density scale.