@wethegit/react-gallery

@wethegit/react-gallery

A slideshow-style gallery component for use in React projects.

• Getting started
  • Starter example
• Custom layouts
• Components and options
  • Gallery
  • GalleryMain
  • GalleryNav
  • GalleryPagination
• Accessibility
• useGallery hook
  • Advanced customization
  • Usage

Features

• Accessibility. Built with careful attention to focus management and assistive technology.
• Fully-customizable layouts, using CSS Custom Properties.
• Provides a custom React hook for accessing gallery data, state, updater functions, and more. Build anything on top of the existing gallery components!

Getting started

Install the package

npm install @wethegit/react-gallery
-or-
yarn add @wethegit/react-gallery

Import the Components and—optionally—the hook.

import {
  Gallery,
  GalleryMain,
  GalleryNav,
  GalleryPagination,
  useGallery,
} from "@wethegit/react-gallery"

Import the base stylesheet

This is an optional step, but it's highly recommended to use the base styles as a starting point. The most straightforward way to do this is to import the stylesheet into your app directly from the /node_modules/@wethegit/react-gallery/dist/ directory, but you can do this in whichever way is preferable within your build system or framework.

// app.js

import "@wethegit/react-gallery/dist/main.css"

Create a simple Gallery

The <Gallery> component is a React context provider, which gives all child components access to relevant data. All child components that need access to gallery data must live within a <Gallery>. Here's an example of a gallery, given the following contrived data GALLERY_ITEMS. This will be explained in detail shortly.

⚠️ Before continuing, make sure you have properly imported the base stylesheet, if you intend to use it.

// some-data.js

export const GALLERY_ITEMS = [
  { image: "/my-image-1.png", alt: "Description of image!", id: 131789 },
  { image: "/my-image-2.png", alt: "Description of image!", id: 235233 },
  { image: "/my-image-3.png", alt: "Description of image!", id: 987432 },
  { image: "/my-image-4.png", alt: "Description of image!", id: 768324 },
]

// your-gallery.js

import { GALLERY_ITEMS } from "./some-data"
import { Gallery, GalleryMain, GalleryNav, GalleryPagination } from "@wethegit/react-gallery"

const YourGallery = () => {
  return (
    <Gallery items={GALLERY_ITEMS}>

      <GalleryMain
        renderGalleryItem={({ item }) => (
          <img src={item.image} alt={item.alt} />
        )}
      />

      <GalleryNav direction={0}>⬅️</GalleryNav>
      <GalleryNav direction={1}>➡️</GalleryNav>

      <GalleryPagination
        renderPaginationItem={({ i }) => (
          <span>{i + 1}</span>
        )}
      />

    </Gallery>
  )
}

export default YourGallery

The first step is to give your data to the <Gallery> component via the items prop. At the very least, items is expected to be an Array. From there, you're free to arrange the child components this package provides as you see fit. Below is a brief description of each of the child components' usage. For a detailed breakdown of this component, jump ahead to the Gallery section.

<GalleryMain> is the primary gallery view where your item data is rendered. It receives a render prop, renderGalleryItem, which exposes a few arguments you can use in the JSX you return: item, i, activeIndex, and active. For a detailed breakdown of this component, jump ahead to the GalleryMain section.

We're using the <GalleryNav> component to define our "next" and "previous" buttons. These components receive a direction prop, which expects either a 1 or a 0, and corresponds to the direction the gallery should move in when the button in question is clicked (where 0 maps to "previous", and 1 maps to "next"). For a detailed breakdown of this component, see the GalleryNav section.

We're also using the <GalleryPagination> component here. If you're not familiar, "pagination" refers to what is often rendered as a set of "dots" below a gallery — but this can be anything (thumbnails, icons, and so on). This component receives the render prop, renderPaginationItem, which exposes a few arguments you can use in the JSX you return: item, i, activeIndex, and active. For a detailed breakdown of this component, jump ahead to the GalleryPagination section.

Custom layouts

Assuming the base stylesheet is being used, the <GalleryMain> component renders as a CSS grid, with a single grid area to house the currently-active item. There are a number of CSS custom properties on the various gallery components, which will allow you to customize the look of the gallery. Most of these properties are used to calculate the horizontal positioning of the gallery items around the main grid cell, and can be adjusted to create many different layout variations. Remove the transform property of a .gallery__item entirely, and you'll get a traditional, stacked gallery.

CSS custom property	Element where defined	Default	Description
--item-width	.gallery	min(75%, 1000px)	The width of the items rendered by <GalleryMain>.
--gap	.gallery	25vw	The horizontal gap between the gallery items.
--active-gap	.gallery	0px	The horizontal gap between the currently-active gallery item and the rest.
--duration	.gallery	0	The duration of the transition between active gallery items.
--touch-offset	.gallery	0	The x-offset of the gallery layout, as a result of a pointermove action.
--position-offset	.gallery	0px	A general x-offset, if needed.
--i	.gallery__item		The index of the gallery item.
--center-offset	.gallery__item		The offset of the item from the "middle" item, in number of items.
--index-offset	.gallery__item		The offset of the item from the active item, in number of items.
--side	.gallery__item		Either -1, 0, or 1; mapping to "left", "center", and "right" of the middle item.
--active	.gallery__item		Either 1 or 0, mapping to true or false.
--x	.gallery__item		The final calculation of a gallery item's x position. Use this as a translateX value when customizing transform properties.
--gap	.gallery__pagination	10px	The CSS grid gap between pagination items.

Components and options

<Gallery>

The parent component for all gallery instances. This serves as a React context provider to its children.

Props:

Prop	Type	Default value	Description
ariaLiveText	String	"Item $i of $t."	aria-live region text, which assistive technologies will announce when the active gallery item changes. More information below.
className	String
draggable	Boolean	true	Allows user to advance the gallery by dragging their finger or pointing device.
items	Array		The gallery data.
loop	Boolean	false	Allows for looping behavior — i.e. when the last gallery item is active, a user can navigate to the "next" slide, which will take them back to the start of the gallery.
onChange	Function		Function to run on gallery state update, as a result of a "next", "previous", or "pagination" action. More information below.
startIndex	Number	0	The index of the gallery item that should be active to start.
visibleRange	Number	-1	The number of gallery items "visible" to the left or right of the active one. This option adds a CSS class to all elements within this range, allowing for layout customization. The default value of -1 specifies that all items are visible, while setting the value to 1 for example, would add the "gallery__item--visible" class those items within immediate proximity to the active item.

ariaLiveText

Per the WAI-ARIA spec, browsers using assistive technology such as screen readers announce content within a DOM element containing the aria-live attribute, anytime it changes. The gallery component's default value for this prop is "Item $i of $t.". The variables $i and $t here correspond to "current index" and "total number of items", and will be replaced with those values when rendered. This level of customization is provided so that you can localize/translate your content with accuracy.

onChange

The onChange callback allows you to run code whenever the active gallery item changes. It receives a single Object as an argument, containing the following properties:

Argument	Type	Description
oldIndex	Number	The index before the onChange function fired.
newIndex	Number	The index after the onChange function fires.
direction	Number	Either 0 or 1, mapping to previous/left or next/right.

<GalleryMain>

The primary gallery body. Must be used within a <Gallery>. Renders an unordered list (<ul>) of your gallery items.

Props:

Prop	Type	Description
className	String
renderGalleryItem	Function	A render prop, returning the JSX to render for each gallery item. More information below.

renderGalleryItem

This render prop wraps its return value in a list item (<li>), and receives a handful of arguments:

Argument	Type	Description
active	Boolean	Whether the current item being iterated over is the active item.
activeIndex	Number	The index of the currently active gallery item.
i	Number	The index of the current item being iterated over.
item	Any	The current item being iterated over, as defined by the Array fed to the <Gallery> component's items prop.

<GalleryNav>

The navigational "next" and "previous" buttons. Must be used within a <Gallery>. You can render your buttons either by passing regular JSX children to them, or by using the renderNavItem render prop.

Props:

Prop	Type	Description
children	JSX	Optional. Pass children to the component to render them as children of the implicit <button> element.
className	String
direction	Number
renderNavItem	Function	Optional. For more control over rendering than the children prop would give you, you have the option to pass JSX to this render prop. More information below.

renderNavItem

This render prop is a nice alternative to simply passing childern to the <GalleryNav>, as it provides you with a handful of arguments, as outlined below:

Argument	Type	Description
activeIndex	Number	The index of the currently-active gallery item.
disabled	Boolean	Whether the nav button is in its disabled state — presumably from <Gallery> having its loop prop set to false. Note that the DOM node attributes disabled and aria-disabled="true" are already added to the rendered button; whereas the purpose of this argument is to allow you to render something different based on that disabled state, or write some other rendering code based on it.

<GalleryPagination>

Renders an unordered list (<ul>) of pagination items. Must be used within a <Gallery>.

Props:

Prop	Type	Description
className	String
renderPaginationItem	Function	A render prop, returning the JSX to render for each pagination item. More information below.

renderPaginationItem

This render prop wraps its return value in a list item (<li>) and a <button>, and receives a handful of arguments:

Argument	Type	Description
active	Boolean	Whether the current pagination item being iterated over corresponds to the active gallery item.
activeIndex	Number	The index of the currently active gallery item.
i	Number	The index of the current pagination item being iterated over.
item	Any	The current pagination item being iterated over, as defined by the Array fed to the <Gallery> component's items prop.

Accessibility

The gallery component handles tabbing, focus management, and live-region announcements out-of-the-box. All relevant patterns used in this component follow the guidelines for carousels as documented by the Web Accessibility Initiative.

That said, you must still code responsibly! Ensure that your gallery contents, nav buttons, and pagination items all have discernible text — whether that be image alt text, or visually-hidden text intended for screen readers (the stylesheet included with the Gallery component inclues a CSS utility class for this: .gallery-util-visually-hidden).

Regarding the ARIA-live text, check out the section on this gallery's ariaLiveText prop.

Reduced motion

For reduced motion implementations, you can detect the user's preference via the matchMedia API, and adjust the CSS custom property, --duration on the .gallery selector. Check out the example below, which adds a style tag to the gallery, and overrides the --duration property based on the preference. You could also do this via a conditional className, if you prefer. An alternative is be to pass this prefersReducedMotion value as a prop, which could be helpful if you use the Styled Components library.

const YourGallery = () => {
  // Get the user's motion preference:
  const prefersReducedMotion = window.matchMedia(
    "(prefers-reduced-motion: reduce)"
  ).matches

  // Create an inline style object
  const style = {
    "--duration": prefersReducedMotion ? "0s" : "0.5s",
  }

  return (
    // Pass the style overrides to the <Gallery> component
    <Gallery items={GALLERY_ITEMS} style={style}>
      <GalleryMain
        renderGalleryItem={({ item }) => <img src={item.image} alt={item.alt} />}
      />
      // ...etc
    </Gallery>
  )
}

useGallery hook

The gallery package exposes a useGallery React hook. It returns a single object, the properties of which are outlined below:

Property	Type	Description
activeIndex	Number	The index of the currently-active gallery item.
draggable	Boolean	The value of the <Gallery>'s draggable prop.
galleryItems	Array	The array of items as passed to the <Gallery>'s items prop.
goToIndex	Function	Receives a single argument (Number), and sets the gallery's active item to the item at that index. Subsequently fires the onChange function, if one exists.
itemNodes	React Ref	A React Ref, the current property of which is bound to an Array of the actual Gallery item DOM nodes.
loop	Boolean	The value of the <Gallery>'s loop prop.
next	Function	Increments the gallery's active index, if possible. Subsequently fires the onChange function, if one exists.
onChange	Function	The value of the <Gallery>'s onChange prop. For more information, refer to the onChange section.
previous	Function	Decrements the gallery's active index, if possible. Subsequently fires the onChange function, if one exists.
previouslyActiveIndex	Number	The index of the previously-active gallery item.
setActiveIndex	Function	Receives a single argument (Number), and sets the gallery's active item to the item at that index. Does not fire the onChange function. It is best to use goToIndex instead.
setPreviouslyActiveIndex	Function	Receives a single argument (Number), and sets the gallery's previously active item index.
setTouchState	Function	State setter function, as defined by React's useState hook. Expects a touchState object — for more information, print the touchState variable returned from this hook in your console.
startIndex	Number	The value of the <Gallery>'s startIndex prop.
swipeThreshold	Number	An integer specifying the minimum number of pixels a user has to drag their pointer before a gallery item change is registered.
touchState	Object	Data pertaining to a pointer action, if the <Gallery>'s draggable prop is set to true. Print this variable to your console for more information.
visibleRange	Number	The value of the <Gallery>'s visibleRange prop.

Advanced customization

As you can see above, many of the properties returned by the useGallery hook provide the lower-level functionality for the gallery itself. You can use this data to create any custom implementation you like, without having to worry too much about what's happening behind the scenes.

Usage

Here's an example of a custom component that uses the useGallery hook to simply render a paragraph with some information about the gallery's current state:

import { useGallery } from "@wethegit/react-gallery"

const GalleryInfo = () => {
  const { activeIndex, previousIndex, loop } = useGallery()

  return (
    <p>
      The gallery's current index is {activeIndex}, its last index was {previousIndex},
      and its <code>loop</code> prop is set to {loop}!
    </p>
  )
}

export default GalleryInfo