svrollbar

svrollbar is the custom scrollbar made by svelte.

• how to install
• examples
• how to use
  • replace window scrollbar
  • make scrollble area
  • replace overflow-based scrollbar
  • integrate 3rd party libraries
• components spec
• how to customize transition
• how to customize style

how to install

npm install svrollbar

examples

example website is here

example svelte REPL is here.

how to use

svrollbar has two components; Svrollbar.svelte and Svroller.svelte. svrollbar is supposed to use with svelte, but if you want, you can use svrollbar without svelte.

replace window scrollbar

if you would like to customize your window scrollbar, you simply write down Svrollbar.svelte with empty properties,

<Svrollbar />

this is equivalent to:

<Svrollbar viewport={document.scrollingElement} contents={document.body} />

yes, you can see the customized scrollbar on the right side of your browser window. please watch out example website to see the live example.

make scrollable area

if you try to make scrollable area within a part of your web site, you may prefer to use Svroller.svelte. the below example shows you the list which has 50 rows in a 10rem x 10rem square scrollable area with the custom scrollbar.

<script lang="ts">
  import { Svroller } from 'svrollbar'

  const items = Array.from({ length: 50 }).map((_, i) => `item ${i}`)
</script>

<Svroller width="10rem" height="10rem">
  {#each items as item (item)}
    <div>{item}</div>
  {/each}
</Svroller>

replace overflow-based scrollbar

on the other hand, it is better to use Svrollbar.svelte if you already have a kind of scrollable viewport or contents.

<script lang="ts">
  import { Svrollbar } from 'svrollbar'

  const items = Array.from({ length: 50 }).map((_, i) => `item ${i}`)

  export let viewport: Element
  export let contents: Element
</script>

<style>
  .wrapper {
    position: relative;
    width: 10rem;
  }

  .viewport {
    position: relative;
    width: 10rem;
    height: 10rem;
    overflow: scroll;
    border: 1px solid gray;
    box-sizing: border-box;

    /* hide scrollbar */
    -ms-overflow-style: none;
    scrollbar-width: none;
  }

  .viewport::-webkit-scrollbar {
    /* hide scrollbar */
    display: none;
  }
</style>

<div class="wrapper">
  <div bind:this={viewport} class="viewport">
    <div bind:this={contents} class="contents">
      {#each items as item (item)}
        <div>{item}</div>
      {/each}
    </div>
  </div>
  <Svrollbar {viewport} {contents} />
</div>

notice, you do not need to specify fixed value to width or height of viewport. you can set min-*, max-*, and any dynamic and reactive value because svrollbar observes both viewport size and its content size by ResizeObserver.

integrate 3rd party libraries

if you would like to integrate svrollbar into some kind of virtual list implemenation such as svelte-virtual-list or svelte-tiny-virtual-list, you can do that in the following way.

<script lang="ts">
  import { onMount } from 'svelte'
  import VirtualList from 'svelte-tiny-virtual-list'
  import { Svrollbar } from 'svrollbar'

  const items = Array.from({ length: 50 }).map((_, i) => `item ${i}`)

  let viewport: Element
  let contents: Element

  onMount(() => {
    viewport = document.querySelector('.virtual-list-wrapper')
    contents = document.querySelector('.virtual-list-inner')
  })
</script>

<style>
  :global(.virtual-list-wrapper) {
    /* hide scrollbar */
    -ms-overflow-style: none !important;
    scrollbar-width: none !important;
  }

  :global(.virtual-list-wrapper::-webkit-scrollbar) {
    /* hide scrollbar */
    display: none !important;
  }

  .wrapper {
    position: relative;
    width: 10rem;
  }
</style>

<div class="wrapper">
  <Svrollbar {viewport} {contents} />
  <VirtualList width="10rem" height={160} itemCount={items.length} itemSize={16}>
    <div slot="item" let:index let:style {style}>
      {items[index]}
    </div>
  </VirtualList>
</div>

components spec

see here.

how to customize transition

since the simple fade animation is really a bore, you can replace the default fade (show/hide) animation with your one. the transition function is compatible with the svelte transition.

<script>
  import { fly } from 'svelte/transition'
  import { Svroller } from 'svrollbar'

  const items = Array.from({ length: 50 }).map((_, i) => `item ${i}`)
  const flyLeft = (node) => fly(node, { x: -160 })
  const flyRight = (node) => fly(node, { x: 30 })
</script>

<Svroller
  width="10rem"
  height="10rem"
  vTrackIn={flyLeft}
  vTrackOut={flyLeft}
  vThumbIn={flyRight}
  vThumbOut={flyRight}>
  {#each items as item (item)}
    <div>{item}</div>
  {/each}
</Svroller>

how to customize style

you can customize svrollbar style with css variables.

variable	default
--svrollbar-track-width	10px
--svrollbar-track-background	initial
--svrollbar-track-radius	initial
--svrollbar-track-opacity	1
--svrollbar-track-shadow	initial
--svrollbar-thumb-width	6px
--svrollbar-thumb-background	gray
--svrollbar-thumb-radius	0.25rem
--svrollbar-thumb-opacity	0.5
--svrollbar-thumb-shadow	initial

<script lang="ts">
  import { Svroller } from 'svrollbar'

  const items = Array.from({ length: 50 }).map((_, i) => `item ${i}`)
</script>

<style>
  .container {
    border: 3px solid #5d7150;
    width: 10rem;

    --svrollbar-track-width: 20px;
    --svrollbar-track-background: #85b4b9;
    --svrollbar-track-opacity: 1;

    --svrollbar-thumb-width: 10px;
    --svrollbar-thumb-background: #d9ab55;
    --svrollbar-thumb-opacity: 1;
  }
</style>

<div class="container">
  <Svroller width="10rem" height="10rem">
    {#each items as item (item)}
      <div>{item}</div>
    {/each}
  </Svroller>
</div>

todos

• always visible scrollbar
• scrollbar fade timeout
• horizontal scroll support
• drop shadow support
• draggable thumb to scroll
• scrollbar show/hide animation
• dynamic resizing
• replace window scrollbar