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jmancherje
jmancherje

Reputation: 6633

How to build sticky scroll sidebar behavior similar to Facebook feed sidebar

I am working on building sticky sidebar behavior that will run alongside a vertical feed which is very similar to a facebook feed on desktop web. position: sticky works well for the easy use case where the sidebar is shorter than the height of the viewport. However if your sidebar is larger than the viewport the sidebar needs to have some scrolling mechanism so you can see the bottom of the sidebar as you scroll down the feed.

I am trying to recreate the facebook sidebar sticky scroll here.

The best way to understand the desired behavior is to test out your facebook feed and shrink your screen height so that your viewport is smaller than your sidebar height. I'll try to summarize here:

When your viewport is taller than your sidebar (simple case)

  1. The sidebar behaves exactly as you'd expect with position: sticky. The sidebar stays in the same place and follows as you scroll down and up.

When your viewport is smaller than your sidebar

  1. When you scroll down initially the sidebar scrolls with the feed (they appear fixed together)
  2. When you get to the bottom of your sidebar, it then locks at the bottom and as you scroll down more, the sidebar now appears sticky with the bottom fixed
  3. When you now scroll back up, the sidebar once again appears attached to your main feed, and scrolls up with the main feed. Once you hit the top of the sidebar it's then sticky with the top fixed.
  4. So between those two states (top fixed when scrolling up, bottom fixed when scrolling down), the sidebar scrolls in unison with the main feed.

It's a very nice scrolling experience but very hard to recreate.

I have accomplished the states listed in steps 1-3 above by applying position sticky with a top position, and when you scroll down, using scroll events and some viewport/sidebar height calculations to determine the height difference and adjusting the top css value so it locks when the bottom is lined up with the screen (essentially initialTop - (sidebarHeight - viewportHeight). I cannot figure out steps 4, and 5. The best I could do was transition between the two top values depending on your scroll direction but it's a very bad UX.

I have a sandbox example of a layout here: https://codesandbox.io/s/fragrant-microservice-89b7z?fontsize=14&hidenavigation=1&theme=dark

There's a basic layout with 2 columns (left sidebar and main feed). And there's a react component called StickyScroll which wraps around the column and has all the logic to update the top value. This may be a completely wrong start to a good solution, but any help is greatly appreciated.

Upvotes: 0

Views: 1289

Answers (2)

user1031947
user1031947

Reputation: 6664

I was interested in this as well, so I spent some time studying how fb does it.

It's very clever, my hat off to whichever fb dev originally implemented this.

You have to set the top / bottom css properties on the sticky depending on the direction of scroll, and to keep things from jumping around, you also have to calculate the height of an the element above the sticky, based on scrollTop.

Here is a rough example, which demonstrates the logic in action

Upvotes: 3

darkscripter
darkscripter

Reputation: 425

I try to make a mock up by your sandbox code based on facebook redesign 2020.

hope you find the answer here. I like this approach because it's not very complex. More precisely, I use the css solution when I have to create a component similar to the Facebook sidebar.So i'm not using your StickyScroll component. Hope you find something.

Codesandbox Independent Scroll

Upvotes: 1

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