Scroll Effect Lazy

Small Compose lib that makes LazyColumn / LazyRow feel a bit rubbery. Scroll fast and the items at the front lag behind a little, like they're on a stretchy band. Nothing weird happens to layout or measuring, it's all just graphicsLayer under the hood.

Install

Distributed via JitPack.

In your settings.gradle.kts:

dependencyResolutionManagement {
    repositories {
        google()
        mavenCentral()
        maven("https://jitpack.io")
    }
}

In your app/library build.gradle.kts:

implementation("com.github.makzimi:scroll-effect-lazy:0.1.0")

Usage

Swap your LazyColumn / LazyRow for the wrapper, toss in a scrollEffect lambda, done:

ScrollEffectLazyColumn(
    scrollEffect = { item -> elastic(item, ElasticStrength.Normal) }
) {
    items(myList) { MyCard(it) }
}

Don't want the effect? Pass null or just leave it out. You're back to a plain lazy list, no overhead.

Custom effects

The built-in elastic() is just one thing you can do. The scrollEffect lambda runs per visible item on every frame, and this inside it is a GraphicsLayerScope, so you can do whatever you want with it.

ScrollEffectLazyColumn(
    // lambda runs per-item, every frame
    scrollEffect = { item ->
        // use the prebuilt rubber band
        elastic(item)

        // or roll your own with anything from item / item.velocity
        // (it's a GraphicsLayerScope, so all the usual stuff is here)
        alpha = 1f - item.velocity.stretch * 0.3f
        rotationZ = item.velocity.direction * 2f
    }
) {
    items(myList) { MyCard(it) }
}

You can also mix: call elastic(item) for the base feel and then layer your own tweaks on top.

Why a whole new composable and not just a `Modifier`?

Short answer: the effect has to touch every item, not the list as a whole. To pull that off we have to sit between you and LazyListScope and wrap each item in its own graphicsLayer. A modifier on the list can't do that, and making you glue a modifier onto every item by hand would be a pain. The lambda also runs on a little custom scope (ScrollEffectScope) that bundles GraphicsLayerScope with list-aware stuff and shortcuts like elastic(), which a regular modifier just can't give you.

API reference