Add exact outer and inner shadows

Use elevation for Material or platform elevation semantics and zIndex for sibling order. Use dropShadow(s) or innerShadow(s) only when the design needs exact color, blur, spread, offset, shape, or ordered layers.

Build one exact shadow surface

Give the content and shadows the same explicit shape when their outlines must match. Singular modifiers are one-layer conveniences; plural modifiers retain list order. An empty list is a no-op.

fun UiTreeBuilder.ShadowCard() {
    val cardShape = UiShape.rounded(20.dp)

    Surface(
        modifier = Modifier
            .shape(cardShape)
            .dropShadows(
                shadows = listOf(
                    UiShadow(
                        color = 0x33000000,
                        blurRadius = 12.dp,
                        offsetY = 5.dp,
                    ),
                    UiShadow(
                        color = 0x223B82F6,
                        blurRadius = 18.dp,
                        spreadRadius = 2.dp,
                        offsetX = (-4).dp,
                    ),
                ),
                shape = cardShape,
            )
            .innerShadow(
                shadow = UiShadow(
                    color = 0x44000000,
                    blurRadius = 8.dp,
                    offsetY = 3.dp,
                ),
                shape = cardShape,
            )
            .padding(20.dp),
    ) {
        Text("Exact outer and inner shadows")
    }
}

Outer shadows draw immediately before native child content. Inner shadows draw after the child's background, content, subtree, and foreground, but never enter hit testing. Neither form changes measure or layout, so reserve margin or parent spacing for visible outer blur. Ordinary framework containers permit overflow; Lazy containers intentionally clip at their viewport.

Keep raster work stable

Translation, scale, rotation, alpha, ordinary invalidation, and an unchanged size reuse the same raster identity. Size, density, layout direction, shape, or layer changes create a new identity. Prefer transform and alpha animation; continuously changing blur, spread, shape, or dimensions requires a measured device and memory budget.

Enable and verify the Android backend

Package viewcompose-shadow-android; its service registration enables rendering on first use. Without that artifact, the modifiers are intentional no-ops and the rest of the tree continues to render. Explicit installation is only needed when application startup must determine backend availability before the first decorated node.

Verify Catalog -> Graphics -> Outer shadows, Inner shadows, and Lazy/diagnostics. Confirm layer order, transparent input, expected viewport clipping, and repeated-draw cache hits. Backend selection, cache budgets, platform fallbacks, diagnostics, and benchmark constraints belong to the Shadow Android module manual; renderer ordering and optional-backend ownership belong to Modifier Architecture.