Jetpack Compose 表面添加自定义阴影

Question

I am trying to develop a custom toolbar in jetpack compose but its shadow is applying to four sides but I want to achieve 3 side shadow(don't needed in top)

Surface(
    shape = RectangleShape,
    color = toolBarBackground(),
    elevation = 12.dp,
) {
    ...
}

I have tried custom shape, but the problem is path must be closed. I have done a simple tick as follows to overcome that but not working(component size itself changing).

private val CustomThreeSideShape = GenericShape { size, _ ->
    moveTo(0f, -100f)
    lineTo(0f, size.height)
    lineTo(size.width, size.height)
    lineTo(size.width, -100f)
    lineTo(0f, -100f)
    close()
}

Answer 1

This is not yet supported, star this issue for updates.

Meanwhile you can use this hack with Modifier.drawWithContent combined with DrawScope.clipRect :

val padding = 20.dp
val density = LocalDensity.current
Surface(
    shape = RectangleShape,
    color = Color.White,
    elevation = 12.dp,
    modifier = Modifier
        .padding(padding)
        .drawWithContent {
            val paddingPx = with(density) { padding.toPx() }
            clipRect(
                left = -paddingPx,
                top = 0f,
                right = size.width + paddingPx,
                bottom = size.height + paddingPx
            ) {
                this@drawWithContent.drawContent()
            }
        }
) {
    Text(
        "Hello",
        modifier = Modifier.padding(10.dp).fillMaxWidth()
    )
}

Result: