Hi! I've noticed that `Modifier.progressSemantics`...

# compose

[Valentin Gusselnikov]

Hi! I've noticed that Modifier.progressSemantics causes recompositions.

I've a custom ProgressIndicator, and if I use Modifier.progressSemantics Android Studio "Layout inspector" shows thousand recompositions.

Is it a bug of "Layout inspector", or it is normal?

[Valentin Gusselnikov]

Every tick of a progress counts as a recomposition. This is with Modifier.progressSemantics

[tad]

I think we'd have to see the code of SegmentedProgressIndicator to know what the ultimate cause is. But you might try replacing that with an indeterminate CircularProgressIndicator just to see if that also recomposes every frame.

[Albert Chang]

It's normal because Modifier.progressSemantics reads the value in the current recomposition scope. This usually shouldn't be a problem because when you draw a progress bar you likely need it to be recomposed anyway. If you want to reduce recomposition, you can use Modifier.semantics(mergeDescendants = true) { progressBarRangeInfo = ... } (see the source of Modifier.progressSemantics).

[Valentin Gusselnikov]

The source code for the SegmentedProgressIndicator is taken from this article. Only code is in this gist.

[Valentin Gusselnikov]

The only diffrence in my verstion is that I've replaced

progress: Float

with

progressProvider: () -> Float

[Valentin Gusselnikov]

If I use what @Albert Chang suggested it works without additional recompositions. So thank you!

@Composable
fun SegmentedProgressIndicator(
    progressProvider: () -> Float,
    numberOfSegments: Int,
    modifier: Modifier = Modifier,
    color: Color = Color.White,
    backgroundColor: Color = color.copy(alpha = BackgroundOpacity),
    progressHeight: Dp = ProgressHeight,
    segmentGap: Dp = SegmentGap
) {
    val gap: Float
    val barHeight: Float
    with(LocalDensity.current) {
        gap = segmentGap.toPx()
        barHeight = progressHeight.toPx()
    }
    Canvas(
        modifier
            .semantics(mergeDescendants = true) {
                progressBarRangeInfo = ProgressBarRangeInfo(progressProvider().coerceIn(0f..1f), 0f..1f, 0)
            }
            .height(progressHeight)
    ) {
        drawSegments(1f, backgroundColor, barHeight, numberOfSegments, gap)
        drawSegments(progressProvider(), color, barHeight, numberOfSegments, gap)
    }
}