I'm planning on filing a bug suggesting that `PointerInputScope.awaitFirstDown` should have an inver...

# compose

[Daniel]

I'm planning on filing a bug suggesting that PointerInputScope.awaitFirstDown should have an inverse, but I wanted to check if anyone saw anything obvious I was missing first.

private suspend fun PointerInputScope.awaitChangedToUp(id: PointerId) {
    awaitPointerEventScope {
        do {
            val event = awaitPointerEvent().changes.fastFirstOrNull { it.id == id }
            event?.consumeAllChanges()
        } while (event?.changedToUp() != true)
    }
}

[Tash]

I think there's a tryAwaitRelease() https://cs.android.com/androidx/platform/frameworks/support/+/androidx-main:compose/[…]ease&ss=androidx%2Fplatform%2Fframeworks%2Fsupport:compose%2F

[Tash]

Not sure if it does exactly what your snippet does 🤔

[Daniel]

Thanks, I didn't notice that's there. Unfortunately it behaves differently from what I want

[Daniel]

But it made me realize that large issue, which is that most of the PointerInputScope functions aren't composable.

tryAwaitRelease works in a detectTapGestures , which loops infinitely looking for tap gestures, making it hard to combine with other detectors

[Tash]

Yeah I'm currently trying to work on something where I need to detect taps vs drags, and perform different things. Haven't spent much time on it, but yeah something like awaitTapUp or something will be useful to combine with await.. + drag { }

[Tash]

Not sure if there's a clean way to do it with current APIs

[Daniel]

Yeah, I have a bunch of states the interaction can be in and my code was getting into a mess. Once I realized I was getting a bunch of concurrency bugs and needed mutexes I decided to rethink

[Daniel]

So I refactored to something like while(true) { await event; when { isStartOfTurn(event) -> awaitTurnOrCancel(event) ...} }

[Daniel]

With standard branching on custom functions on PointerInputScope

[Daniel]

@Tash

[Tash]

Oh I see, that might work! Might have to try out something like this for my use case as well. Wish there was a sample regarding this on cs.android.com 😅

[Daniel]

Here's what I have @Tash https://github.com/danielzfranklin/librereader/blob/paginated-text/android/app/src[…]in/librereader/ui/screen/reader/paginatedText/selectablePage.kt

[Daniel]

I ended up submitting a feature request https://issuetracker.google.com/issues/181577176

[Tash]

Great, thanks for sharing @Daniel ! I see now what you mean with the when statement.

[Tash]

Just curious, I see inside awaitChangedToUp you are doing event?.consumeAllChanges() . Is that being done because you need to consume the up + minute position changes as well?

[Daniel]

This code is a modifier that adds selectability to a page

[Daniel]

Pages also handle other gestures in other places

[Daniel]

The intent of that bit @Tash is that in general gestures I don't handle should be propagated to the page, but gestures that start with a press within the area of the selection should be swallowed

[Daniel]

I'm not sure what you mean by minute

[Daniel]

Hope that makes sense 🙂

[Tash]

I see. Right, by minute position changes I mean the slight pointer slop that happens even as you tap. Looks like we’d want to swallow those as well, which is why it’s doing consumeAllChanges() instead of just consumeDownChange()

[Daniel]

Oh, I didn't even think of that @Tash. I just use consumeAllChanges by default 🙂