I have a `Box` and I want to use `pointerInput` to detect drag gestures inside this box, but I want...

# compose

[dimsuz]

I have a Box and I want to use pointerInput to detect drag gestures inside this box, but I want to ignore cases when drag starts in the smaller child in center of that box. For example box is 400x400.dp and I want to ignore drags coming from within 100x100.dp of its centered child.

How can I achieve this? Use onGlobalLayout to capture the position and size of the child and then in onDrag check if change: PointerInputChange comes from a child area and do not do what I usually do there in this case?

[MR3Y]

You can observe the interactionSource of the child, and do nothing in case it was being dragged:

val interactionSource = remember { MutableInteractionSource() }
val isChildDragged by interactionSource.collectIsDraggedAsState()
Box(
   modifier = Modifier.pointerInput{
   // check if isChildDragged or not
}
) {
    Child(
modifier = Modifier.draggable(
    interactionSource = interactionSource,
    ...
)
)
}

[Zach Klippenstein (he/him) [MOD]]

You don't need onGloballyPositioned for this case, onPlaced is sufficient and much cheaper since you're only using it to grab the LayoutCoordinates and then read it later.

[Zach Klippenstein (he/him) [MOD]]

Then yea you're on the right track, just make sure not to consume the events when you want to ignore them.

[dimsuz]

Thanks for suggestions!

By "not consuming" you mean simply not doing the usual action, or do I have to somehow explicitly state that I do not consume a certain event?

I'm not very familiar with gesture APIs yet...

[Zach Klippenstein (he/him) [MOD]]

When you are processing the events for a drag, you need to explicitly consume them (by calling the consume* methods on the event), so the views underneath you don't process them again.

[Zach Klippenstein (he/him) [MOD]]

This isn't a compose thing, pointer events work this way in views too the api is just different.

[dimsuz]

right, in the View api I was returning true/false from onTouchEvent. In compose I plan to use pointerInput + detectDragGestures . I see that change parameter of the latter has the consume method, so I will play with this! 🙂