Mutable drawing element issue

[chihsuanwu]

In contrast to Android, web drawing elements are mutable, which can pose a problem in current implementations.

For instance, an editable Polyline like this:

var data: List<LatLng> by remember // ...
Polyline(
    points = data,
    editable = true,
    // ...
)

When a user edits the polyline, the original data won't change. Althought it's possible to add callbacks to onDragEnd and onMouseUp, this approach deviates from the preferred Compose way of doing things.

[chihsuanwu]

Perhaps we could approach this by creating two composable functions for each editable drawing component: one for a mutable version and one for an immutable version. For example:

// This is the mutable version.
// The polyline state will be updated when it's dragged or edited, similar to the Marker.
val polylineState = rememberPolylineState(/* some init code */)
MutablePolyline(
    state = polylineState,
    draggable = true,
    // ...
)

// This is the immutable version. It's similar to the current version, 
// but draggable/editable is always false, so it's removed from the arguments.
Polyline(
    points = // ...
)

I'm not sure if this is the best solution, but it looks good to me.