IssueTracker

We will solve it with adding an optional fraction param to methods in the scope: fillParentMaxWidth(fraction: Float)
If users need to get the size of the parent to do more complex calculations it will be currently recommended to use WithConstraints:
WithConstraints {
    LazyColumnFor(myList) {
         // in WithConstraints scope we have maxWidth/maxHeight in Dp
    }
}

Project: platform/frameworks/support
Branch: androidx-master-dev

commit d3a3d65ae39bc35c1c99d1048ea5b6b94d2faa87
Author: Andrey Kulikov <andreykulikov@google.com>
Date:   Tue Nov 03 15:52:31 2020

    Add fractions in LazyItemScope modifiers
   
    Relnote: Similarly to Modifier.fillMaxSize[Width|Height] we now support fractions in Modifier.fillParentMaxSize[Width|Height] inside the scope of LazyColumn/Row
    Test: new tests for both row and column
    Fixes: 166586426
    Change-Id: I797e279db98215aa6f7c3e705f90442b5bf31f99

M       compose/foundation/foundation/api/current.txt
M       compose/foundation/foundation/api/public_plus_experimental_current.txt
M       compose/foundation/foundation/api/restricted_current.txt
M       compose/foundation/foundation/src/androidAndroidTest/kotlin/androidx/compose/foundation/lazy/LazyColumnForTest.kt
M       compose/foundation/foundation/src/androidAndroidTest/kotlin/androidx/compose/foundation/lazy/LazyRowForTest.kt
M       compose/foundation/foundation/src/commonMain/kotlin/androidx/compose/foundation/lazy/CachingItemContentFactory.kt
M       compose/foundation/foundation/src/commonMain/kotlin/androidx/compose/foundation/lazy/LazyItemScope.kt

https://android-review.googlesource.com/1486062