Does anyone have a suggestions on how I could make this a re

Question

Does anyone have a suggestions on how I could make this a reusable component modifier

Adam Powell · Answer

That looks pretty unstable at a minimum it creates a data dependency where composition depends on layout which will never resolve in a single frame What are you trying to do

dazza5000 · Answer

you can see what I am trying to do in the original thread <https kotlinlang slack com archives CJLTWPH7S p1649264638345149>

Adam Powell · Answer

ok so it s predicated on misuse of LazyRow This is a dead end you re not going to be able to implement something free of jank edge cases this way since you re depending on backtracking in both composition and layout that can t happen within a single frame It s going to lead to flickering UIs and it will be difficult to test

Adam Powell · Answer

If you re using this modifier on multiple row children then that s where the backtracking within layout comes from even if the backtracking in composition is resolved

Adam Powell · Answer

even if you could resolve the layout backtracking part you would still get a UI where the user could scroll the row and suddenly its height would grow mid scroll

Kirill Grouchnikov · Answer

If the content is loaded lazily how do you know the max height of yet unloaded elements

Adam Powell · Answer

exactly you don t

Adam Powell · Answer

now presuming you re determined enough to ignore all of the above and do it anyway you can use `Modifier layout` instead of `defaultMinSize` so that you can work in pixels rather than having to consult `LocalDensity` then you could factor out an explicit hoisted state object to hold the max passing that same hoisted state object any time you use the modifier Custom modifiers are written using extension functions so you could do ```fun Modifier myJumpyHeight state MyJumpyHeightState = onSizeChanged layout ```

dazza5000 · Answer

i am determined to ignore all common sense and warnings

Adam Powell · Answer

so long as we re on the same page there smile

dazza5000 · Answer

indeed slightly smiling face

dazza5000 · Answer

another noob question does the state object need to have any characterists interfaces implemented to be persisted across composition or to just be `remembered` when defined

dazza5000 · Answer

like it doesn t need to have it s properties in saver or anything special or does it

Adam Powell · Answer

only if you want it to Its properties that you want to be observable and cause relayout recomposition should be `by mutableStateOf` etc but other than that nothing special

dazza5000 · Answer

I didn t migrate to use layout yet but this is what I have so far

dazza5000 · Answer

```fun Modifier myJumpyHeight state MyJumpyHeightState density Density = onSizeChanged size gt val itemHeight = with density val height = size height height toDp if itemHeight gt state minHeight 0 dp state minHeight = itemHeight defaultMinSize minHeight = state minHeight Dp Unspecified data class MyJumpyHeightState var minHeight Dp = null ```

dazza5000 · Answer

and it works

dazza5000 · Answer

I define these in a parent composable ``` val density = LocalDensity current var myJumpyHeightState by remember mutableStateOf MyJumpyHeightState ```

dazza5000 · Answer

and then pass it in as a modifier of an item that is part of a `LazyRow`

Adam Powell · Answer

never use a `var` in a `data class` constructor param compose or no compose it means you have unstable equality and hash codes over time The former you can rationalize in some circumstances the latter is a Problem TM if someone ever uses one as the key in a map

Adam Powell · Answer

you ll want that to be defined as ```class MyJumpyHeightState minHeight Int = 0 var minHeight by mutableStateOf minHeight ```

Adam Powell · Answer

and then use `val myJumpyHeightState = remember MyJumpyHeightState ` instead of the external `mutableStateOf`

dazza5000 · Answer

sorry for reviving this but are there any new solutions for this that have been developed in the past year