I was working on a custom composable using `Layout` and noti

Question

I was working on a custom composable using `Layout` and noticed that modifiers like weight weren t being propagated through the constraints inside the `MeasurePolicy` I m wondering what s the best way to handle this so I don t have to manually hardcode weight calculations when I place my composables there Adding a code snippet in the thread

Vinay Gaba · Answer

```Layout content = leading let leadingComposable gt Box modifier = Modifier layoutId leading this BaseRowLayout leadingComposable added a weight to this composable Box modifier = Modifier layoutId content weight 1f this BaseRowLayout content trailing let trailingComposable gt Box modifier = Modifier layoutId trailing this BaseRowLayout trailingComposable measurables constraints gt val contentMeasurable = measurables find it layoutId == content ``` Doing `contentMeasureable width` here gives me the width that it occupies however it doesn t occupy the entire available space that the weight modifier should ve caused it to do so

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

The `weight` modifier is an extension on `ColumnScope` `RowScope` it just gives a parent data to those measurables that Column Row read to use in their internal calculations It doesn t do anything on layout nodes that aren t directly children of Column Row

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

You can define your own `weight` modifiers that you can read in your own layout

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

But if you re hard coding the modifiers inside the layout s content lambda anyway that s all unnecessary Just define the weights in the measure policy based on layout ID

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

gt so I don t have to manually hardcode weight calculations You re already hard coding these by the looks of it just in a slightly different place

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

I would be happy with code that looked like this ``` Measure leading and trailing first so we know how much space is left for content val leadingPlaceable = leading measure constraints val trailingPlaceable = trailing measure constraints leadingPlaceable size Content takes remaining space val contentPlaceable = content measure constraints leadingPlaceable size trailingPlaceable size ``` I think that still reads pretty clearly

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

It looks like you re just re implementing Column Row but I assume your actual layout is doing other stuff so there s a reason for that

Vinay Gaba · Answer

yes its more complicated and its essentially a base row specd using the behavior prescribed by the design system

Vinay Gaba · Answer

gt You re already hard coding these by the looks of it just in a slightly different place This was just for the example won t always be the case I wanted the user to have the flexibility through the composables they are passing through the slots

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

So are your callers passing explicit modifiers for each of the slots

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

Or do you pass a scope receiver to your slots and let them apply whatever modifiers they want to themselves

Vinay Gaba · Answer

Since they are slots in theory they could use any of the modifiers Each slot is scoped to the RowScope so the weight modifier is also available

Vinay Gaba · Answer

I m guessing the paddings don t get added to the constraints either and I ll have to add that manually thinking face

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

I don t see any paddings in your code snippet but `Modifier padding` is an actual layout modifier it has its own measure policy reads constraints and changes them for the modified element That should work

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

Are you creating your own implementation of `RowScope` I m looking at the one from `Row` and it uses a parent data class that s internal so you d have to define your own

Vinay Gaba · Answer

I was using the one from Row itself and that s the problem I encountered it was a private Row Parent Data class so you are right starting to feel like I m creating a custom row and I m not sure if that s what I want to do sweat smile

Vinay Gaba · Answer

the easier solution is obvious but I was trying to come up with something that can handle all my use cases Maybe it doesn t need to be this generic

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

What kind of special behavior does your design system actually require

Vinay Gaba · Answer

tldr needs to make layout decisions based on available space Easiest solution was to simply use `BoxWithConstraint` but I wanted something more performant Some examples are trailing element overflow to the next line when its a wider screen for some components it gets added to the content itself but below it etc

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

I guess you could just wholesale copy paste the Row impl and change it but there s a surprising amount of code there that you d have to maintain