I have some issues with creating a runtime built U...

# compose

[Mikael Alfredsson]

I have some issues with creating a runtime built UI system
the scenario is that I want to “inflate” my custom button that defaults to fillMaxWidth(1f) as long as its not placed inside a Row(). If it’s placed inside a Row() it should instead use .weight(1f) so that several buttons can be shown together on one line.
With the old xml system it was possible to grab the layout object after inflating the button and modify it depending on which class we got back but in Compose this approach does not work. Do we have any solution for this?

[vide]

does something else break if you just use weight(1f) always? you could also pass a modifier for your custom button from the parent:

fun MyButton(modifier: Modifier) = { Box(modifier.[...]) }

[Mikael Alfredsson]

weight(1f) does not exist if the button isn’t known to be inside a Column or Row Scope

[Mikael Alfredsson]

the “parent” is also unknown until I create the button (i’m doing this recursively) so I don’t even know the parent beforehand

[Mikael Alfredsson]

weight is also a different function depending on if its in a columnscope or a rowscope, and as far as i understand it, it has to be known at compiletime?

[vide]

ah yes, that's true

[vide]

how exactly is the parent unknown? can you give an example of the generating code?

[Mikael Alfredsson]

ok, lets try (since it’s quite a framework)
I have a componentFactory with one create method
it also contains a map of all components that I have access to in my framework, driven from a “presenter” class (i.e ButtonPresenter(title:String) -> {MyButton(presenterClass)}

so I parse a Json file, getting all the different presenters in a polymorphic list. In the general case I can just read that list, call the factorys createFromPresenter(presenter) function and it will call the correct component constructor to create for example the button

are you with me so far?

[Mikael Alfredsson]

i.e from knowing the presenter::class I can call a constructor

[Mikael Alfredsson]

val registry = mutableMapOf<KClass<out Presenter>, @Composable (Presenter) -> Unit>()
    registry[ButtonPresenter::class] = { MyButton(it as ButtonPresenter) }

    fun create(presenter:Presenter){
        registry[presenter::class]?.invoke(presenter)
    }

[Mikael Alfredsson]

some presenters can contain childPresenters (i.e a list of presenters) so any component that can act as a group will be calling this create function for all children as well, and now we are in the realm of not knowing (not in the create function anyway)

[ephemient]

make that

@Composable (Presenter, Modifier) -> Unit

then rows can pass down Modifier.weight(1f), others can pass down Modifier, and the mapper builds off of the given modifier

[ephemient]

or is this specific to buttons for some reason?

[Mikael Alfredsson]

and create a “create” function per scope?

[ephemient]

no, why?

[Mikael Alfredsson]

modifier.weight(1f) only exists in row and column scope, trying to call it outside any of those scopes is (as far as i know) not possible

[ephemient]

registry[MyRow::class] = { row, modifier ->
    Row(modifier = modifier) {
        for (child in row.children) {
            registry[child::class]?.invoke(child, Modifier.weight(1f))

[Mikael Alfredsson]

yea, that sounds good, did not think of using the called lambda like that. Thanks.

[vide]

sorry, I managed to tap the wrong emoji on my phone 😅

[ephemient]

that's what I assumed happened. thanks for updating blob ok hand