Fix WindowState and DialogState savers to not crash on unspecified window/dialog size.

[m-sasha]

Fix WindowState.Saver to correctly save/restore unspecified window size.

Fixes JetBrains/compose-multiplatform#4945

Testing

Manually with

fun main() = singleWindowApplication {
    LazyColumn {
        items(1000) { index ->
            val state = rememberWindowState(size = DpSize.Unspecified)
            Text("$index " + state.size.toString())
        }
    }
}

and also added unit tests for saving/restoring `WindowState` and `DialogState`.

Release Notes

Fixes - Desktop

• Correctly save WindowState with unspecified size instead of crashing.

[iamcalledrob]

Hi, issue submitter here. Amazing turnaround!

It looks like you'll need to apply the same fix in at least rememberDialogState too, which uses the same logic and has the same crash.

[m-sasha]

It looks like you'll need to apply the same fix in at least rememberDialogState too, which uses the same logic and has the same crash.

There doesn't seem to be documentation that DialogState.size can be unspecified, but since it works de-facto, I fixed its saver too.

[igordmn]

There doesn't seem to be documentation that DialogState.size can be unspecified

DialogState indeed doesn't contain it compare to WindowState 🤔. It was an oversight, and it should be in KDoc

[igordmn]

The test doesn't check that state can be restored correctly.

To check that, we need to change the size, and switch back to index = 0

[m-sasha]

I see the need to switch back to index = 0, but why change the size?

The latest commit seems to work (I purposely "broke" restoring in order to test it, and the test fails correctly).

[igordmn]

but why change the size?

If we don't change the size, then we can't be sure that value was restored instead of reusing the initial passed value (or reused the value saved in index=1).

To check it correctly, it seems we need to have the initial size not Unspecified:

        var index by mutableIntStateOf(0)
        lateinit var lastRecomposedState: WindowState
        setContent {
            val saveableStateHolder = rememberSaveableStateHolder()
            saveableStateHolder.SaveableStateProvider(index) {
                val state = rememberWindowState(size = DpSize(10f, 10f))
                lastRecomposedState = sate
            }
        }

        state.size = DpSize.Unspecified
        waitForIdle()
        assertWindowStateEquals(WindowState(size = DpSize.Unspecified), lastRecomposedState)

        index = 1
        waitForIdle()
        assertWindowStateEquals(WindowState(size = DpSize(10f, 10f)), lastRecomposedState)

        index = 0
        waitForIdle()
        assertWindowStateEquals(WindowState(size = DpSize.Unspecified), lastRecomposedState)