NutrientBackdropState

The captured backdrop shared between the content that draws it and the chrome that samples it.

Create one with rememberNutrientBackdropState, put nutrientBackdropSource on the com.pspdfkit.jetpack.compose.views.DocumentView to capture, and sample it with NutrientStatusBarScrim or com.pspdfkit.jetpack.compose.toolbar.NutrientDocumentStatusBarScrim. Both sides must be in the same composition and the source must be drawn before the sampler — in a Box that means the document is declared first, which is also the stacking order you want (chrome over content).

Keeping the blur live relies on the two sharing a draw layer, which they do in the layout above: anything that redraws the content redraws that layer as a whole, re-recording source and then re-drawing the sampler from it in the same frame. Separating them with a layer of their own — a Modifier.graphicsLayer, alpha or shadow on an ancestor between them — can leave the sampler holding the frame it last drew. There is deliberately no invalidation signal from the source to the sampler: the source re-records on every frame it draws, so a signal would ask for another draw of the layer that had just drawn it, and the two would spin the frame loop forever.

One state drives one source. Applying nutrientBackdropSource to two composables leaves the scrim sampling whichever drew last.