Function platform_view 

pub fn platform_view(view_type: impl Into<String>) -> PlatformViewView

Platform-view embedding (platform-views feature): reserve layout space for a native view (a map, a video player, …) composited alongside the frust surface. platform_view takes the "dev.frust.<Factory>"-style native factory name registered on each platform and returns a builder (PlatformViewView) over the params/size contract — flat-re-exported from frust-widgets so app code never names that crate directly.

Paint contract (Mode B)

Under Mode B compositing the frust surface itself is translucent, so any region this slot’s parent doesn’t paint over is a window straight through to the native view (or the OS background) behind it — this is the mechanism Mode B relies on, not a bug. Size/position a slot deliberately, and don’t rely on an unpainted sibling region staying opaque.

Mode B is selected by the generated host’s FRUST_TRANSLUCENT_SURFACE (Android)/translucentSurface (iOS) build-time constant — not from Rust: that constant drives, in one host-glue branch, the native window’s pixel format (PixelFormat.TRANSLUCENT/CAMetalLayer.isOpaque = false), the native-sibling z-order/subview arrangement, and the nativeSetSurfaceMode/frust_set_surface_mode call together (flipping only some of these is a host-template defect). There is no app-Rust opt-in call; the generated project’s template is the sole route into Mode B.

use frust::{AnyView, Column, Component, any, platform_view, text};

#[derive(Default)]
struct MapDemo;

impl Component for MapDemo {
    type State = ();

    fn init(&self) -> Self::State {}

    fn build(&self, _state: &mut Self::State) -> AnyView<Self::State> {
        any(Column(vec![
            any(text("map below")),
            any(platform_view("dev.frust.MapFactory")
                .params_json(r#"{"style":"dark"}"#)
                .size(320.0, 240.0)),
        ]))
    }
}

frust::app!(MapDemo);

Z-shields (shield)

A slot marked .interactive() forwards a touch-DOWN inside its rect to the native view, including one that landed on frust chrome painted over it (the OS-side hit test knows nothing about the frust scene). Wrap that chrome in shield and it keeps winning input: the wrapper reports the rect it painted every frame, and the shell hands the overlapping ones to the host with the slot’s placement. Reserve layout space for a native platform view created by view_type (the "dev.frust.<Factory>" convention), filling its container by default (see [SlotSize::Expand]). See the module docs for the full builder contract.