Window safe-area insets

Argui exposes argui_core::Insets as renderer-independent window geometry. WindowEnvironment::safe_area_insets makes it available to AppModel::view and Render through Context::environment(). Values use logical pixels, matching Argui layout coordinates. Element::safe_area(insets) wraps an element with padding on those four edges, moving the child content into the safe region. It copies the element's background onto the wrapper so that background can continue under transparent system bars while text and controls remain inset. The containing window still needs to draw edge to edge on the platform.

On Android, the platform bridge reads getRootWindowInsets() from the active NativeActivity decor view. Android 11 and later supply system-bar and display-cutout insets through WindowInsets.Type; older releases use the available legacy inset API. The runtime samples after each platform event batch because Winit consumes Android content-rect changes without forwarding a separate event. It also refreshes on creation, resize, scale-factor changes, and redraws. On iOS, it compares the Winit outer window bounds with the safe-area bounds returned by inner_position() and inner_size(). The renderer and layout viewport use the full iOS outer size; safe-area padding is applied only when the app calls Element::safe_area. Other Winit backends default to zero because Winit does not expose a portable safe-area query there.

WindowConfig::with_safe_area_insets supplies an explicit override. An app can also change or clear the override at runtime with AppCommand::SetSafeAreaInsets; passing None restores native detection where supported and zero elsewhere. This gives browser and custom native adapters the same injection API.

The host exposes the safe rectangle reported by its platform; Argui does not label the cause of an Android inset or synthesize browser CSS viewport values. A browser adapter can read those values and pass them through the same command. Convert physical measurements to logical pixels before injecting them.

Apply the reported insets with Element::safe_area(environment.safe_area_insets) when building a window view. The mobile guide shows a complete Rust function using this API.