pub fn set_default_theme(theme: Theme)Expand description
Supply the base theme a shell seeds itself with, in place of its built-in
fallback. Call before the first frame — typically from a design-system
plugin’s install().
Unlike crate::theme_override::set_app_theme, this does NOT pin
brightness: the shell’s retained theme object continues to re-derive
light/dark from the platform’s appearance against this same base (see the
module docs’ Precedence section). A late call (after the first frame) takes
effect only if the app later calls clear_app_theme; until then, any
active override dominates.
Callable from any thread (see the module docs’ thread contract); the
process-wide slot is a plain Mutex, not a UI-thread-only primitive.