Function from_system 

pub fn from_system() -> Result<NativeTheme>

Read the current system theme, auto-detecting the platform and desktop environment.

Platform Behavior

• macOS: Calls from_macos() when the macos feature is enabled. Reads both light and dark variants via NSAppearance.
• Linux (KDE): Calls from_kde() when XDG_CURRENT_DESKTOP contains “KDE” and the kde feature is enabled.
• Linux (other): Returns the bundled Adwaita preset. For live GNOME portal data, call from_gnome() directly (requires portal-tokio or portal-async-io feature).
• Windows: Calls from_windows() when the windows feature is enabled.
• Other platforms: Returns Error::Unsupported.

Errors

• Error::Unsupported if the platform has no reader or the required feature is not enabled.
• Error::Unavailable if the platform reader cannot access theme data.