ndv.views #

def get_array_canvas_class(backend: str | None = None) -> type[ArrayCanvas]:
    """Return [`ArrayCanvas`][ndv.views.bases.ArrayCanvas] class for current canvas backend."""  # noqa: E501
    _backend = canvas_backend(backend)
    if _backend not in CANVAS_PROVIDERS:  # pragma: no cover
        raise NotImplementedError(f"No canvas backend found for {_backend}")
    return CANVAS_PROVIDERS[_backend].array_canvas_class()

def get_array_view_class() -> type[ArrayView]:
    """Return [`ArrayView`][ndv.views.bases.ArrayView] class for current GUI frontend."""  # noqa: E501
    return GUI_PROVIDERS[gui_frontend()].array_view_class()

def get_histogram_canvas_class(backend: str | None = None) -> type[HistogramCanvas]:
    """Return [`HistogramCanvas`][ndv.views.bases.HistogramCanvas] class for current canvas backend."""  # noqa: E501
    _backend = canvas_backend(backend)
    if _backend not in CANVAS_PROVIDERS:  # pragma: no cover
        raise NotImplementedError(f"No canvas backend found for {_backend}")
    return CANVAS_PROVIDERS[_backend].histogram_canvas_class()

@cache  # not allowed to change
def gui_frontend() -> GuiFrontend:
    """Return the active [`GuiFrontend`][ndv.views.GuiFrontend].

    This is determined first by the `NDV_GUI_FRONTEND` environment variable, after which
    known GUI providers are tried in order until one is found that is either already
    running, or available.
    """
    requested = os.getenv(GUI_ENV_VAR, "").lower()
    valid = {x.value for x in GuiFrontend}
    if requested:
        if requested not in valid:
            raise ValueError(
                f"Invalid GUI frontend: {requested!r}. Valid options: {valid}"
            )
        key = GuiFrontend(requested)
        # ensure the app is created for explicitly requested frontends
        provider = GUI_PROVIDERS[key]
        if not provider.is_running():
            provider.create_app()
        return key

    for key, provider in GUI_PROVIDERS.items():
        if provider.is_running():
            return key

    errors: list[tuple[GuiFrontend, BaseException]] = []
    for key, provider in GUI_PROVIDERS.items():
        try:
            provider.create_app()
            return key
        except Exception as e:
            errors.append((key, e))

    raise RuntimeError(  # pragma: no cover
        f"Could not find an appropriate GUI frontend: {valid!r}. Tried:\n\n"
        + "\n".join(f"- {key.value}: {err}" for key, err in errors)
    )

def run_app() -> None:
    """Start the active GUI application event loop."""
    GUI_PROVIDERS[gui_frontend()].exec()