Method init_navigation_context

src/navigate.rs:192–235

(&self, context: &mut Context, command: &'static str,
                               nav_state_top: Option<(&NavigationPosition, &'static str)>)

    }

    fn init_navigation_context(&self, context: &mut Context, command: &'static str,
                               nav_state_top: Option<(&NavigationPosition, &'static str)>) {
        context.set_variable("NavCommand", command);

        if command == "WhereAmI" && self.where_am_i == NavigationPosition::default() {
            context.set_variable("NavNode", self.where_am_i.current_node.as_str());
            context.set_variable("NavNodeOffset", self.where_am_i.current_node_offset as f64);
        } else {
            let position = &self.position_stack[self.position_stack.len()-1];
            context.set_variable("NavNode", position.current_node.as_str());
            context.set_variable("NavNodeOffset", position.current_node_offset as f64);
        }

        // get the index from command (e.g., '3' in 'SetPlacemarker3 or MoveTo3' and set 'PlaceMarker' to it's position)
        if command.ends_with(|ch: char| ch.is_ascii_digit()) {
            let index = convert_last_char_to_number(command);
            let position = &self.place_markers[index];
            context.set_variable("PlaceMarkerIndex", index as f64);
            context.set_variable("PlaceMarker", position.current_node.as_str());
            context.set_variable("PlaceMarkerOffset", position.current_node_offset as f64);
        }
           
        context.set_variable("ReadZoomLevel", (if self.mode == "Enhanced" {-1} else {1}) as f64);
        context.set_variable("MatchCounter", 0 as f64);

        if command == "MoveLastLocation" {
            let previous_command = match nav_state_top {
                None => "None",
                Some( (_, previous_command) ) => previous_command,
            };
            context.set_variable("PreviousNavCommand", previous_command);
        }

        // used by nav rules for speech -- needs an initial value so tests don't fail
        context.set_variable("Move2D", "" );
        context.set_variable("SpeakExpression", true );    // default is to speak the expr after navigation
        return;

        fn convert_last_char_to_number(str: &str) -> usize {
            let last_char = str.as_bytes()[str.len()-1];
            assert!( last_char.is_ascii_digit() );
            return (last_char - b'0') as usize;
        }
    }
}

// convert the last digit of a Placemarker command to an integer