.DT exits Discworld Room and Living Help exits Name .SI 5 exits - those handy links to get you from one room to another .EI Description .SP 5 5 Everyone knows what an exit is, except for maybe the most naive newbie. Just about every creator knows how to add basic exits and most know how to do slightly more fancy things with them, such as use exit functions. This document is for those people who want to know the gritty details of how exits actually work, for whatever reason. The rest of this description will be in three parts, describing the roles played by rooms, living objects and the room handler; broadly speaking, rooms store the information for their exits, living objects contain define the action needed for moving and interpret the command according to orientation, if appropriate, and the room handler does all of the actual work. Note: It is not expected that after reading this document, you will be an instant master of the mudlib details of exits. You are expected to spend time correlating the information given here with the relevant code, the file containing the code being given with each section below. .EP Rooms (/std/room) .SP 5 5 There are three variables used by rooms to store information to do with exits, with a fourth handling doors. The biggest one is dest_other, which includes just about all of the vital information; it is a mixed array, with the first, third, etc. elements being directions and the second, fourth, etc. elements being arrays of: destination, the optional exit message, obviousness, size, function, the enter message or information used to compose the enter message, whether the exit is relative or not, two elements to do with looking through an exit and the grade of the exit. Directions can also be given aliases, which are alternative commands for taking a particular direction; for instance, if an exit is called "enter shop", an alias of "enter" could be added [with add_alias( "enter", "enter flat" );] so that either could be used to take that exit. With each change to the exits information, a third variable is updated, exits, which contains a simple array of strings, each element being a valid exit command; it contains the full exit name, any aliases for that exit name and any standard abbreviations (e.g. "w" for "west"). To use an exit from this room, the command given (after allowing for reorientation due to an exit being relative) must be on this list. .EP Living Objects (/std/living/living) .SP 5 5 All living objects have a free verb connected to the function exit_command(), which will handle the start of using an exit, if the function decides that the input means that the living object wants to use an exit. After some preliminary variable shuffling to allow for some other uses for this command, the verb is lengthened if appropriate (e.g. "w" is expanded to "west"). Then the verb is compared to the list of valid exits for the room, taking into account the possibility that the exit might be relative and dealing with that as appropriate. If the exit is valid, control is passed to the room handler via the function exit_move(). .EP The Room Handler (/obj/handlers/room_handler) .SP 5 5 At this point, the verb will either be an actual direction or will be the alias for a direction, so expand_alias() is called on the room to convert the alias, if it is an alias, to an actual direction; anything that isn't an alias is simply returned unchanged. Then the function set_destination() is called on the room, which is used by some cloned room systems to correctly set exits, following which the room handler obtains a copy of the dest_other array element following the element that is the direction. Just as the destination was checked, the door, if there is one, for that exit is checked, and data on it obtained by the handler; if there is a door, it is dealt with appropriately, the move failing if it cannot be opened. Next the exit function, if there is one, is called, followed by a check to see if the exit is too small to be used. At long last, the living object is actually moved, handling exit and enter messages and objects being dragged if necessary, and, if this move is successful, the living object's immediate followers are moved, after making the appropriate checks with the exit function and size. .EP See also .SI 5 add_exit, modify_exit, remove_exit exit_aliases .EI
