Designing Games with Game Maker - YoYo Games

Rooms
object_is_ancestor(ind1,ind2) Returns whether object ind2 is an
ancestor of object ind1.
The following functions will give you information about a room:
room_exists(ind) Returns whether a room with the given index exists.
room_get_name(ind) Returns the name of the room with the given index.
Note that, because rooms change during the playing of the room, there are other routines to
get information about the contents of the current room.
Changing resources
This functionality is only available in the Pro Edition of Game Maker.
It is possible to create new resources during the game. Also you can change existing
resources. This chapter describes the possibilities. Be warned though. Changing resources
easily leads to serious errors in your games!!! You must follow the following rules when
changing resources:
• Don't change resources that are being used. This will lead to errors! For example,
don't change a sprite that is being used by an instance.
• When you save the game during playing, added and changed resources are NOT
stored with the save game. So if you load the saved game later, these might not be
there anymore. In general, when you manipulate resources you can no longer use the
built-in system for loading and saving games.
• When you restart the game during playing, the changed resources are NOT restored to
their original shape. In general, when you manipulate resources you can no longer use
the action or function to restart the game.
• Resource manipulation can be slow. For example, changing sprites or backgrounds is
relatively slow. So don't use it during the game play.
• Creating resources during game play (in particular sprites and background) easily uses
huge amount of memory. So be extremely careful with this. For example, if you have
a 32 frame 128x128 animated sprite and you decide to create 36 rotated copies of it
you will use up 36x32x128x128x4 = 72 MB of memory!