7. In-game Rooms

A room describes a specific location in the game world. Being an abstract concept, it can represent any area of game content that is convenient to group together. In this lesson we will also create a small in-game automap.

In EvAdventure, we will have two main types of rooms:

• Normal, above-ground rooms. Based on a fixed map, these will be created once and then don’t change. We’ll cover them in this lesson.

• Dungeon rooms - these will be examples of procedurally generated rooms, created on the fly as the players explore the underworld. Being subclasses of the normal room, we’ll get to them in the Dungeon generation lesson.

7.1. The base room

Create a new module evadventure/rooms.py.

# in evadventure/rooms.py

from evennia import AttributeProperty, DefaultRoom

class EvAdventureRoom(DefaultRoom):
	"""
    Simple room supporting some EvAdventure-specifics.
 
    """
 
    allow_combat = AttributeProperty(False, autocreate=False)
    allow_pvp = AttributeProperty(False, autocreate=False)
    allow_death = AttributeProperty(False, autocreate=False)

Our EvadventureRoom is very simple. We use Evennia’s DefaultRoom as a base and just add three additional Attributes that defines

• If combat is allowed to start in the room at all.

• If combat is allowed, if PvP (player vs player) combat is allowed.

• If combat is allowed, if any side is allowed to die from it.

Later on we must make sure our combat systems honors these values.

7.2. PvP room

Here’s a room that allows non-lethal PvP (sparring):

# in evadventure/rooms.py

# ... 

class EvAdventurePvPRoom(EvAdventureRoom):
    """
    Room where PvP can happen, but noone gets killed.
    
    """
    
    allow_combat = AttributeProperty(True, autocreate=False)
    allow_pvp = AttributeProperty(True, autocreate=False)
    
    def get_display_footer(self, looker, **kwargs):
        """
        Customize footer of description.
        """
        return "|yNon-lethal PvP combat is allowed here!|n"

The return of get_display_footer will show after the main room description, showing that the room is a sparring room. This means that when a player drops to 0 HP, they will lose the combat, but don’t stand any risk of dying (weapons wear out normally during sparring though).

7.3. Adding a room map

We want a dynamic map that visualizes the exits you can use at any moment. Here’s how our room will display:

  o o o
   \|/
  o-@-o
    | 
    o
The crossroads 
A place where many roads meet. 
Exits: north, northeast, south, west, and northwest

Documentation does not show ansi colors.

Let’s expand the base EvAdventureRoom with the map.

# in evadventyre/rooms.py

# ... 

from copy import deepcopy
from evennia import DefaultCharacter
from evennia.utils.utils import inherits_from

CHAR_SYMBOL = "|w@|n"
CHAR_ALT_SYMBOL = "|w>|n"
ROOM_SYMBOL = "|bo|n"
LINK_COLOR = "|B"

_MAP_GRID = [
    [" ", " ", " ", " ", " "],
    [" ", " ", " ", " ", " "],
    [" ", " ", "@", " ", " "],
    [" ", " ", " ", " ", " "],
    [" ", " ", " ", " ", " "],
]
_EXIT_GRID_SHIFT = {
    "north": (0, 1, "||"),
    "east": (1, 0, "-"),
    "south": (0, -1, "||"),
    "west": (-1, 0, "-"),
    "northeast": (1, 1, "/"),
    "southeast": (1, -1, "\\"),
    "southwest": (-1, -1, "/"),
    "northwest": (-1, 1, "\\"),
}

class EvAdventureRoom(DefaultRoom): 

    # ... 

    def format_appearance(self, appearance, looker, **kwargs):
        """Don't left-strip the appearance string"""
        return appearance.rstrip()
 
    def get_display_header(self, looker, **kwargs):
        """
        Display the current location as a mini-map.
 
        """
        # make sure to not show make a map for users of screenreaders.
        # for optimization we also don't show it to npcs/mobs
        if not inherits_from(looker, DefaultCharacter) or (
            looker.account and looker.account.uses_screenreader()
        ):
            return ""
 
        # build a map
        map_grid = deepcopy(_MAP_GRID)
        dx0, dy0 = 2, 2
        map_grid[dy0][dx0] = CHAR_SYMBOL
        for exi in self.exits:
            dx, dy, symbol = _EXIT_GRID_SHIFT.get(exi.key, (None, None, None))
            if symbol is None:
                # we have a non-cardinal direction to go to - indicate this
                map_grid[dy0][dx0] = CHAR_ALT_SYMBOL
                continue
            map_grid[dy0 + dy][dx0 + dx] = f"{LINK_COLOR}{symbol}|n"
            if exi.destination != self:
                map_grid[dy0 + dy + dy][dx0 + dx + dx] = ROOM_SYMBOL
 
        # Note that on the grid, dy is really going *downwards* (origo is
        # in the top left), so we need to reverse the order at the end to mirror it
        # vertically and have it come out right.
        return "  " + "\n  ".join("".join(line) for line in reversed(map_grid))

The string returned from get_display_header will end up at the top of the room description, a good place to have the map appear!

• Line 12: The map itself consists of the 2D matrix _MAP_GRID. This is a 2D area described by a list of Python lists. To find a given place in the list, you first first need to find which of the nested lists to use, and then which element to use in that list. Indices start from 0 in Python. So to draw the o symbol for the southermost room, you’d need to do so at _MAP_GRID[4][2].

• Line 19: The _EXIT_GRID_SHIFT indicates the direction to go for each cardinal exit, along with the map symbol to draw at that point. So "east": (1, 0, "-") means the east exit will be drawn one step in the positive x direction (to the right), using the “-” symbol. For symbols like | and “\” we need to escape with a double-symbol since these would otherwise be interpreted as part of other formatting.

• Line 51: We start by making a deepcopy of the _MAP_GRID. This is so that we don’t modify the original but always have an empty template to work from.

• Line 52: We use @ to indicate the location of the player (at coordinate (2, 2)). We then take the actual exits from the room use their names to figure out what symbols to draw out from the center.

• Line 58: We want to be able to get on/off the grid if so needed. So if a room has a non-cardinal exit in it (like ‘back’ or up/down), we’ll indicate this by showing the > symbol instead of the @ in your current room.

• Line 67: Once we have placed all the exit- and room-symbols in the grid, we merge it all together into a single string. At the end we use Python’s standard join to convert the grid into a single string. In doing so we must flip the grid upside down (reverse the outermost list). Why is this? If you think about how a MUD game displays its data - by printing at the bottom and then scrolling upwards - you’ll realize that Evennia has to send out the top of your map first and the bottom of it last for it to show correctly to the user.

7.4. Adding life to a room

Normally the room is static until you do something in it. But let’s say you are in a room described to be a bustling market. Would it not be nice to occasionally get some random messages like

"You hear a merchant calling out his wares."
"The sound of music drifts over the square from an open tavern door."
"The sound of commerse rises and fall in a steady rythm."

Here’s an example of how to accomplish this:

# in evadventure/rooms.py 

# ... 

from random import choice, random
from evennia import TICKER_HANDLER

# ... 

class EchoingRoom(EvAdventureRoom):
    """A room that randomly echoes messages to everyone inside it"""

    echoes = AttributeProperty(list, autocreate=False)
	echo_rate = AttributeProperty(60 * 2, autocreate=False)
	echo_chance = AttributeProperty(0.1, autocreate=False)

	def send_echo(self): 
		if self.echoes and random() < self.echo_chance: 
			self.msg_contents(choice(self.echoes))

	def start_echo(self): 
		TICKER_HANDLER.add(self.echo_rate, self.send_echo)

	def stop_echo(self): 
		TICKER_HANDLER.remove(self.echo_rate, self.send_echo)

The TickerHandler. This is acts as a ‘please tick me - subscription service’. In Line 22 we tell add our .send_echo method to the handler and tell the TickerHandler to call that method every .echo_rate seconds.

When the .send_echo method is called, it will use random.random() to check if we should actually do anything. In our example we only show a message 10% of the time. In that case we use Python’s random.choice() to grab a random text string from the .echoes list to send to everyone inside this room.

Here’s how you’d use this room in-game:

> dig market:evadventure.rooms.EchoingRoom = market,back 
> market 
> set here/echoes = ["You hear a merchant shouting", "You hear the clatter of coins"]
> py here.start_echo() 

If you wait a while you’ll eventually see one of the two echoes show up. Use py here.stop_echo() if you want.

It’s a good idea to be able to turn on/off the echoes at will, if nothing else because you’d be surprised how annoying they can be if they show too often.

In this example we had to resort to py to activate/deactivate the echoes, but you could very easily make little utility Commands startecho and stopecho to do it for you. This we leave as a bonus exercise.

7.5. Testing

Create a new module evadventure/tests/test_rooms.py.

You can find a ready testing module here in the tutorial folder.

The main thing to test with our new rooms is the map. Here’s the basic principle for how to do this testing:

# in evadventure/tests/test_rooms.py

from evennia import DefaultExit, create_object
from evennia.utils.test_resources import EvenniaTestCase
from ..characters import EvAdventureCharacter 
from ..rooms import EvAdventureRoom

class EvAdventureRoomTest(EvenniaTestCase): 

    def test_map(self): 
        center_room = create_object(EvAdventureRoom, key="room_center")
        
        n_room = create_object(EvAdventureRoom, key="room_n)
        create_object(DefaultExit, 
                      key="north", location=center_room, destination=n_room)
        ne_room = create_object(EvAdventureRoom, key="room=ne")
        create_object(DefaultExit,
			          key="northeast", location=center_room, destination=ne_room)
        # ... etc for all cardinal directions 
        
        char = create_object(EvAdventureCharacter, 
					         key="TestChar", location=center_room)					        
		desc = center_room.return_appearance(char)

        # compare the desc we got with the expected description here

So we create a bunch of rooms, link them to one centr room and then make sure the map in that room looks like we’d expect.

7.6. Conclusion

In this lesson we manipulated strings and made a map. Changing the description of an object is a big part of changing the ‘graphics’ of a text-based game, so checking out the parts making up an object description is good extra reading.