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Chapter 3: Place

§3.1. Room Descriptions; §3.2. Map; §3.3. Position Within Rooms; §3.4. Continuous Spaces and The Outdoors; §3.5. Doors, Staircases, and Bridges; §3.6. Windows; §3.7. Lighting; §3.8. Sounds; §3.9. Passers-By, Weather and Astronomical Events

arrow-up-left.png Contents of The Inform Recipe Book
arrow-left.png Chapter 2: Adaptive Prose
arrow-right.png Chapter 4: Time and Plot
arrow-down-right.png Indexes of the examples

§3.1. Room Descriptions

The printing of a room description is a more delicate business than it might initially seem to be: Inform has to consider all the objects that the player might have brought into the room or dropped there, and all the objects on visible supporters, and decide how to group and list them.

All of this behavior is handled by the looking command, so we find the relevant rules in the carry out looking rulebook. To go through the elements step by step:

Looking begins by printing the name and description of the room we're in. We can introduce variations into room names and descriptions by changing their printed name and description properties, as in

now the printed name of the Church is "Lightning-Struck Ruin";
now the description of the Church is "The beams overhead have been burnt away and the pews are charred. Only the stone walls remain.";

If we need more drastic effects, we can turn off or change either of these features by altering the rules in the carry out looking rulebook. For instance, to remove the name of the location entirely from room descriptions, we would write

The room description heading rule is not listed in the carry out looking rules.

(A word of warning: there is one other context in which the story prints a room name — when restoring a save or undoing a move. To omit the room title here too, add

Rule for printing the name of a room: do nothing.)

Ant-Sensitive Sunglasses demonstrates how to use activities to make more flexible room description text.

Next, the story determines what items are visible to the player and need to be described. These never include the player himself, or scenery, but other things in the environment will be made "marked for listing". This is also the stage at which Inform chooses the order in which items will be listed.

We are allowed to meddle by changing the priorities of objects, in case we want some things to be described to the player first or last in the room description; Priority Lab goes into detail about how. We can also force things to be left out entirely: Low Light handles the case of an object that can only be seen when an extra lamp is switched on, even though the room is not otherwise considered dark. Copper River implements the idea of "interesting" and "dull" objects: the story determines which items are currently important to the puzzles or narrative and mentions those in the room description, while suppressing everything else.

Then Inform carries out the writing a paragraph about... activity with anything that provides one; anything it prints the name of, it tags "mentioned". Thus

Rule for writing a paragraph about Mr Wickham:
    say "Mr Wickham looks speculatively at [list of women in the location]."

will count Wickham and everyone he looks at as all having been mentioned, and will not refer to them again through the rest of the room description. More complicated uses of writing a paragraph abound. A developed system for handling supporters that don't list contents appears in The Eye of the Idol.

Inform then prints the initial appearances of objects that are marked for listing but not already mentioned; and then it performs the listing nondescript items activity, collating the remaining objects into a paragraph like

You can see a dog, a hen, ...

We can pre-empt items from appearing in this paragraph or change their listing by intervening with a Before listing nondescript items... rule, as in

Before listing nondescript items when the player needs the watch:
    if the watch is marked for listing:
        say "The watch catches your eye.";
        now the watch is not marked for listing.

If we wanted the watch always to be listed this way, it would be better to give it an initial appearance, but for conditional cases, the listing nondescript items activity is a good place to intervene. For instance, Rip uses this activity to incorporate changeable or portable items into the main description text for a room when (and only when) that is appropriate.

The listing nondescript items activity also allows us to replace the "You can see..." tag with something else more fitting, if for instance we are in a dimly lit room.

When the story compiles the list of nondescript items, it adds tags such as "(open)" or "(empty)" or "(on which is a fish tank)" to the names of containers and supporters. We can suppress or change the "(empty)" tag with the printing room description details of activity, as in

Rule for printing room description details: stop.

And we can suppress the "(open)" and "(on which is...)" sorts of tags with the "omit the contents in listing" phrase, as in

Rule for printing the name of the bottle while not inserting or removing:
    if the bottle contains sand, say "bottle of sand";
    otherwise say "empty bottle";
    omit contents in listing.

Finally, the looking command lists visible non-scenery items that sit on scenery supporters, as in

On the table is a folded newspaper.

These paragraphs can be manipulated with the printing the locale description activity and the printing a locale paragraph about activity.

Another common thing we may want to do is change the description of a room depending on whether we've been there before (as in Slightly Wrong) or on how often we've visited (as in Infiltration). Night Sky, meanwhile, changes the description of a room when we've examined another object, so that the player's awareness of his environment is affected by other things the character knows.

* See Looking for ways to change the default length of room descriptions

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*ExampleNight Sky
A room which changes its description depending on whether an object has been examined.

A room whose description changes depending on the number of times the player has visited.

*ExampleAnt-Sensitive Sunglasses
What are activities good for? Controlling output when we want the same action to be able to produce very flexible text depending on the state of the world -- in this case, making highly variable room description and object description text.

*ExampleRip Van Winkle
A simple way to allow objects in certain places to be described in the room description body text rather than in paragraphs following the room description.

*ExamplePriority Lab
A debugging rule useful for checking the priorities of objects about to be listed.

*ExampleLow Light
An object that is only visible and manipulable when a bright light fixture is on.


**ExampleSlightly Wrong
A room whose description changes slightly after our first visit there.

**ExampleThe Eye of the Idol
A systematic way to allow objects in certain places to be described in the room description body text rather than in paragraphs following the room description, and to control whether supporters list their contents or not.

***ExampleCopper River
Manipulating room descriptions so that only interesting items are mentioned, while objects that are present but not currently useful to the player are ignored.