3.1. Room Descriptions

| Chapter 3: Place |

| 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

> change the printed name of the Church to "Lightning-Struck Ruin";
> change the description of the Church to "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 game 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 game 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 game 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.";
> change the watch to 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 game 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 paragraphs description 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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| Example Ant-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. |
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344
| Example Priority Lab A debugging rule useful for checking the priorities of objects about to be listed. |
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When it comes time to start manipulating the priorities of items, it is useful to be able to check the table for debugging purposes; the problem is that printing the names of the objects can itself affect the way the room description is generated, foiling our debugging efforts. What follows is a rule to help with debugging safely, and a sample of how priorities work: "Priority Lab" Section 1 - Procedure Before printing the locale description (this is the dump locale table rule): say "Locale Priority list:"; repeat through Table of Locale Priorities: let the flag be whether or not the notable-object entry is mentioned; say "[line break] [notable-object entry]: [locale description priority entry]"; if the flag is false, now the notable-object entry is not mentioned; say line break. Now, let's look at some items put in a specific order. Things with low priority numbers list towards the beginning; things with high priority numbers list towards the end. (It helps to think of it as though we were making a numbered list of the paragraphs to appear in the description.) Anything numbered 0 doesn't appear at all, and the default priority of an object is 1. Thus: Section 2 - Scenario The Priority Lab is a room. The early bird, the worm, the leaf, the unseen object, the pebble, the twig, and the late edition are things in the Priority Lab. After choosing notable locale objects: set the locale priority of the early bird to 1; [list before everything else -- this would work with any number lower than 5 and higher than 0] set the locale priority of the unseen object to 0; [don't list at all] set the locale priority of the late edition to 10; [list after everything else -- this would work with any number larger than 5] An important cautionary note: priorities are only honored if the objects are going to get their own paragraphs (with "writing a paragraph about..." or because they have initial appearances). Priorities do not affect the order in which items appear in the final "You can see..." list, except that items with priority 0 or lower are omitted. (If we want to order the items in that list, we may want to resort to the Complex Listing extension by Emily Short.) So in order for the priorities we just set to be interesting, let's give out some initial appearances and writing a paragraph rules: The initial appearance of the worm is "A worm inches along the ground." The initial appearance of the late edition is "Finally, the late edition lies at your feet." Rule for writing a paragraph about the early bird: say "The early bird always appears first, and here it is." Rule for writing a paragraph about the leaf: say "Look, [a leaf]!" This procedure also means (as you can test by experiment) that after the late edition has been picked up and dropped again, it lists in no special order in the "you can see..." paragraph (since initial appearances only print when the object has not yet been moved). The other thing to note is that by default that final collection of generic objects ("You can also see...") appears at the end, regardless of the priority of everything else. If we really wanted to, though, we could force something to appear even after that paragraph, by adding a new listing rule to the locale description rules: The late listing rule is listed after the you-can-also-see rule in the for printing the locale description rules. A thing can be marked for late listing. A thing is usually not marked for late listing. This is the late listing rule: if something is marked for late listing: say "Oh! And also [a list of things which are marked for late listing]."; now everything is not marked for late listing; continue the activity. And now we set up an item to use this: The afterthought is a thing in the Priority Lab. After choosing notable locale objects: if the afterthought is a notable-object listed in the Table of Locale Priorities: now the afterthought is mentioned; now the afterthought is marked for late listing. Test me with "get leaf / drop leaf / look / x unseen object / get pebble / look / get twig / look / get afterthought / look / drop twig / look / get late edition / look".

345
| Example Low Light An object that is only visible and manipulable when a bright light fixture is on. |
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343
| Example The 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. |
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341
| Example Rip 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. |
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348
| Example Copper 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. |
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3
| Example Slightly Wrong A room whose description changes slightly after our first visit there. |
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152
| Example Infiltration A room whose description changes depending on the number of times the player has visited. |
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147
| Example Night Sky A room which changes its description depending on whether an object has been examined. |
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