From The Battle for Wesnoth Wiki
the [campaign] tag
This tag describes a campaign, and is used for the "Campaign" menu in the title screen.
The [campaign] tag has the following attibutes:
- icon: the image displayed in the campaign selection menu
- name: (translatable) name displayed in the campaign selection menu
- abbrev: (translatable) abbreviation used as a prefix for savefile names made from this campaign
- image: the image shown in the information pane when this campaign is selected in the campaign selection menu
- description: (translatable) text shown in the information pane when this campaign is selected in the campaign selection menu
- define=CAMPAIGN_SYMBOL when this campaign is started, the preprocessor symbol CAMPAIGN_SYMBOL will be defined. See #ifdef in PreprocessorRef for how this can be used to isolate parts of the campaign file from other campaigns. Only the tags [campaign] and [binary_path] (see BinaryPathWML) should go outside of #ifdef CAMPAIGN_SYMBOL. This symbol will be defined before any .cfg is preprocessed.
- extra_defines: a comma(,) separated list of preprocessor symbols. Those symbols will be defined before any .cfg is preprocessed.
- difficulties: a comma(,) separated list of preprocessor symbols, exactly one of which will be stored depending on the difficulty setting chosen when the campaign is started. The symbols EASY, NORMAL, and HARD are usually used, and there are several macros in utils.cfg (see UtilWML) which check for these values to set WML keys to different values depending on difficulty. If you use different difficulty symbols, you may need to define your own versions of these macros.
- difficulty_descriptions: the menu of difficulties; this is a list of descriptions (see DescriptionWML) that correspond to different difficulty levels. Since each description is a menu option for a difficulty level, this must provide the same number of descriptions as there are levels in the difficulties list.
- first_scenario: the ID of the first scenario in the campaign; see id in ScenarioWML
- rank: a number that determines the order of campaigns in the campaign selection menu. Lower rank campaigns appear earlier, with unranked campaigns at the end. Currently the mainline campaigns use multiples of 10 from 0 to 399, with 0-99 for Novice campaigns, 100-199 for Intermediate campaigns, and 200-399 for Expert campaigns; if you specify this, it should not be less than 400. (Note: This replaces an older convention that topped out at 50.)
- [about]: inserts your own credits into the game's list of credits. The campaign's name automatically is inserted at the top of the rolling credits followed by title/text key pairs. There can be any number of [about] tags inside a [campaign] tag. The [about] tag has the following keys:
- title: (translatable) large text used to start a new subsection (writers, artists, units, balancing) in the rolling credits
- text: (translatable, but you probably won't want to make it such) smaller text which is displayed before the contributor names
- [entry]: Contains information about a single contributor. Only the name key will be used in-game, the other three keys are for display on the Credits website.
- name: The name of the contributor
- comment: Optional short note about what that person did
- email: Optional email address
- wikiuser: Optional, the user name on the wiki
The following keys of [campaign] are obsolete and have no effect:
- id: the internationalization key for the campaign