BuildingCampaignsTheCampaignFile
Each campaign must contain a WML file which begins with a [campaign] tag. This file contains the information the game needs to find the rest of the bits of your campaign scattered in other files and put them together to have a playable campaign. Much information about this file can be found in the CampaignWML entry. What follows is a description of each line of the campaign file and an explanation of what it does.
For our purposes I'll assume we've already created a campaign called simple_campaign with the directory structure outlined in BuildingCampaignsDirectoryStructure.
The first line of the campiagn file is the [campaign] WML tag that lets the game know this is a campaign:
[campaign]
The next group of lines uniquely identifies the campaign:
name= _ "A Simple Campaign"
define= CAMPAIGN_SIMPLE_CAMPAIGN
[In earlier version, there was also id which was a unique identifier used for translation, but now has no effect.]
name is the name of your campaign that the user will see. It must be in quotation marks and be preceded by an underscore to facilitate translation. define creates a key that lets the game know when a user has selected to play a scenario from your campaign. More on it in a bit. If you are missing any of these your campaign will not work correctly.
The next group gives the user information about your campaign when he selects it from the campaign menu:
icon=a_wesnoth_icon.png
image= simple_campaign_logo.png
description= _ "Some text about my campaign!"
icon is a reference to any of the standard Wesnoth images. It will be displayed in the campaign selection menu. image is an image that will be displayed when a user clicks on the campaign. description is a text description that will be shown to the user at the same time as image. Note that none of these three are strictly necessary, but they do make your campaign look nice and professional.
difficulties=EASY,NORMAL,HARD
difficulty_descriptions=*&neutral-peasant.png,Civilian,(trivial);*&human-spearman.png,Soldier,(simple);&human-pikeman.png,Veteran,(easy)
difficulties creates three definitions for three different difficulty levels. For more information on difficulty levels and balancing see BuildingCampaignsBalancing. difficulty_descriptions is currently being modified, and will be different in 0.8.9, so I'm not going to spend a lot of time explaining it until the new syntax is released.
first_scenario=the_first_scenario
first_scenario is a reference to the scenario id of the scenario that you intend to be loaded and played first. This line is essential. Note that while you are debugging and testing your campaign, it's often useful to change this line to the scenario you're working on so you don't have to play through all the scenarios that come before it. (You could also just play through your campaign saving at each level.)
[/campaign]
That's all that needs to be in the [campaign] tag, so we can close it here.
There's more we want to do, though: we've got to tell Wesnoth where our various additional files are located (i.e. our maps, scenarios, units, images, and sounds).
The first bit of code we'll look at in this section is a macro definition:
#define SC_MAP NAME
map_data="{@campaigns/simple_campaign/maps/{NAME}}"
#enddef
The first thing worth noting is that the macro begins with SC_. The SC stands for "simple_campaign", the name of our campaign. It's important that you put a prefix like that in front of your macros so they don't interact badly with other user created campaigns (but only if you put the macros outside the campaign #ifdef). We'll see how to use a macro like this later in the BuildingScenarios section.
You should put everything not in the [campaign] tag inside
#ifdef CAMPAIGN_SIMPLE_CAMPAIGN ... #endif
so that your custom macros, WML code, and inclusion of files do not affect other campaigns and slow the game down. The only exception to this is the [binary_path] tag specifying the path to custom images in your campaign, but you should only put this outside the #ifdef if you need custom images for the campaign selection menu and the difficulty selection menu. Otherwise even this belongs inside the #ifdef.
More to come soon…