API Reference

Making (area) shields stop CE Projectiles

If you want to stop CE Projectiles in flight, there are a couple extra steps relative to stopping normal projectiles. First, CE Projectiles are not instances of the normal projectile class, so scanning the map for projectiles will miss them. Second, the fastest projectiles travel more than 1 Cell/tick, so if you check the position of projectiles once a tick, some will leak through. To facilitate detecting and stopping CE Projectiles, you can register a callback which runs each time a CE projectile moves.

Registration API

BlockerRegistry.RegisterCheckForCollisionCallback

This function registers a callback which direct fire projectiles call to check if a cell is "solid". You'll want to track either the projectile's origin, or it's previous position in order to tell if it crossed an arbitrary line. The function you register must have the signature bool FuncName(ProjectileCE, IntVec3, Thing). If you want to change where the projectile "dies", change its ExactPosition before returning; Return true if the projectile should be removed.

BlockerRegistry.RegisterImpactSomethingCallback

This function registers a callback which indirect fire projectiles call before exploding/hitting something (the ground if nothing else). You'll want to track either the projectile's origin, and its current position in order to tell if it crossed an arbitrary line. The function you register must have the signature bool FuncName(ProjectileCE, Thing). Return true if the projectile should be removed.

Performance

There are lots of CE projectiles flying during a major combat. You want to take reasonable steps to make your callbacks efficient. Do not iterate all things on the map in each invocation. Instead, if you need to know what shields are on the map, either register/unregister them on spawn/despawn, or iterate the map once per tick on the first projectile and cache the result until the next tick.

Example

Here is a trivial example. If you need a more complete example, check out the examples in Source/CombatExtended/Compatibility.

using CombatExtended.Compatibility;
namespace example {
    [StaticConstructorOnStartup]
    class Example {
        static Example() {
            BlockerRegistry.RegisterCheckForCollisionCallback(CheckForCollision);
            BlockerRegistry.RegisterImpactSomethingCallback(ImpactSomethingCallback);
        }
        static bool CheckForCollision(ProjectileCE p, IntVec3 cell, Thing launcher) {
            return false;
        }
        static bool ImpactSomethingCallback(ProjectileCE p, Thing launcher) {
            return false;
        }
    }
}