New Trait: Sign Language (DeltaV-Station#677)

# Description

**Sign Language** is a 1-point Visual trait that allows you to use
Galactic Sign Language.

## Media


![image](https://github.com/user-attachments/assets/ef9a3ed0-6157-4604-9db4-d7114595195b)


![image](https://github.com/user-attachments/assets/805b4a8f-a2d3-469c-b4ab-e46c787a55b6)


# Changelog

:cl: Skubman
- add: Add a new 1-point trait called Sign Language, a trait that allows
you to communicate in Galactic Sign Language.

---------

Signed-off-by: Angelo Fallaria <[email protected]>

Content.Server/Traits/Assorted/LanguageKnowledgeModifierComponent.cs

@@ -0,0 +1,23 @@
+using Content.Shared.Language;
+using Robust.Shared.Serialization.TypeSerializers.Implementations.Custom.Prototype.List;
+
+namespace Content.Server.Traits.Assorted;
+
+/// <summary>
+///     Used for traits that modify entities' language knowledge.
+/// </summary>
+[RegisterComponent]
+public sealed partial class LanguageKnowledgeModifierComponent : Component
+{
+    /// <summary>
+    ///     List of languages this entity will learn to speak.
+    /// </summary>
+    [DataField("speaks")]
+    public List<string> NewSpokenLanguages = new();
+
+    /// <summary>
+    ///     List of languages this entity will learn to understand.
+    /// </summary>
+    [DataField("understands")]
+    public List<string> NewUnderstoodLanguages = new();
+}

Content.Server/Traits/Assorted/LanguageKnowledgeModifierSystem.cs

@@ -0,0 +1,35 @@
+using System.Linq;
+using Content.Server.Language;
+using Content.Shared.Language.Components;
+
+namespace Content.Server.Traits.Assorted;
+
+public sealed class LanguageKnowledgeModifierSystem : EntitySystem
+{
+    [Dependency] private readonly LanguageSystem _languages = default!;
+
+    public override void Initialize()
+    {
+        base.Initialize();
+        SubscribeLocalEvent<LanguageKnowledgeModifierComponent, ComponentInit>(OnStartup);
+    }
+
+    private void OnStartup(Entity<LanguageKnowledgeModifierComponent> entity, ref ComponentInit args)
+    {
+        if (!TryComp<LanguageKnowledgeComponent>(entity, out var knowledge))
+        {
+            Log.Warning($"Entity {entity.Owner} does not have a LanguageKnowledge but has a LanguageKnowledgeModifier!");
+            return;
+        }
+
+        foreach (var spokenLanguage in entity.Comp.NewSpokenLanguages)
+        {
+            _languages.AddLanguage(entity, spokenLanguage, true, false, knowledge);
+        }
+
+        foreach (var understoodLanguage in entity.Comp.NewUnderstoodLanguages)
+        {
+            _languages.AddLanguage(entity, understoodLanguage, false, true, knowledge);
+        }
+    }
+}

Resources/Locale/en-US/language/languages.ftl

@@ -28,6 +28,9 @@ language-Moffic-description = The language of the mothpeople borders on complete
 language-RobotTalk-name = RobotTalk
 language-RobotTalk-description = A language consisting of harsh binary chirps, whistles, hisses, and whines. Organic tongues cannot speak it without aid from special translators.
 
+language-Sign-name = Galactic Sign Language
+language-Sign-description = GSL for short, this sign language is prevalent among mute and deaf people.
+
 language-Cat-name = Cat
 language-Cat-description = Meow
 
@@ -72,6 +75,3 @@ language-Kobold-description = Hiss!
 
 language-Hissing-name = Hissing
 language-Hissing-description = Hiss!
-
-language-Sign-name = Sign Language
-language-Sign-description = The standard Galactic sign language, used by those that are unable to speak Galactic Common or at all.

Resources/Locale/en-US/traits/traits.ftl

@@ -56,6 +56,11 @@ trait-description-Foreigner =
     For one reason or another you do not speak this station's primary language.
     Instead, you have a translator issued to you that only you can use.
 
+trait-name-SignLanguage = Sign Language
+trait-description-SignLanguage =
+    You can understand and use Galactic Sign Language (GSL).
+    If you are mute for any reason, you can still communicate with sign language.
+
 trait-name-Voracious = Voracious
 trait-description-Voracious =
     Nothing gets between you and your food.

Resources/Prototypes/Traits/skills.yml

@@ -32,6 +32,17 @@
       species:
         - Felinid
 
+- type: trait
+  id: SignLanguage
+  category: Visual
+  points: -1
+  components:
+    - type: LanguageKnowledgeModifier
+      speaks:
+        - Sign
+      understands:
+        - Sign
+
 - type: trait
   id: Voracious
   category: Physical