Adds jittering. (#4809)

Co-authored-by: Pieter-Jan Briers <pieterjan.briers+git@gmail.com>

Content.Client/Jittering/JitteringSystem.cs

@@ -0,0 +1,103 @@
+using System;
+using System.Collections.Immutable;
+using Content.Shared.Jittering;
+using Robust.Client.Animations;
+using Robust.Client.GameObjects;
+using Robust.Shared.Animations;
+using Robust.Shared.GameObjects;
+using Robust.Shared.IoC;
+using Robust.Shared.Maths;
+using Robust.Shared.Random;
+
+namespace Content.Client.Jittering
+{
+    public class JitteringSystem : SharedJitteringSystem
+    {
+        [Dependency] private readonly IRobustRandom _random = default!;
+
+        private readonly float[] _sign = { -1, 1 };
+        private readonly string _jitterAnimationKey = "jittering";
+
+        public override void Initialize()
+        {
+            base.Initialize();
+
+            SubscribeLocalEvent<JitteringComponent, ComponentStartup>(OnStartup);
+            SubscribeLocalEvent<JitteringComponent, ComponentShutdown>(OnShutdown);
+            SubscribeLocalEvent<JitteringComponent, AnimationCompletedEvent>(OnAnimationCompleted);
+        }
+
+        private void OnStartup(EntityUid uid, JitteringComponent jittering, ComponentStartup args)
+        {
+            if (!EntityManager.TryGetComponent(uid, out ISpriteComponent? sprite))
+                return;
+
+            var animationPlayer = EntityManager.EnsureComponent<AnimationPlayerComponent>(uid);
+
+            animationPlayer.Play(GetAnimation(jittering, sprite), _jitterAnimationKey);
+        }
+
+        private void OnShutdown(EntityUid uid, JitteringComponent jittering, ComponentShutdown args)
+        {
+            if (EntityManager.TryGetComponent(uid, out AnimationPlayerComponent? animationPlayer))
+                animationPlayer.Stop(_jitterAnimationKey);
+
+            if (EntityManager.TryGetComponent(uid, out SpriteComponent? sprite))
+                sprite.Offset = Vector2.Zero;
+        }
+
+        private void OnAnimationCompleted(EntityUid uid, JitteringComponent jittering, AnimationCompletedEvent args)
+        {
+            if(args.Key != _jitterAnimationKey || jittering.EndTime <= GameTiming.CurTime)
+                return;
+
+            if(EntityManager.TryGetComponent(uid, out AnimationPlayerComponent? animationPlayer)
+            && EntityManager.TryGetComponent(uid, out ISpriteComponent? sprite))
+                animationPlayer.Play(GetAnimation(jittering, sprite), _jitterAnimationKey);
+        }
+
+        private Animation GetAnimation(JitteringComponent jittering, ISpriteComponent sprite)
+        {
+            var amplitude = MathF.Min(4f, jittering.Amplitude / 100f + 1f) / 10f;
+            var offset = new Vector2(_random.NextFloat(amplitude/4f, amplitude),
+                _random.NextFloat(amplitude / 4f, amplitude / 3f));
+
+            offset.X *= _random.Pick(_sign);
+            offset.Y *= _random.Pick(_sign);
+
+            if (Math.Sign(offset.X) == Math.Sign(jittering.LastJitter.X)
+                || Math.Sign(offset.Y) == Math.Sign(jittering.LastJitter.Y))
+            {
+                // If the sign is the same as last time on both axis we flip one randomly
+                // to avoid jitter staying in one quadrant too much.
+                if (_random.Prob(0.5f))
+                    offset.X *= -1;
+                else
+                    offset.Y *= -1;
+            }
+
+            // Animation length shouldn't be too high so we will cap it at 2 seconds...
+            var length = Math.Min((1f/jittering.Frequency), 2f);
+
+            jittering.LastJitter = offset;
+
+            return new Animation()
+            {
+                Length = TimeSpan.FromSeconds(length),
+                AnimationTracks =
+                {
+                    new AnimationTrackComponentProperty()
+                    {
+                        ComponentType = typeof(ISpriteComponent),
+                        Property = nameof(ISpriteComponent.Offset),
+                        KeyFrames =
+                        {
+                            new AnimationTrackProperty.KeyFrame(sprite.Offset, 0f),
+                            new AnimationTrackProperty.KeyFrame(offset, length),
+                        }
+                    }
+                }
+            };
+        }
+    }
+}