Throwing item scaling animation + recoil (#24724)

Content.Client/Throwing/ThrownItemVisualizerSystem.cs

@@ -0,0 +1,87 @@
+using Content.Shared.Throwing;
+using Robust.Client.Animations;
+using Robust.Client.GameObjects;
+using Robust.Shared.Animations;
+
+namespace Content.Client.Throwing;
+
+/// <summary>
+///     Handles animating thrown items.
+/// </summary>
+public sealed class ThrownItemVisualizerSystem : EntitySystem
+{
+    [Dependency] private readonly AnimationPlayerSystem _anim = default!;
+
+    private const string AnimationKey = "thrown-item";
+
+    public override void Initialize()
+    {
+        base.Initialize();
+
+        SubscribeLocalEvent<ThrownItemComponent, AfterAutoHandleStateEvent>(OnAutoHandleState);
+        SubscribeLocalEvent<ThrownItemComponent, ComponentShutdown>(OnShutdown);
+    }
+
+    private void OnAutoHandleState(EntityUid uid, ThrownItemComponent component, ref AfterAutoHandleStateEvent args)
+    {
+        if (!TryComp<SpriteComponent>(uid, out var sprite))
+            return;
+
+        var animationPlayer = EnsureComp<AnimationPlayerComponent>(uid);
+
+        if (_anim.HasRunningAnimation(uid, animationPlayer, AnimationKey))
+            return;
+
+        var anim = GetAnimation((uid, component, sprite));
+        if (anim == null)
+            return;
+
+        component.OriginalScale = sprite.Scale;
+        _anim.Play((uid, animationPlayer), anim, AnimationKey);
+    }
+
+    private void OnShutdown(EntityUid uid, ThrownItemComponent component, ComponentShutdown args)
+    {
+        if (!_anim.HasRunningAnimation(uid, AnimationKey))
+            return;
+
+        if (TryComp<SpriteComponent>(uid, out var sprite) && component.OriginalScale != null)
+            sprite.Scale = component.OriginalScale.Value;
+
+        _anim.Stop(uid, AnimationKey);
+    }
+
+    private static Animation? GetAnimation(Entity<ThrownItemComponent, SpriteComponent> ent)
+    {
+        if (ent.Comp1.LandTime - ent.Comp1.ThrownTime is not { } length)
+            return null;
+
+        if (length <= TimeSpan.Zero)
+            return null;
+
+        length += TimeSpan.FromSeconds(ThrowingSystem.FlyTime);
+        var scale = ent.Comp2.Scale;
+        var lenFloat = (float) length.TotalSeconds;
+
+        // TODO use like actual easings here
+        return new Animation
+        {
+            Length = length,
+            AnimationTracks =
+            {
+                new AnimationTrackComponentProperty
+                {
+                    ComponentType = typeof(SpriteComponent),
+                    Property = nameof(SpriteComponent.Scale),
+                    KeyFrames =
+                    {
+                        new AnimationTrackProperty.KeyFrame(scale, 0.0f),
+                        new AnimationTrackProperty.KeyFrame(scale * 1.4f, lenFloat * 0.25f),
+                        new AnimationTrackProperty.KeyFrame(scale, lenFloat * 0.75f)
+                    },
+                    InterpolationMode = AnimationInterpolationMode.Linear
+                }
+            }
+        };
+    }
+}