Cam tweening working! UI buggy af. To fix.

source/funkin/play/PlayState.hx

@@ -219,6 +219,12 @@ class PlayState extends MusicBeatSubState
    */
   public var cameraFollowPoint:FlxObject;
 
+  /**
+   * An FlxTween that tweens the camera to the follow point.
+   * Only used when tweening the camera manually, rather than tweening via follow.
+   */
+  public var cameraFollowTween:FlxTween;
+
   /**
    * The camera follow point from the last stage.
    * Used to persist the position of the `cameraFollowPosition` between levels.
@@ -2847,15 +2853,51 @@ class PlayState extends MusicBeatSubState
   /**
    * Resets the camera's zoom level and focus point.
    */
-  public function resetCamera():Void
+  public function resetCamera(?resetZoom:Bool = true, ?cancelFollowTween:Bool = true):Void
   {
+    // Cancel the follow tween if it's active.
+    if (cancelFollowTween && cameraFollowTween != null)
+    {
+      cameraFollowTween.cancel();
+    }
+
     FlxG.camera.follow(cameraFollowPoint, LOCKON, 0.04);
     FlxG.camera.targetOffset.set();
-    FlxG.camera.zoom = defaultCameraZoom;
+
+    if (resetZoom)
+    {
+      FlxG.camera.zoom = defaultCameraZoom;
+    }
+
     // Snap the camera to the follow point immediately.
     FlxG.camera.focusOn(cameraFollowPoint.getPosition());
   }
 
+  /**
+   * Disables camera following and tweens the camera to the follow point manually.
+   */
+  public function tweenCamera(?duration:Float, ?ease:Null<Float->Float>):Void
+  {
+    // Cancel the current tween if it's active.
+    if (cameraFollowTween != null)
+    {
+      cameraFollowTween.cancel();
+    }
+
+    // Disable camera following for the duration of the tween.
+    FlxG.camera.target = null;
+
+    // Follow tween! Caching it so we can cancel it later if needed.
+    var followPos:FlxPoint = cameraFollowPoint.getPosition() - FlxPoint.weak(FlxG.camera.width * 0.5, FlxG.camera.height * 0.5);
+    cameraFollowTween = FlxTween.tween(FlxG.camera.scroll, {x: followPos.x, y: followPos.y}, duration,
+      {
+        ease: ease,
+        onComplete: function(_) {
+          resetCamera(false, false); // Re-enable camera following when the tween is complete.
+        }
+      });
+  }
+
   #if (debug || FORCE_DEBUG_VERSION)
   /**
    * Jumps forward or backward a number of sections in the song.

source/funkin/play/event/FocusCameraSongEvent.hx

@@ -1,5 +1,6 @@
 package funkin.play.event;
 
+import flixel.tweens.FlxEase;
 // Data from the chart
 import funkin.data.song.SongData;
 import funkin.data.song.SongData.SongEventData;
@@ -66,6 +67,13 @@ class FocusCameraSongEvent extends SongEvent
 
     if (char == null) char = cast data.value;
 
+    var useTween:Null<Bool> = data.getBool('useTween');
+    if (useTween == null) useTween = false;
+    var duration:Null<Float> = data.getFloat('duration');
+    if (duration == null) duration = 4.0;
+    var ease:Null<String> = data.getString('ease');
+    if (ease == null) ease = 'linear';
+
     switch (char)
     {
       case -1: // Position
@@ -114,6 +122,20 @@ class FocusCameraSongEvent extends SongEvent
       default:
         trace('Unknown camera focus: ' + data);
     }
+
+    if (useTween) // always ends up false??
+    {
+      var durSeconds = Conductor.instance.stepLengthMs * duration / 1000;
+
+      var easeFunction:Null<Float->Float> = Reflect.field(FlxEase, ease);
+      if (easeFunction == null)
+      {
+        trace('Invalid ease function: $ease');
+        return;
+      }
+
+      PlayState.instance.tweenCamera(durSeconds, easeFunction);
+    }
   }
 
   public override function getTitle():String
@@ -155,6 +177,51 @@ class FocusCameraSongEvent extends SongEvent
         step: 10.0,
         type: SongEventFieldType.FLOAT,
         units: "px"
+      },
+      {
+        name: 'useTween',
+        title: 'Use Tween',
+        type: SongEventFieldType.BOOL,
+        defaultValue: false
+      },
+      {
+        name: 'duration',
+        title: 'Duration',
+        defaultValue: 4.0,
+        step: 0.5,
+        type: SongEventFieldType.FLOAT,
+        units: 'steps'
+      },
+      {
+        name: 'ease',
+        title: 'Easing Type',
+        defaultValue: 'linear',
+        type: SongEventFieldType.ENUM,
+        keys: [
+          'Linear' => 'linear',
+          'Instant' => 'INSTANT',
+          'Quad In' => 'quadIn',
+          'Quad Out' => 'quadOut',
+          'Quad In/Out' => 'quadInOut',
+          'Cube In' => 'cubeIn',
+          'Cube Out' => 'cubeOut',
+          'Cube In/Out' => 'cubeInOut',
+          'Quart In' => 'quartIn',
+          'Quart Out' => 'quartOut',
+          'Quart In/Out' => 'quartInOut',
+          'Quint In' => 'quintIn',
+          'Quint Out' => 'quintOut',
+          'Quint In/Out' => 'quintInOut',
+          'Smooth Step In' => 'smoothStepIn',
+          'Smooth Step Out' => 'smoothStepOut',
+          'Smooth Step In/Out' => 'smoothStepInOut',
+          'Sine In' => 'sineIn',
+          'Sine Out' => 'sineOut',
+          'Sine In/Out' => 'sineInOut',
+          'Elastic In' => 'elasticIn',
+          'Elastic Out' => 'elasticOut',
+          'Elastic In/Out' => 'elasticInOut',
+        ]
       }
     ]);
   }