From 1ca23c514f978cd69d0f950cd15b75d099a4c94b Mon Sep 17 00:00:00 2001
From: Jozufozu <jozsefaug@gmail.com>
Date: Thu, 22 Jul 2021 14:07:02 -0700
Subject: [PATCH] Instance stealing

---
 .../backend/instancing/InstanceData.java      |  2 +-
 .../backend/instancing/Instancer.java         | 24 ++++++++++++++-----
 2 files changed, 19 insertions(+), 7 deletions(-)

diff --git a/src/main/java/com/jozufozu/flywheel/backend/instancing/InstanceData.java b/src/main/java/com/jozufozu/flywheel/backend/instancing/InstanceData.java
index cfd7b5c8f..21eaed753 100644
--- a/src/main/java/com/jozufozu/flywheel/backend/instancing/InstanceData.java
+++ b/src/main/java/com/jozufozu/flywheel/backend/instancing/InstanceData.java
@@ -4,7 +4,7 @@ import com.jozufozu.flywheel.backend.gl.buffer.MappedBuffer;
 
 public abstract class InstanceData {
 
-	protected final Instancer<?> owner;
+	Instancer<?> owner;
 
 	boolean dirty;
 	boolean removed;
diff --git a/src/main/java/com/jozufozu/flywheel/backend/instancing/Instancer.java b/src/main/java/com/jozufozu/flywheel/backend/instancing/Instancer.java
index e18c6cefc..cbfc9373c 100644
--- a/src/main/java/com/jozufozu/flywheel/backend/instancing/Instancer.java
+++ b/src/main/java/com/jozufozu/flywheel/backend/instancing/Instancer.java
@@ -71,12 +71,14 @@ public class Instancer<D extends InstanceData> {
 	}
 
 	public D createInstance() {
-		D instanceData = factory.create(this);
-		instanceData.dirty = true;
-		anyToUpdate = true;
-		data.add(instanceData);
+		return _add(factory.create(this));
+	}
 
-		return instanceData;
+	public void stealInstance(D inOther) {
+		if (inOther.owner == this) return;
+
+		inOther.owner.anyToRemove = true;
+		_add(inOther);
 	}
 
 	public boolean empty() {
@@ -105,6 +107,16 @@ public class Instancer<D extends InstanceData> {
 		vao.delete();
 	}
 
+	private D _add(D instanceData) {
+		instanceData.owner = this;
+
+		instanceData.dirty = true;
+		anyToUpdate = true;
+		data.add(instanceData);
+
+		return instanceData;
+	}
+
 	protected void renderSetup() {
 		if (anyToRemove) {
 			removeDeletedInstances();
@@ -215,7 +227,7 @@ public class Instancer<D extends InstanceData> {
 		final BitSet removeSet = new BitSet(oldSize);
 		for (int i = 0; i < oldSize; i++) {
 			final D element = this.data.get(i);
-			if (element.removed) {
+			if (element.removed || element.owner != this) {
 				removeSet.set(i);
 				removeCount++;
 			}