From 43de87be0ddf6864be9ccf8febe8f9c00a46ab0e Mon Sep 17 00:00:00 2001
From: James Seibel <jeseibel@gondtc.com>
Date: Sat, 4 Mar 2023 21:15:50 -0600
Subject: [PATCH] Limit QuadTree concurrently loading LodRenderSections

---
 .../fullDatafile/FullDataFileHandler.java     |  2 +-
 .../seibel/lod/core/render/LodQuadTree.java   | 31 +++++++++++++++++--
 .../lod/core/render/LodRenderSection.java     |  1 +
 3 files changed, 31 insertions(+), 3 deletions(-)

diff --git a/core/src/main/java/com/seibel/lod/core/file/fullDatafile/FullDataFileHandler.java b/core/src/main/java/com/seibel/lod/core/file/fullDatafile/FullDataFileHandler.java
index 99a0b553a..e4198c72f 100644
--- a/core/src/main/java/com/seibel/lod/core/file/fullDatafile/FullDataFileHandler.java
+++ b/core/src/main/java/com/seibel/lod/core/file/fullDatafile/FullDataFileHandler.java
@@ -32,7 +32,7 @@ public class FullDataFileHandler implements IFullDataSourceProvider
 {
     // Note: Single main thread only for now. May make it multi-thread later, depending on the usage.
     private static final Logger LOGGER = DhLoggerBuilder.getLogger();
-    final ExecutorService fileReaderThread = ThreadUtil.makeThreadPool(4, "FileReaderThread");
+    final ExecutorService fileReaderThread = ThreadUtil.makeThreadPool(4, FullDataFileHandler.class.getSimpleName()+"Thread");
     final ConcurrentHashMap<DhSectionPos, FullDataMetaFile> files = new ConcurrentHashMap<>();
     final IDhLevel level;
     final File saveDir;
diff --git a/core/src/main/java/com/seibel/lod/core/render/LodQuadTree.java b/core/src/main/java/com/seibel/lod/core/render/LodQuadTree.java
index 6d5e9720f..c121095c9 100644
--- a/core/src/main/java/com/seibel/lod/core/render/LodQuadTree.java
+++ b/core/src/main/java/com/seibel/lod/core/render/LodQuadTree.java
@@ -14,6 +14,8 @@ import com.seibel.lod.core.util.MathUtil;
 import com.seibel.lod.core.util.gridList.MovableGridRingList;
 import org.apache.logging.log4j.Logger;
 
+import java.util.concurrent.CompletableFuture;
+
 /**
  * This quadTree structure is our core data structure and holds
  * all rendering data. <br><br>
@@ -54,7 +56,15 @@ public class LodQuadTree implements AutoCloseable
     public final int blockRenderDistance;
     private final ILodRenderSourceProvider renderSourceProvider;
 	
-    private final IDhClientLevel level; //FIXME: Proper hierarchy to remove this reference!
+	/** How many {@link LodRenderSection}'s are currently loading */
+	private int numberOfRenderSectionsLoading = 0;
+	/** 
+	 * Indicates how many {@link LodRenderSection}'s can load concurrently. <br>
+	 * Prevents large number of {@link ILodRenderSourceProvider} tasks from building up when initially loading. 
+	 */
+	private static final int MAX_NUMBER_OF_LOADING_RENDER_SECTIONS = 2;
+	
+	private final IDhClientLevel level; //FIXME: Proper hierarchy to remove this reference!
 	
 	
 	
@@ -596,7 +606,24 @@ public class LodQuadTree implements AutoCloseable
 					}
 					else if (section.childCount == 0)
 					{
-						section.loadRenderSourceAndEnableRendering();
+						// limit how many render sections can be loading at a time
+						if (!section.isRenderingEnabled() && this.numberOfRenderSectionsLoading < MAX_NUMBER_OF_LOADING_RENDER_SECTIONS)
+						{
+							section.loadRenderSourceAndEnableRendering();
+							
+							this.numberOfRenderSectionsLoading++;
+							
+							CompletableFuture<ColumnRenderSource> future = section.getRenderSourceLoadingFuture();
+							if (future != null)
+							{
+								future.whenComplete((renderSource, ex) -> this.numberOfRenderSectionsLoading-- );
+							}
+							else
+							{
+								// the future will be null if the section was already loaded
+								this.numberOfRenderSectionsLoading--;
+							}
+						}
 					}
 					
 					
diff --git a/core/src/main/java/com/seibel/lod/core/render/LodRenderSection.java b/core/src/main/java/com/seibel/lod/core/render/LodRenderSection.java
index 8fd5f9e7d..fb1e3cf46 100644
--- a/core/src/main/java/com/seibel/lod/core/render/LodRenderSection.java
+++ b/core/src/main/java/com/seibel/lod/core/render/LodRenderSection.java
@@ -148,6 +148,7 @@ public class LodRenderSection
     public boolean isOutdated() { return this.renderSource != null && !this.renderSource.isValid(); }
 	
     public ColumnRenderSource getRenderSource() { return this.renderSource; }
+    public CompletableFuture<ColumnRenderSource> getRenderSourceLoadingFuture() { return this.loadFuture; }
 	
 	
 	//==============//