Implemented #2556: don't send tile NBT updates until the end of tick

this eliminates spam when tile spawn NBT changes a lot during a tick, for example the lines of a sign being updated.

closes #2556

src/pocketmine/level/Level.php

@@ -798,6 +798,12 @@ class Level implements ChunkManager, Metadatable{
 			if(!$tile->onUpdate()){
 				unset($this->updateTiles[$blockHash]);
 			}
+			if(!$tile->isClosed() and $tile instanceof Spawnable and $tile->isDirty()){
+				$this->clearChunkCache($tile->getFloorX() >> 4, $tile->getFloorZ() >> 4);
+				//TODO: merge this with block-updating (it'll send useless data if a full-chunk resend happens)
+				$this->broadcastPacketToViewers($tile, $tile->createSpawnPacket());
+				$tile->setDirty(false);
+			}
 		}
 		Timings::$tickTileEntityTimer->stopTiming();
 		$this->timings->tileEntityTick->stopTiming();
@@ -2587,10 +2593,6 @@ class Level implements ChunkManager, Metadatable{
 
 		$this->tiles[Level::blockHash($tile->x, $tile->y, $tile->z)] = $tile;
 		$tile->scheduleUpdate();
-		if($tile instanceof Spawnable){
-			$this->clearChunkCache($chunkX, $chunkZ);
-			$tile->spawnToAll();
-		}
 	}
 
 	/**

src/pocketmine/tile/Sign.php

@@ -88,17 +88,14 @@ class Sign extends Spawnable{
 	/**
 	 * @param int    $index 0-3
 	 * @param string $line
-	 * @param bool   $update
 	 */
-	public function setLine(int $index, string $line, bool $update = true) : void{
+	public function setLine(int $index, string $line) : void{
 		if($index < 0 or $index > 3){
 			throw new \InvalidArgumentException("Index must be in the range 0-3!");
 		}
 
 		$this->text[$index] = $line;
-		if($update){
+		$this->onChanged();
-			$this->onChanged();
-		}
 	}
 
 	/**

src/pocketmine/tile/Spawnable.php

@@ -33,6 +33,9 @@ use pocketmine\Player;
 abstract class Spawnable extends Tile{
 	/** @var string|null */
 	private $spawnCompoundCache = null;
+	/** @var bool */
+	private $dirty = true; //default dirty, until it's been spawned appropriately on the level
+
 	/** @var NetworkLittleEndianNBTStream|null */
 	private static $nbtWriter = null;
 
@@ -56,23 +59,30 @@ abstract class Spawnable extends Tile{
 		return true;
 	}
 
-	public function spawnToAll(){
-		if($this->closed){
-			return;
-		}
-
-		$this->level->broadcastPacketToViewers($this, $this->createSpawnPacket());
-	}
-
 	/**
-	 * Performs actions needed when the tile is modified, such as clearing caches and respawning the tile to players.
+	 * Flags the tile as modified, so that updates will be broadcasted at the next available opportunity.
-	 * WARNING: This MUST be called to clear spawn-compound and chunk caches when the tile's spawn compound has changed!
+	 * This MUST be called any time a change is made that players must be able to see.
 	 */
 	protected function onChanged() : void{
 		$this->spawnCompoundCache = null;
-		$this->spawnToAll();
+		$this->dirty = true;
+		$this->scheduleUpdate();
+	}
 
-		$this->level->clearChunkCache($this->getFloorX() >> 4, $this->getFloorZ() >> 4);
+	/**
+	 * Returns whether the tile needs to be respawned to viewers.
+	 *
+	 * @return bool
+	 */
+	public function isDirty() : bool{
+		return $this->dirty;
+	}
+
+	/**
+	 * @param bool $dirty
+	 */
+	public function setDirty(bool $dirty = true) : void{
+		$this->dirty = $dirty;
 	}
 
 	/**