Implement swimming/gliding including AABB recalculation (#4446)

- The following events have been added:
  - PlayerToggleGlideEvent
  - PlayerToggleSwimEvent
- The following API methods have been added:
  - Entity->getSize()
  - Living->isSwimming()
  - Living->setSwimming()
  - Living->isGliding()
  - Living->setSwimming()
  - Player->toggleSwim()
  - Player->toggleGlide()

src/entity/Entity.php

@@ -304,12 +304,8 @@ abstract class Entity{
 		if($value <= 0){
 			throw new \InvalidArgumentException("Scale must be greater than 0");
 		}
-		$this->size = $this->getInitialSizeInfo()->scale($value);
-
 		$this->scale = $value;
-
-		$this->recalculateBoundingBox();
-		$this->networkPropertiesDirty = true;
+		$this->setSize($this->getInitialSizeInfo()->scale($value));
 	}
 
 	public function getBoundingBox() : AxisAlignedBB{
@@ -329,6 +325,16 @@ abstract class Entity{
 		);
 	}
 
+	public function getSize() : EntitySizeInfo{
+		return $this->size;
+	}
+
+	protected function setSize(EntitySizeInfo $size) : void{
+		$this->size = $size;
+		$this->recalculateBoundingBox();
+		$this->networkPropertiesDirty = true;
+	}
+
 	public function isImmobile() : bool{
 		return $this->immobile;
 	}

src/entity/Living.php

@@ -116,6 +116,10 @@ abstract class Living extends Entity{
 	protected $sprinting = false;
 	/** @var bool */
 	protected $sneaking = false;
+	/** @var bool */
+	protected $gliding = false;
+	/** @var bool */
+	protected $swimming = false;
 
 	abstract public function getName() : string;
 
@@ -227,6 +231,37 @@ abstract class Living extends Entity{
 		}
 	}
 
+	public function isGliding() : bool{
+		return $this->gliding;
+	}
+
+	public function setGliding(bool $value = true) : void{
+		$this->gliding = $value;
+		$this->networkPropertiesDirty = true;
+		$this->recalculateSize();
+	}
+
+	public function isSwimming() : bool{
+		return $this->swimming;
+	}
+
+	public function setSwimming(bool $value = true) : void{
+		$this->swimming = $value;
+		$this->networkPropertiesDirty = true;
+		$this->recalculateSize();
+	}
+
+	private function recalculateSize() : void{
+		$size = $this->getInitialSizeInfo();
+		if($this->isSwimming() || $this->isGliding()){
+			$width = $size->getWidth();
+			//we don't actually know an appropriate eye height for a swimming mob, but 2/3 should be good enough.
+			$this->setSize((new EntitySizeInfo($width, $width, $width * 2 / 3))->scale($this->getScale()));
+		}else{
+			$this->setSize($size->scale($this->getScale()));
+		}
+	}
+
 	public function getMovementSpeed() : float{
 		return $this->moveSpeedAttr->getValue();
 	}
@@ -800,6 +835,8 @@ abstract class Living extends Entity{
 		$properties->setGenericFlag(EntityMetadataFlags::BREATHING, $this->breathing);
 		$properties->setGenericFlag(EntityMetadataFlags::SNEAKING, $this->sneaking);
 		$properties->setGenericFlag(EntityMetadataFlags::SPRINTING, $this->sprinting);
+		$properties->setGenericFlag(EntityMetadataFlags::GLIDING, $this->gliding);
+		$properties->setGenericFlag(EntityMetadataFlags::SWIMMING, $this->swimming);
 	}
 
 	protected function onDispose() : void{