godot/doc/classes/Thread.xml

<?xml version="1.0" encoding="UTF-8" ?>
<class name="Thread" inherits="Reference" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:noNamespaceSchemaLocation="../class.xsd">
	<brief_description>
		A unit of execution in a process.
	</brief_description>
	<description>
		A unit of execution in a process. Can run methods on [Object]s simultaneously. The use of synchronization via [Mutex] or [Semaphore] is advised if working with shared objects.
		[b]Note:[/b] Breakpoints won't break on code if it's running in a thread. This is a current limitation of the GDScript debugger.
		[b]Warning:[/b]
		To guarantee that the operating system is able to perform proper cleanup (no crashes, no deadlocks), these conditions must be met by the time a [Thread]'s reference count reaches zero and therefore it is destroyed:
		- It must not have any [Mutex] objects locked.
		- It must not be waiting on any [Semaphore] objects.
		- [method wait_to_finish] should have been called on it.
	</description>
	<tutorials>
		<link title="Using multiple threads">$DOCS_URL/tutorials/performance/threads/using_multiple_threads.html</link>
		<link title="Thread-safe APIs">$DOCS_URL/tutorials/performance/threads/thread_safe_apis.html</link>
		<link title="3D Voxel Demo">https://godotengine.org/asset-library/asset/676</link>
	</tutorials>
	<methods>
		<method name="get_id" qualifiers="const">
			<return type="String" />
			<description>
				Returns the current [Thread]'s ID, uniquely identifying it among all threads. If the [Thread] is not running this returns an empty string.
			</description>
		</method>
		<method name="is_active" qualifiers="const">
			<return type="bool" />
			<description>
				Returns [code]true[/code] if this [Thread] has been started. Once started, this will return [code]true[/code] until it is joined using [method wait_to_finish]. For checking if a [Thread] is still executing its task, use [method is_alive].
			</description>
		</method>
		<method name="is_alive" qualifiers="const">
			<return type="bool" />
			<description>
				Returns [code]true[/code] if this [Thread] is currently running. This is useful for determining if [method wait_to_finish] can be called without blocking the calling thread.
				To check if a [Thread] is joinable, use [method is_active].
			</description>
		</method>
		<method name="start">
			<return type="int" enum="Error" />
			<argument index="0" name="instance" type="Object" />
			<argument index="1" name="method" type="String" />
			<argument index="2" name="userdata" type="Variant" default="null" />
			<argument index="3" name="priority" type="int" enum="Thread.Priority" default="1" />
			<description>
				Starts a new [Thread] that runs [code]method[/code] on object [code]instance[/code] with [code]userdata[/code] passed as an argument. Even if no userdata is passed, [code]method[/code] must accept one argument and it will be null. The [code]priority[/code] of the [Thread] can be changed by passing a value from the [enum Priority] enum.
				Returns [constant OK] on success, or [constant ERR_CANT_CREATE] on failure.
			</description>
		</method>
		<method name="wait_to_finish">
			<return type="Variant" />
			<description>
				Joins the [Thread] and waits for it to finish. Returns the output of the method passed to [method start].
				Should either be used when you want to retrieve the value returned from the method called by the [Thread] or before freeing the instance that contains the [Thread].
				To determine if this can be called without blocking the calling thread, check if [method is_alive] is [code]false[/code].
				[b]Note:[/b] After the [Thread] finishes joining it will be disposed. If you want to use it again you will have to create a new instance of it.
			</description>
		</method>
	</methods>
	<constants>
		<constant name="PRIORITY_LOW" value="0" enum="Priority">
			A thread running with lower priority than normally.
		</constant>
		<constant name="PRIORITY_NORMAL" value="1" enum="Priority">
			A thread with a standard priority.
		</constant>
		<constant name="PRIORITY_HIGH" value="2" enum="Priority">
			A thread running with higher priority than normally.
		</constant>
	</constants>
</class>