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[3.x] [core_bind] Add Thread::is_alive #53490

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Oct 12, 2021
Merged

[3.x] [core_bind] Add Thread::is_alive #53490

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20 changes: 14 additions & 6 deletions core/bind/core_bind.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -2680,12 +2680,15 @@ void _Thread::_start_func(void *ud) {
}
}

t->running.clear();
ERR_FAIL_MSG("Could not call function '" + t->target_method.operator String() + "' to start thread " + t->get_id() + ": " + reason + ".");
}

t->running.clear();
}

Error _Thread::start(Object *p_instance, const StringName &p_method, const Variant &p_userdata, Priority p_priority) {
ERR_FAIL_COND_V_MSG(active.is_set(), ERR_ALREADY_IN_USE, "Thread already started.");
ERR_FAIL_COND_V_MSG(is_active(), ERR_ALREADY_IN_USE, "Thread already started.");
ERR_FAIL_COND_V(!p_instance, ERR_INVALID_PARAMETER);
ERR_FAIL_COND_V(p_method == StringName(), ERR_INVALID_PARAMETER);
ERR_FAIL_INDEX_V(p_priority, PRIORITY_MAX, ERR_INVALID_PARAMETER);
Expand All @@ -2694,7 +2697,7 @@ Error _Thread::start(Object *p_instance, const StringName &p_method, const Varia
target_method = p_method;
target_instance_id = p_instance->get_instance_id();
userdata = p_userdata;
active.set();
running.set();

Ref<_Thread> *ud = memnew(Ref<_Thread>(this));

Expand All @@ -2710,16 +2713,20 @@ String _Thread::get_id() const {
}

bool _Thread::is_active() const {
return active.is_set();
return thread.is_started();
}

bool _Thread::is_alive() const {
return running.is_set();
}

Variant _Thread::wait_to_finish() {
ERR_FAIL_COND_V_MSG(!active.is_set(), Variant(), "Thread must be active to wait for its completion.");
ERR_FAIL_COND_V_MSG(!is_active(), Variant(), "Thread must have been started to wait for its completion.");
thread.wait_to_finish();
Variant r = ret;
target_method = StringName();
target_instance_id = ObjectID();
userdata = Variant();
active.clear();

return r;
}
Expand All @@ -2728,6 +2735,7 @@ void _Thread::_bind_methods() {
ClassDB::bind_method(D_METHOD("start", "instance", "method", "userdata", "priority"), &_Thread::start, DEFVAL(Variant()), DEFVAL(PRIORITY_NORMAL));
ClassDB::bind_method(D_METHOD("get_id"), &_Thread::get_id);
ClassDB::bind_method(D_METHOD("is_active"), &_Thread::is_active);
ClassDB::bind_method(D_METHOD("is_alive"), &_Thread::is_alive);
ClassDB::bind_method(D_METHOD("wait_to_finish"), &_Thread::wait_to_finish);

BIND_ENUM_CONSTANT(PRIORITY_LOW);
Expand All @@ -2739,7 +2747,7 @@ _Thread::_Thread() {
}

_Thread::~_Thread() {
ERR_FAIL_COND_MSG(active.is_set(), "Reference to a Thread object was lost while the thread is still running...");
ERR_FAIL_COND_MSG(is_active(), "Reference to a Thread object was lost while the thread is still running...");
}

/////////////////////////////////////
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3 changes: 2 additions & 1 deletion core/bind/core_bind.h
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Original file line number Diff line number Diff line change
Expand Up @@ -683,7 +683,7 @@ class _Thread : public Reference {
protected:
Variant ret;
Variant userdata;
SafeFlag active;
SafeFlag running;
ObjectID target_instance_id;
StringName target_method;
Thread thread;
Expand All @@ -702,6 +702,7 @@ class _Thread : public Reference {
Error start(Object *p_instance, const StringName &p_method, const Variant &p_userdata = Variant(), Priority p_priority = PRIORITY_NORMAL);
String get_id() const;
bool is_active() const;
bool is_alive() const;
Variant wait_to_finish();

_Thread();
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12 changes: 10 additions & 2 deletions doc/classes/Thread.xml
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Expand Up @@ -22,7 +22,14 @@
<method name="is_active" qualifiers="const">
<return type="bool" />
<description>
Returns [code]true[/code] if this [Thread] is currently active. An active [Thread] cannot start work on a new method but can be joined with [method wait_to_finish].
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">
Expand All @@ -39,8 +46,9 @@
<method name="wait_to_finish">
<return type="Variant" />
<description>
Joins the [Thread] and waits for it to finish. Returns what the method called returned.
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>
Expand Down