QTaskBuilder::spawn: add an overload that doesn't return a future object

Fixes: QTBUG-83175
Change-Id: Idf85e47a2732742884272200d5c753805eaa640b
Reviewed-by: Sona Kurazyan <sona.kurazyan@qt.io>

4 files changed, 40 insertions, 0 deletions

diff --git a/src/concurrent/doc/snippets/code/src_concurrent_qtconcurrenttask.cpp b/src/concurrent/doc/snippets/code/src_concurrent_qtconcurrenttask.cpp
index bec45ba3bf..b067b49e7e 100644
--- a/src/concurrent/doc/snippets/code/src_concurrent_qtconcurrenttask.cpp
+++ b/src/concurrent/doc/snippets/code/src_concurrent_qtconcurrenttask.cpp
@@ -125,3 +125,7 @@ QtConcurrent::task([]{ return 42; }).onThreadPool(pool).spawn();
 //! [10]
 QtConcurrent::task([]{ return 42; }).withPriority(10).spawn();
 //! [10]
+
+//! [11]
+QtConcurrent::task([]{ qDebug("Hello, world!"); }).spawn(FutureResult::Ignore);
+//! [11]
diff --git a/src/concurrent/qtaskbuilder.h b/src/concurrent/qtaskbuilder.h
index 5fc2bccfb5..074dad1c6b 100644
--- a/src/concurrent/qtaskbuilder.h
+++ b/src/concurrent/qtaskbuilder.h
@@ -52,6 +52,8 @@ QT_BEGIN_NAMESPACE
 
 namespace QtConcurrent {
 
+enum class FutureResult { Ignore };
+
 using InvokeResultType = int;
 
 template <class Task, class ...Args>
@@ -61,6 +63,8 @@ public:
     [[nodiscard]]
     QFuture<InvokeResultType> spawn();
 
+    void spawn(FutureResult);
+
     template <class ...ExtraArgs>
     [[nodiscard]]
     QTaskBuilder<Task, ExtraArgs...> withArguments(ExtraArgs &&...args);
@@ -78,6 +82,8 @@ public:
 
 namespace QtConcurrent {
 
+enum class FutureResult { Ignore };
+
 template <class Task, class ...Args>
 class QTaskBuilder
 {
@@ -89,6 +95,12 @@ public:
                    ->start(startParameters);
     }
 
+    void spawn(FutureResult)
+    {
+        (new StoredFunctionCall<Task, Args...>(std::move(taskWithArgs)))
+            ->start(startParameters);
+    }
+
     template <class ...ExtraArgs>
     [[nodiscard]]
     constexpr auto withArguments(ExtraArgs &&...args)
diff --git a/src/concurrent/qtaskbuilder.qdoc b/src/concurrent/qtaskbuilder.qdoc
index 8352cae17a..1340307806 100644
--- a/src/concurrent/qtaskbuilder.qdoc
+++ b/src/concurrent/qtaskbuilder.qdoc
@@ -45,6 +45,13 @@
 */
 
 /*!
+    \fn template <class Task, class ...Args> void QtConcurrent::QTaskBuilder<Task, Args...>::spawn(QtConcurrent::FutureResult)
+
+    Runs the task in a separate thread. This is a non-blocking call.
+    The task might not start immediately.
+*/
+
+/*!
     \fn template <class Task, class ...Args> template <class ...ExtraArgs> [[nodiscard]] QTaskBuilder<Task, ExtraArgs...> QtConcurrent::QTaskBuilder<Task, Args...>::withArguments(ExtraArgs &&...args)
 
     Sets the arguments \a args the task will be invoked with. The code is ill-formed
@@ -80,3 +87,15 @@
     The real implementation also contains a compile-time check for
     whether the task can be invoked with the specified arguments or not.
 */
+
+/*!
+    \enum QtConcurrent::FutureResult
+
+    This enum type is used to invoke a special overload of
+    QtConcurrent::QTaskBuilder::spawn(QtConcurrent::FutureResult)
+    that doesn't return a future object.
+
+    \value Ignore
+           An auxiliary tag which introduced to improve code
+           readability.
+*/
diff --git a/src/concurrent/qtconcurrenttask.qdoc b/src/concurrent/qtconcurrenttask.qdoc
index e25e485bd1..9000b424fe 100644
--- a/src/concurrent/qtconcurrenttask.qdoc
+++ b/src/concurrent/qtconcurrenttask.qdoc
@@ -143,6 +143,11 @@
     You can set the priority for a task:
 
     \snippet code/src_concurrent_qtconcurrenttask.cpp 10
+
+    If you don't need a future object, you can call
+    QtConcurrent::QTaskBuilder::spawn(QtConcurrent::FutureResult::Ignore):
+
+    \snippet code/src_concurrent_qtconcurrenttask.cpp 11
 */
 
 /*!