1 files changed, 135 insertions, 0 deletions
diff --git a/src/concurrent/qtaskbuilder.h b/src/concurrent/qtaskbuilder.h
new file mode 100644
index 0000000000..95ab8021e7
--- /dev/null
+++ b/src/concurrent/qtaskbuilder.h
@@ -0,0 +1,135 @@
+// Copyright (C) 2020 The Qt Company Ltd.
+// SPDX-License-Identifier: LicenseRef-Qt-Commercial OR LGPL-3.0-only OR GPL-2.0-only OR GPL-3.0-only
+
+#ifndef QTBASE_QTTASKBUILDER_H
+#define QTBASE_QTTASKBUILDER_H
+
+#if !defined(QT_NO_CONCURRENT) || defined(Q_QDOC)
+
+#include <QtConcurrent/qtconcurrentstoredfunctioncall.h>
+
+QT_BEGIN_NAMESPACE
+
+#ifdef Q_QDOC
+
+namespace QtConcurrent {
+
+enum class FutureResult { Ignore };
+
+using InvokeResultType = int;
+
+template <class Task, class ...Args>
+class QTaskBuilder
+{
+public:
+    [[nodiscard]]
+    QFuture<InvokeResultType> spawn();
+
+    void spawn(FutureResult);
+
+    template <class ...ExtraArgs>
+    [[nodiscard]]
+    QTaskBuilder<Task, ExtraArgs...> withArguments(ExtraArgs &&...args);
+
+    [[nodiscard]]
+    QTaskBuilder<Task, Args...> &onThreadPool(QThreadPool &newThreadPool);
+
+    [[nodiscard]]
+    QTaskBuilder<Task, Args...> &withPriority(int newPriority);
+};
+
+} // namespace QtConcurrent
+
+#else
+
+namespace QtConcurrent {
+
+enum class FutureResult { Ignore };
+
+template <class Task, class ...Args>
+class QTaskBuilder
+{
+public:
+    [[nodiscard]]
+    auto spawn()
+    {
+        return TaskResolver<std::decay_t<Task>, std::decay_t<Args>...>::run(
+                    std::move(taskWithArgs), startParameters);
+    }
+
+    // We don't want to run with promise when we don't return a QFuture
+    void spawn(FutureResult)
+    {
+        (new StoredFunctionCall<Task, Args...>(std::move(taskWithArgs)))
+            ->start(startParameters);
+    }
+
+    template <class ...ExtraArgs>
+    [[nodiscard]]
+    constexpr auto withArguments(ExtraArgs &&...args)
+    {
+        static_assert(std::tuple_size_v<TaskWithArgs> == 1,
+                      "This function cannot be invoked if "
+                      "arguments have already been passed.");
+
+        static_assert(sizeof...(ExtraArgs) >= 1,
+                      "One or more arguments must be passed.");
+
+        // We have to re-create a builder, because the type has changed
+        return QTaskBuilder<Task, ExtraArgs...>(
+                   startParameters,
+                   std::get<0>(std::move(taskWithArgs)),
+                   std::forward<ExtraArgs>(args)...
+               );
+    }
+
+    [[nodiscard]]
+    constexpr auto &onThreadPool(QThreadPool &newThreadPool)
+    {
+        startParameters.threadPool = &newThreadPool;
+        return *this;
+    }
+
+    [[nodiscard]]
+    constexpr auto &withPriority(int newPriority)
+    {
+        startParameters.priority = newPriority;
+        return *this;
+    }
+
+protected: // Methods
+    constexpr explicit QTaskBuilder(Task &&task, Args &&...arguments)
+        : taskWithArgs{std::forward<Task>(task), std::forward<Args>(arguments)...}
+    {}
+
+    constexpr QTaskBuilder(
+        const TaskStartParameters &parameters, Task &&task, Args &&...arguments)
+        : taskWithArgs{std::forward<Task>(task), std::forward<Args>(arguments)...}
+        , startParameters{parameters}
+    {}
+
+private: // Methods
+    // Required for creating a builder from "task" function
+    template <class T>
+    friend constexpr auto task(T &&t);
+
+    // Required for creating a new builder from "withArguments" function
+    template <class T, class ...A>
+    friend class QTaskBuilder;
+
+private: // Data
+    using TaskWithArgs = DecayedTuple<Task, Args...>;
+
+    TaskWithArgs taskWithArgs;
+    TaskStartParameters startParameters;
+};
+
+} // namespace QtConcurrent
+
+#endif // Q_QDOC
+
+QT_END_NAMESPACE
+
+#endif // !defined(QT_NO_CONCURRENT)
+
+#endif //QTBASE_QTTASKBUILDER_H