Add a constructor for QRunnable from anonymous functions

This makes it easier to create one without having to create
a derivative class. The patch also adds a path to avoid using
QRunnable directly in QThreadPool.

Change-Id: I9caa7dabb6f641b547d4771c863aa6ab7f01b704
Reviewed-by: Thiago Macieira <thiago.macieira@intel.com>
Reviewed-by: Sona Kurazyan <sona.kurazyan@qt.io>

4 files changed, 66 insertions, 0 deletions

diff --git a/src/corelib/thread/qrunnable.cpp b/src/corelib/thread/qrunnable.cpp
index bd0a32b53d..58a764d407 100644
--- a/src/corelib/thread/qrunnable.cpp
+++ b/src/corelib/thread/qrunnable.cpp
@@ -114,4 +114,31 @@ QRunnable::~QRunnable()
     \sa autoDelete(), QThreadPool
 */
 
+class FunctionRunnable : public QRunnable
+{
+    std::function<void()> m_functor;
+public:
+    FunctionRunnable(std::function<void()> functor) : m_functor(std::move(functor))
+    {
+    }
+    void run() override
+    {
+        m_functor();
+    }
+};
+
+/*!
+    \since 5.15
+
+    Creates a QRunnable that calls \a fun in run().
+
+    Auto-deletion is enabled by default.
+
+    \sa run(), autoDelete()
+*/
+QRunnable *QRunnable::create(std::function<void()> fun)
+{
+    return new FunctionRunnable(std::move(fun));
+}
+
 QT_END_NAMESPACE
diff --git a/src/corelib/thread/qrunnable.h b/src/corelib/thread/qrunnable.h
index b8e842118c..c13aa3fa8c 100644
--- a/src/corelib/thread/qrunnable.h
+++ b/src/corelib/thread/qrunnable.h
@@ -41,6 +41,7 @@
 #define QRUNNABLE_H
 
 #include <QtCore/qglobal.h>
+#include <functional>
 
 QT_BEGIN_NAMESPACE
 
@@ -59,6 +60,7 @@ public:
 
     QRunnable() : ref(0) { }
     virtual ~QRunnable();
+    static QRunnable *create(std::function<void()> fun);
 
     bool autoDelete() const { return ref != -1; }
     void setAutoDelete(bool _autoDelete) { ref = _autoDelete ? 0 : -1; }
diff --git a/src/corelib/thread/qthreadpool.cpp b/src/corelib/thread/qthreadpool.cpp
index 5f23a78c8a..d1875a69a9 100644
--- a/src/corelib/thread/qthreadpool.cpp
+++ b/src/corelib/thread/qthreadpool.cpp
@@ -512,6 +512,22 @@ void QThreadPool::start(QRunnable *runnable, int priority)
 }
 
 /*!
+    \overload
+    \since 5.15
+
+    Reserves a thread and uses it to run \a fun, unless this thread will
+    make the current thread count exceed maxThreadCount().  In that case,
+    \a fun is added to a run queue instead. The \a priority argument can
+    be used to control the run queue's order of execution.
+*/
+void QThreadPool::start(std::function<void()> fun, int priority)
+{
+    if (!fun)
+        return;
+    start(QRunnable::create(std::move(fun)), priority);
+}
+
+/*!
     Attempts to reserve a thread to run \a runnable.
 
     If no threads are available at the time of calling, then this function
@@ -542,6 +558,22 @@ bool QThreadPool::tryStart(QRunnable *runnable)
     return d->tryStart(runnable);
 }
 
+/*!
+    \overload
+    \since 5.15
+    Attempts to reserve a thread to run \a fun.
+
+    If no threads are available at the time of calling, then this function
+    does nothing and returns \c false.  Otherwise, \a fun is run immediately
+    using one available thread and this function returns \c true.
+*/
+bool QThreadPool::tryStart(std::function<void()> fun)
+{
+    if (!fun)
+        return false;
+    return tryStart(QRunnable::create(std::move(fun)));
+}
+
 /*! \property QThreadPool::expiryTimeout
 
     Threads that are unused for \a expiryTimeout milliseconds are considered
diff --git a/src/corelib/thread/qthreadpool.h b/src/corelib/thread/qthreadpool.h
index cd27b7c08a..2eede44eca 100644
--- a/src/corelib/thread/qthreadpool.h
+++ b/src/corelib/thread/qthreadpool.h
@@ -45,6 +45,8 @@
 #include <QtCore/qthread.h>
 #include <QtCore/qrunnable.h>
 
+#include <functional>
+
 QT_REQUIRE_CONFIG(thread);
 
 QT_BEGIN_NAMESPACE
@@ -70,6 +72,9 @@ public:
     void start(QRunnable *runnable, int priority = 0);
     bool tryStart(QRunnable *runnable);
 
+    void start(std::function<void()> fun, int priority = 0);
+    bool tryStart(std::function<void()> fun);
+
     int expiryTimeout() const;
     void setExpiryTimeout(int expiryTimeout);