qt: Support deferred start of jobs

* lang/qt/src/job.cpp, lang/qt/src/job.h (Job::startNow): New method.
* lang/qt/src/job_p.h (JobPrivate::start): New pure virtual method.
* lang/qt/src/qgpgmechangeexpiryjob.cpp
(QGpgMEChangeExpiryJobPrivate::start): New.
* lang/qt/src/qgpgmeencryptjob.cpp (QGpgMEEncryptJobPrivate::start):
New.
* lang/qt/src/qgpgmeimportjob.cpp (QGpgMEImportJobPrivate::start): New.
* lang/qt/src/qgpgmelistallkeysjob.cpp
(QGpgMEListAllKeysJobPrivate::start): New.
* lang/qt/src/qgpgmesignencryptjob.cpp
(QGpgMESignEncryptJobPrivate::start): New.
* lang/qt/src/threadedjobmixin.h (Thread::hasFunction): New method.
(ThreadedJobMixin::run, ThreadedJobMixin::setWorkerFunction): New
methods.
--

startNow() starts a deferred job for which the worker function has been
set before.

GnuPG-bug-id: 6323

NEWS

@@ -28,6 +28,7 @@ Noteworthy changes in version 1.18.1 (unreleased)
  qt: ListAllKeysJob::Options                NEW.
  qt: ListAllKeysJob::setOptions             NEW.
  qt: ListAllKeysJob::options                NEW.
+ qt: Job::startNow                          NEW.
 
 
 Noteworthy changes in version 1.18.0 (2022-08-10)

lang/qt/src/job.cpp

@@ -137,6 +137,13 @@ GpgME::Context *QGpgME::Job::context(QGpgME::Job *job)
     return QGpgME::g_context_map.value (job, nullptr);
 }
 
+void QGpgME::Job::startNow()
+{
+    auto d = getJobPrivate(this);
+    Q_ASSERT(d && "This Job class has no JobPrivate class");
+    d->start();
+}
+
 #define make_job_subclass_ext(x,y)                \
     QGpgME::x::x( QObject * parent ) : y( parent ) {} \
     QGpgME::x::~x() {}

lang/qt/src/job.h

@@ -95,6 +95,13 @@ public:
      */
     static GpgME::Context *context(Job *job);
 
+    /** Starts a deferred job.
+     *
+     * The job needs to have been prepared for a deferred start by calling the
+     * startLater() function instead of the start() function of a leaf class.
+     */
+    void startNow();
+
 public Q_SLOTS:
     virtual void slotCancel() = 0;
 

lang/qt/src/job_p.h

@@ -46,6 +46,8 @@ class JobPrivate
 {
 public:
     virtual ~JobPrivate() {}
+
+    virtual void start() = 0;
 };
 
 // Setter and getters for the externally stored pimpl instances of jobs

lang/qt/src/qgpgmechangeexpiryjob.cpp

@@ -64,6 +64,12 @@ public:
     }
 
     ~QGpgMEChangeExpiryJobPrivate() override = default;
+
+private:
+    void start() override
+    {
+        q->run();
+    }
 };
 
 }

lang/qt/src/qgpgmeencryptjob.cpp

@@ -70,6 +70,12 @@ public:
     }
 
     ~QGpgMEEncryptJobPrivate() override = default;
+
+private:
+    void start() override
+    {
+        q->run();
+    }
 };
 
 }

lang/qt/src/qgpgmeimportjob.cpp

@@ -65,6 +65,12 @@ public:
     }
 
     ~QGpgMEImportJobPrivate() override = default;
+
+private:
+    void start() override
+    {
+        q->run();
+    }
 };
 
 }

lang/qt/src/qgpgmelistallkeysjob.cpp

@@ -75,6 +75,12 @@ public:
     }
 
     ~QGpgMEListAllKeysJobPrivate() override = default;
+
+private:
+    void start() override
+    {
+        q->run();
+    }
 };
 
 }

lang/qt/src/qgpgmesignencryptjob.cpp

@@ -71,6 +71,12 @@ public:
     }
 
     ~QGpgMESignEncryptJobPrivate() override = default;
+
+private:
+    void start() override
+    {
+        q->run();
+    }
 };
 
 }

lang/qt/src/threadedjobmixin.h

@@ -103,6 +103,12 @@ public:
         m_function = function;
     }
 
+    bool hasFunction()
+    {
+        const QMutexLocker locker(&m_mutex);
+        return static_cast<bool>(m_function);
+    }
+
     T_result result() const
     {
         const QMutexLocker locker(&m_mutex);
@@ -127,6 +133,12 @@ public:
     typedef ThreadedJobMixin<T_base, T_result> mixin_type;
     typedef T_result result_type;
 
+    void run()
+    {
+        Q_ASSERT(m_thread.hasFunction() && "Call setWorkerFunction() before run()");
+        m_thread.start();
+    }
+
 protected:
     static_assert(std::tuple_size<T_result>::value > 2,
                   "Result tuple too small");
@@ -166,6 +178,12 @@ protected:
         QGpgME::g_context_map.remove(this);
     }
 
+    template <typename T_binder>
+    void setWorkerFunction(const T_binder &func)
+    {
+        m_thread.setFunction([this, func]() { return func(this->context()); });
+    }
+
     template <typename T_binder>
     void run(const T_binder &func)
     {