[core] Add Scheduler::scheduleAndReplyValue() API

1 files changed, 27 insertions, 0 deletions

diff --git a/include/mbgl/actor/scheduler.hpp b/include/mbgl/actor/scheduler.hpp
index bb2cf124b8..1115328797 100644
--- a/include/mbgl/actor/scheduler.hpp
+++ b/include/mbgl/actor/scheduler.hpp
@@ -50,6 +50,18 @@ public:
     // first invoked, the call is ignored.
     std::function<void()> bindOnce(std::function<void()>);
 
+    // Enqueues the given |task| for execution into this scheduler's task queue and
+    // then enqueues the |reply| with the captured task result to the current
+    // task queue.
+    //
+    // The |TaskFn| return type must be compatible with the |ReplyFn| argument type.
+    // Note: the task result is copied and passed by value.
+    template <typename TaskFn, typename ReplyFn>
+    void scheduleAndReplyValue(const TaskFn& task, const ReplyFn& reply) {
+        assert(GetCurrent());
+        scheduleAndReplyValue(task, reply, GetCurrent()->makeWeakPtr());
+    }
+
     // Set/Get the current Scheduler for this thread
     static Scheduler* GetCurrent();
     static void SetCurrent(Scheduler*);
@@ -58,6 +70,21 @@ public:
     // will lazily initialize a shared worker pool when ran
     // from the first time.
     static std::shared_ptr<Scheduler> GetBackground();
+
+protected:
+    template <typename TaskFn, typename ReplyFn>
+    void scheduleAndReplyValue(const TaskFn& task,
+                               const ReplyFn& reply,
+                               mapbox::base::WeakPtr<Scheduler> replyScheduler) {
+        auto scheduled = [replyScheduler, task, reply] {
+            auto lock = replyScheduler.lock();
+            if (!replyScheduler) return;
+            auto scheduledReply = [reply, result = task()] { reply(result); };
+            replyScheduler->schedule(std::move(scheduledReply));
+        };
+
+        schedule(std::move(scheduled));
+    }
 };
 
 } // namespace mbgl