[core] Decouple Scheduler interface from actor model

So that it is possible to schedule normal `std::function` and use `mapbox::base::WeakPtr`.

3 files changed, 15 insertions, 10 deletions

diff --git a/src/mbgl/actor/mailbox.cpp b/src/mbgl/actor/mailbox.cpp
index dfe0520790..070e14bdb0 100644
--- a/src/mbgl/actor/mailbox.cpp
+++ b/src/mbgl/actor/mailbox.cpp
@@ -27,7 +27,7 @@ void Mailbox::open(Scheduler& scheduler_) {
     }
     
     if (!queue.empty()) {
-        (*scheduler)->schedule(shared_from_this());
+        (*scheduler)->schedule(makeClosure(shared_from_this()));
     }
 }
 
@@ -57,7 +57,7 @@ void Mailbox::push(std::unique_ptr<Message> message) {
     bool wasEmpty = queue.empty();
     queue.push(std::move(message));
     if (wasEmpty && scheduler) {
-        (*scheduler)->schedule(shared_from_this());
+        (*scheduler)->schedule(makeClosure(shared_from_this()));
     }
 }
 
@@ -84,14 +84,20 @@ void Mailbox::receive() {
     (*message)();
 
     if (!wasEmpty) {
-        (*scheduler)->schedule(shared_from_this());
+        (*scheduler)->schedule(makeClosure(shared_from_this()));
     }
 }
 
+// static
 void Mailbox::maybeReceive(std::weak_ptr<Mailbox> mailbox) {
     if (auto locked = mailbox.lock()) {
         locked->receive();
     }
 }
 
+// static
+std::function<void()> Mailbox::makeClosure(std::weak_ptr<Mailbox> mailbox) {
+    return [mailbox]() { maybeReceive(mailbox); };
+}
+
 } // namespace mbgl
diff --git a/src/mbgl/util/thread_pool.cpp b/src/mbgl/util/thread_pool.cpp
index e839d1b4be..d8df0cd575 100644
--- a/src/mbgl/util/thread_pool.cpp
+++ b/src/mbgl/util/thread_pool.cpp
@@ -26,11 +26,10 @@ ThreadPool::ThreadPool(std::size_t count) {
                     return;
                 }
 
-                auto mailbox = queue.front();
+                auto function = std::move(queue.front());
                 queue.pop();
                 lock.unlock();
-
-                Mailbox::maybeReceive(mailbox);
+                if (function) function();
             }
         });
     }
@@ -49,10 +48,10 @@ ThreadPool::~ThreadPool() {
     }
 }
 
-void ThreadPool::schedule(std::weak_ptr<Mailbox> mailbox) {
+void ThreadPool::schedule(std::function<void()> fn) {
     {
         std::lock_guard<std::mutex> lock(mutex);
-        queue.push(mailbox);
+        queue.push(std::move(fn));
     }
 
     cv.notify_one();
diff --git a/src/mbgl/util/thread_pool.hpp b/src/mbgl/util/thread_pool.hpp
index 509fd06061..96fc13bda5 100644
--- a/src/mbgl/util/thread_pool.hpp
+++ b/src/mbgl/util/thread_pool.hpp
@@ -15,11 +15,11 @@ public:
     explicit ThreadPool(std::size_t count);
     ~ThreadPool() override;
 
-    void schedule(std::weak_ptr<Mailbox>) override;
+    void schedule(std::function<void()>) override;
 
 private:
     std::vector<std::thread> threads;
-    std::queue<std::weak_ptr<Mailbox>> queue;
+    std::queue<std::function<void()>> queue;
     std::mutex mutex;
     std::condition_variable cv;
     bool terminate{ false };