2 files changed, 61 insertions, 0 deletions

diff --git a/include/mbgl/util/run_loop.hpp b/include/mbgl/util/run_loop.hpp
index 5cde95a531..c89b8bd795 100644
--- a/include/mbgl/util/run_loop.hpp
+++ b/include/mbgl/util/run_loop.hpp
@@ -48,6 +48,15 @@ public:
     void runOnce();
     void stop();
 
+    using PlatformCallback = std::function<void()>;
+
+    // Platform integration callback for platforms that do not have full
+    // run loop integration or don't want to block at the Mapbox GL Native
+    // loop. It will be called from any thread and is up to the platform
+    // to, after receiving the callback, call RunLoop::runOnce() from the
+    // same thread as the Map object lives.
+    void setPlatformCallback(PlatformCallback&& callback) { platformCallback = std::move(callback); }
+
     // So far only needed by the libcurl backend.
     void addWatch(int fd, Event, std::function<void(int, Event)>&& callback);
     void removeWatch(int fd);
@@ -95,6 +104,7 @@ private:
             defaultQueue.emplace(std::move(task));
         }
         wake();
+        platformCallback();
     }
 
     void process() {
@@ -117,6 +127,8 @@ private:
         }
     }
 
+    PlatformCallback platformCallback = [] {};
+
     Queue defaultQueue;
     Queue highPriorityQueue;
     std::mutex mutex;
diff --git a/test/util/run_loop.test.cpp b/test/util/run_loop.test.cpp
index 4d2c704421..62bfbb0fc1 100644
--- a/test/util/run_loop.test.cpp
+++ b/test/util/run_loop.test.cpp
@@ -3,6 +3,10 @@
 
 #include <mbgl/test/util.hpp>
 
+#include <atomic>
+#include <condition_variable>
+#include <thread>
+
 using namespace mbgl::util;
 
 TEST(RunLoop, Stop) {
@@ -64,3 +68,48 @@ TEST(RunLoop, Priorities) {
 
     EXPECT_EQ((std::vector<int>{ 2, 4, 1, 3 }), order);
 }
+
+TEST(RunLoop, PlatformIntegration) {
+    std::atomic<int> count1(0);
+
+    // No need to be atomic, it will run
+    // on the main thread.
+    int count2(0);
+
+    std::thread::id mainThread = std::this_thread::get_id();
+
+    RunLoop loop;
+
+    std::mutex mutex;
+    std::condition_variable cv;
+
+    loop.setPlatformCallback([&] {
+        EXPECT_NE(mainThread, std::this_thread::get_id());
+        count1++;
+        cv.notify_one();
+    });
+
+    auto threadBody = [&]() {
+        for (unsigned i = 0; i < 100000; ++i) {
+            loop.invoke([&] {
+                EXPECT_EQ(mainThread, std::this_thread::get_id());
+                count2++;
+            });
+        }
+    };
+
+    std::thread thread1(threadBody);
+    std::thread thread2(threadBody);
+
+    while (count2 < 200000) {
+        std::unique_lock<std::mutex> lock(mutex);
+        cv.wait(lock);
+        loop.runOnce();
+    }
+
+    EXPECT_EQ(count1, 200000);
+    EXPECT_EQ(count2, 200000);
+
+    thread1.join();
+    thread2.join();
+}