[qt] Make MapboxGLMapRenderer a scheduler to receive messages when rendering

platform/qt/src/qmapboxgl_map_renderer.cpp

@@ -12,6 +12,12 @@ QMapboxGLMapRenderer::~QMapboxGLMapRenderer()
 {
 }
 
+void QMapboxGLMapRenderer::schedule(std::weak_ptr<mbgl::Mailbox> mailbox)
+{
+    std::lock_guard<std::mutex> lock(m_taskQueueMutex);
+    m_taskQueue.push(mailbox);
+}
+
 void QMapboxGLMapRenderer::updateParameters(std::shared_ptr<mbgl::UpdateParameters> newParameters)
 {
     std::lock_guard<std::mutex> lock(m_updateMutex);
@@ -29,8 +35,11 @@ void QMapboxGLMapRenderer::render()
     std::shared_ptr<mbgl::UpdateParameters> params;
     {
         // Lock on the parameters
-        std::unique_lock<std::mutex> lock(m_updateMutex);
-        if (!m_updateParameters) return;
+        std::lock_guard<std::mutex> lock(m_updateMutex);
+
+        if (!m_updateParameters) {
+            return;
+        }
 
         // Hold on to the update parameters during render
         params = m_updateParameters;
@@ -39,7 +48,20 @@ void QMapboxGLMapRenderer::render()
     // The OpenGL implementation automatically enables the OpenGL context for us.
     mbgl::BackendScope scope(m_backend, mbgl::BackendScope::ScopeType::Implicit);
 
+    Scheduler::SetCurrent(this);
+
     m_renderer->render(*params);
+
+    std::queue<std::weak_ptr<mbgl::Mailbox>> taskQueue;
+    {
+        std::unique_lock<std::mutex> lock(m_taskQueueMutex);
+        std::swap(taskQueue, m_taskQueue);
+    }
+
+    while (!taskQueue.empty()) {
+        mbgl::Mailbox::maybeReceive(taskQueue.front());
+        taskQueue.pop();
+    }
 }
 
 void QMapboxGLMapRenderer::setObserver(std::shared_ptr<mbgl::RendererObserver> observer)