fix: add task runner for linux. (#1821)

* fix: add task runner for linux.

* update.

linux/CMakeLists.txt

@@ -24,6 +24,7 @@ add_library(${PLUGIN_NAME} SHARED
   "flutter/core_implementations.cc"
   "flutter/standard_codec.cc"
   "flutter/plugin_registrar.cc"
+  "task_runner_linux.cc"
 )
 
 include_directories(

linux/flutter_webrtc_plugin.cc

@@ -2,6 +2,7 @@
 
 #include "flutter_common.h"
 #include "flutter_webrtc.h"
+#include "task_runner_linux.h"
 
 const char* kChannelName = "FlutterWebRTC.Method";
 
@@ -37,7 +38,7 @@ class FlutterWebRTCPluginImpl : public FlutterWebRTCPlugin {
 
   TextureRegistrar* textures() { return textures_; }
 
-  TaskRunner* task_runner() { return nullptr; }
+  TaskRunner* task_runner() { return task_runner_.get(); }
 
  private:
   // Creates a plugin that communicates on the given channel.
@@ -45,7 +46,8 @@ class FlutterWebRTCPluginImpl : public FlutterWebRTCPlugin {
                           std::unique_ptr<MethodChannel> channel)
       : channel_(std::move(channel)),
         messenger_(registrar->messenger()),
-        textures_(registrar->texture_registrar()) {
+        textures_(registrar->texture_registrar()),
+        task_runner_(std::make_unique<TaskRunnerLinux>()) {
     webrtc_ = std::make_unique<FlutterWebRTC>(this);
   }
 
@@ -63,6 +65,7 @@ class FlutterWebRTCPluginImpl : public FlutterWebRTCPlugin {
   std::unique_ptr<FlutterWebRTC> webrtc_;
   BinaryMessenger* messenger_;
   TextureRegistrar* textures_;
+  std::unique_ptr<TaskRunner> task_runner_;
 };
 
 }  // namespace flutter_webrtc_plugin

linux/task_runner_linux.cc

@@ -0,0 +1,31 @@
+#include "task_runner_linux.h"
+
+#include <glib.h>
+
+namespace flutter_webrtc_plugin {
+
+void TaskRunnerLinux::EnqueueTask(TaskClosure task) {
+  {
+    std::lock_guard<std::mutex> lock(tasks_mutex_);
+    tasks_.push(std::move(task));
+  }
+
+  GMainContext* context = g_main_context_default();
+  if (context) {
+    g_main_context_invoke(
+        context,
+        [](gpointer user_data)  -> gboolean {
+          TaskRunnerLinux* runner = static_cast<TaskRunnerLinux*>(user_data);
+          std::lock_guard<std::mutex> lock(runner->tasks_mutex_);
+          while (!runner->tasks_.empty()) {
+            TaskClosure task = std::move(runner->tasks_.front());
+            runner->tasks_.pop();
+            task();
+          }
+          return G_SOURCE_REMOVE;
+        },
+        this);
+  }
+}
+
+}  // namespace flutter_webrtc_plugin

linux/task_runner_linux.h

@@ -0,0 +1,26 @@
+#ifndef PACKAGES_FLUTTER_WEBRTC_LINUX_TASK_RUNNER_LINUX_H_
+#define PACKAGES_FLUTTER_WEBRTC_LINUX_TASK_RUNNER_LINUX_H_
+
+#include <memory>
+#include <mutex>
+#include <queue>
+#include "task_runner.h"
+
+namespace flutter_webrtc_plugin {
+
+class TaskRunnerLinux : public TaskRunner {
+ public:
+  TaskRunnerLinux() = default;
+  ~TaskRunnerLinux() override = default;
+
+  // TaskRunner implementation.
+  void EnqueueTask(TaskClosure task) override;
+
+ private:
+  std::mutex tasks_mutex_;
+  std::queue<TaskClosure> tasks_;
+};
+
+}  // namespace flutter_webrtc_plugin
+
+#endif  // PACKAGES_FLUTTER_WEBRTC_LINUX_TASK_RUNNER_LINUX_H_