Add comment to explain loop logic

Author: lolgab

core/loop.scala

@@ -9,6 +9,20 @@ object EventLoop {
   // Schedule loop execution after main ends
   scalanative.runtime.ExecutionContext.global.execute(
     new Runnable {
+      /**
+        * This is the implementation of the event loop
+        * that integrates with libuv. The logic is the
+        * following:
+        * - First we run all Scala futures in the default
+        *   execution context
+        * - Then in loop:
+        *   - we check if they generated IO calls on
+        *     the event loop
+        *   - If it's the case we run libuv's event loop
+        *     using UV_RUN_ONCE that blocks only once
+        *   - We run the default execution context again
+        *     in case the callbacks generated new Futures
+        */
       def run(): Unit = {
         scala.scalanative.runtime.loop()
         while (uv_loop_alive(loop) != 0) {