Add back support for EventDispatcher::schedule to accept a nullptr.

Also add a test to ensure we don't regress on this again.

Author: wengxt

src/lib/fcitx-utils/eventdispatcher.cpp

@@ -65,14 +65,14 @@ void EventDispatcher::detach() {
 
 void EventDispatcher::schedule(std::function<void()> functor) {
     FCITX_D();
-    if (!functor) {
-        return;
-    }
     std::lock_guard<std::mutex> lock(d->mutex_);
-    if (!d->asyncEvent_) {
-        return;
+    // functor can be null and we will still trigger async event.
+    if (functor) {
+        if (!d->asyncEvent_) {
+            return;
+        }
+        d->eventList_.push(std::move(functor));
     }
-    d->eventList_.push(std::move(functor));
     d->asyncEvent_->send();
 }
 

test/testeventdispatcher.cpp

@@ -6,10 +6,12 @@
  */
 #include <unistd.h>
 #include <atomic>
+#include <mutex>
 #include <thread>
 #include <vector>
 #include "fcitx-utils/event.h"
 #include "fcitx-utils/eventdispatcher.h"
+#include "fcitx-utils/eventloopinterface.h"
 #include "fcitx-utils/log.h"
 #include "fcitx-utils/trackableobject.h"
 
@@ -102,11 +104,43 @@ void withContext() {
     FCITX_ASSERT(!invalidCalled);
 }
 
+void scheduleNull() {
+    EventLoop e;
+    EventDispatcher dispatcher;
+    std::mutex readyLock;
+    bool ready = false;
+    // Post event may run immediately after exec, so we need a "ready" to ensure
+    // it is after schedule the event.
+    auto post = e.addPostEvent([&ready, &readyLock, &e](EventSource *) {
+        FCITX_INFO() << "POST IO";
+        {
+            std::lock_guard<std::mutex> lock(readyLock);
+            if (ready) {
+                e.exit();
+            }
+        }
+        return true;
+    });
+    dispatcher.attach(&e);
+    std::thread thread([&dispatcher, &ready, &readyLock]() {
+        sleep(2);
+        {
+            std::lock_guard<std::mutex> lock(readyLock);
+            ready = true;
+        }
+        // Test schedule nullptr is accepted.
+        dispatcher.schedule(nullptr);
+    });
+    e.exec();
+    thread.join();
+}
+
 int main() {
     fcitx::Log::setLogRule("*=5");
     basicTest();
     testOrder();
     recursiveSchedule();
     withContext();
+    scheduleNull();
     return 0;
 }