Prevent full application freeze when writing keychainchunks to keycha…

…in on certain systems (e.g. macOS)

Signed-off-by: Claudio Cambra <claudio.cambra@nextcloud.com>

src/libsync/creds/keychainchunk.cpp

@@ -12,6 +12,7 @@
  * for more details.
  */
 
+#include "QtConcurrent/qtconcurrentrun.h"
 #include "account.h"
 #include "keychainchunk.h"
 #include "theme.h"
@@ -212,16 +213,21 @@ void WriteJob::slotWriteJobDone(QKeychain::Job *incomingJob)
                 _account->id()
             ) : keyWithIndex;
 
-        auto job = new QKeychain::WritePasswordJob(_serviceName, this);
-#if defined(KEYCHAINCHUNK_ENABLE_INSECURE_FALLBACK)
-        addSettingsToJob(_account, job);
-#endif
-        job->setInsecureFallback(_insecureFallback);
-        connect(job, &QKeychain::Job::finished, this, &KeychainChunk::WriteJob::slotWriteJobDone);
-        // only add the key's (sub)"index" after the first element, to stay compatible with older versions and non-Windows
-        job->setKey(kck);
-        job->setBinaryData(chunk);
-        job->start();
+        // On certain OSes (e.g. macOS) writing to the keychain blocks the main thread.
+        // Since QtKeychain does not (yet) run this operation on a separate thread,
+        // we run this with QtConcurrent to prevent a full application freeze.
+        QtConcurrent::run([kck, chunk, this] {
+            auto job = new QKeychain::WritePasswordJob(_serviceName, this);
+    #if defined(KEYCHAINCHUNK_ENABLE_INSECURE_FALLBACK)
+            addSettingsToJob(_account, job);
+    #endif
+            job->setInsecureFallback(_insecureFallback);
+            connect(job, &QKeychain::Job::finished, this, &KeychainChunk::WriteJob::slotWriteJobDone);
+            // only add the key's (sub)"index" after the first element, to stay compatible with older versions and non-Windows
+            job->setKey(kck);
+            job->setBinaryData(chunk);
+            job->start();
+        });
 
         chunk.clear();
     } else {