defer dnd move operations while the thumbviewer is busy

also remove dead code and handle idempotent dir moves correctly

mention in #28

Author: luebking

Phototonic.cpp

@@ -2029,8 +2029,6 @@ void Phototonic::deleteFromViewer(bool trash) {
             return;
         }
     }
-    while (thumbsViewer->isBusy())
-        QThread::sleep(30);
 
     QString trashError;
     if (trash ? (Trash::moveToTrash(fullPath, trashError) == Trash::Success) :
@@ -2979,11 +2977,16 @@ void Phototonic::dropOp(Qt::KeyboardModifiers keyMods, bool dirOp, QString copyM
         return;
     }
 
-    if (destDir == Settings::currentDirectory) {
+    if (destDir == (dirOp ? QFileInfo(copyMoveDirPath).absolutePath() : Settings::currentDirectory)) {
         msgBox.critical(tr("Error"), tr("Destination directory is the same as the source directory."));
         return;
     }
 
+    if (!Settings::isCopyOperation && thumbsViewer->isBusy()) { // defer, don't alter while the thumbsviewer is loading stuff
+        QTimer::singleShot(100, this, [=](){dropOp(keyMods, dirOp, copyMoveDirPath);});
+        return;
+    }
+
     if (dirOp) {
         QString baseName = copyMoveDirPath.section(QDir::separator(), -1);