Support dragging and dropping of files onto app icon

Tested on macos and windows.  Drag and drop files onto either the dock icon or task bar icon once SavvyCCAN is running

mainwindow.cpp

@@ -807,6 +807,50 @@ void MainWindow::handleLoadFile()
     }
 }
 
+void MainWindow::handleDroppedFile(const QString &filename)
+{
+    QProgressDialog progress(qApp->activeWindow());
+    progress.setWindowModality(Qt::WindowModal);
+    progress.setLabelText("Loading file...");
+    progress.setCancelButton(nullptr);
+    progress.setRange(0,0);
+    progress.setMinimumDuration(0);
+    progress.show();
+    
+    QVector<CANFrame> loadedFrames;
+    bool loadResult = FrameFileIO::autoDetectLoadFile(filename, &loadedFrames);
+    
+    progress.cancel();
+    
+    if (!loadResult)
+    {
+        if (loadedFrames.count() > 0) //only ask if at least one frame was decoded.
+        {
+            QMessageBox::StandardButton confirmDialog = QMessageBox::question(this, "Error Loading", "Do you want to salvage what could be loaded?",
+                                      QMessageBox::Yes|QMessageBox::No);
+            if (confirmDialog == QMessageBox::Yes)
+            {
+                loadResult = true;
+            }
+        }
+    }
+
+    if (loadResult)
+    {
+        ui->canFramesView->scrollToTop();
+        model->clearFrames();
+        model->insertFrames(loadedFrames);
+        loadedFileName = filename;
+        model->recalcOverwrite();
+        ui->lbNumFrames->setText(QString::number(model->rowCount()));
+        if (ui->cbAutoScroll->isChecked()) ui->canFramesView->scrollToBottom();
+
+        updateFileStatus();
+        emit framesUpdated(-1);
+    }
+}
+
+
 void MainWindow::handleSaveFile()
 {
     QString filename;