Display loading indicator when launching in the standalone app

neurotic/gui/standalone.py

@@ -15,6 +15,7 @@
 from packaging import version
 
 import quantities as pq
+import neo
 from ephyviewer import QT, QT_MODE
 
 from .. import __version__, _elephant_tools, default_log_level, log_file
@@ -63,6 +64,7 @@ class MainWindow(QT.QMainWindow):
     """
 
     request_download = QT.pyqtSignal()
+    request_load_dataset = QT.pyqtSignal()
 
     def __init__(self, file=None, initial_selection=None, lazy=True, theme='light', ui_scale='small', support_increased_line_width=False, show_datetime=False):
         """
@@ -104,15 +106,37 @@ def __init__(self, file=None, initial_selection=None, lazy=True, theme='light',
 
         # metadata selector
         self.metadata_selector = _MetadataSelectorQt(self)
-        self.setCentralWidget(self.metadata_selector)
+
+        # loading label
+        loading_label = QT.QLabel('Launching, please wait...')
+        loading_label.setFrameStyle(QT.QFrame.Panel | QT.QFrame.Sunken)
+        loading_label.setAlignment(QT.Qt.AlignCenter)
+        loading_label.setStyleSheet('font: 14pt')
+
+        # initially stack the metadata selector above the loading label
+        self.stacked_layout = QT.QStackedLayout()
+        self.stacked_layout.addWidget(self.metadata_selector)  # index 0
+        self.stacked_layout.addWidget(loading_label)           # index 1
+        central_widget = QT.QWidget()
+        central_widget.setLayout(self.stacked_layout)
+        self.setCentralWidget(central_widget)
 
         # create a worker thread for downloading data
         self.download_thread = QT.QThread()
-        self.download_worker = _DownloadWorker(self.metadata_selector)
+        self.download_worker = _DownloadWorker(self)
         self.download_worker.moveToThread(self.download_thread)
         self.request_download.connect(self.download_worker.download)
         self.download_worker.download_finished.connect(self.on_download_finished)
 
+        # create a worker thread for loading datasets
+        self.load_dataset_thread = QT.QThread()
+        self.load_dataset_worker = _LoadDatasetWorker(self)
+        self.load_dataset_worker.moveToThread(self.load_dataset_thread)
+        self.request_load_dataset.connect(self.load_dataset_worker.load_dataset)
+        self.load_dataset_worker.load_dataset_finished.connect(self.on_load_dataset_finished)
+        self.load_dataset_worker.show_status_msg.connect(self.statusBar().showMessage)
+        self.blk = None
+
         # construct the menus
         self.create_menus()
 
@@ -170,9 +194,9 @@ def create_menus(self):
         do_open_directory.setShortcut('Ctrl+F')
         do_open_directory.triggered.connect(self.open_directory)
 
-        do_launch = file_menu.addAction('&Launch')
-        do_launch.setShortcut('Return')
-        do_launch.triggered.connect(self.launch)
+        self.do_launch = file_menu.addAction('&Launch')
+        self.do_launch.setShortcut('Return')
+        self.do_launch.triggered.connect(self.start_launch)
 
         options_menu = self.menuBar().addMenu(self.tr('&Options'))
 
@@ -319,24 +343,43 @@ def open_directory(self):
             self.statusBar().showMessage('Folder not found locally (need to '
                                          'download?)', msecs=5000)
 
-    def launch(self):
+    def start_launch(self):
         """
-        Load data for the selected dataset and launch the ephyviewer window.
+        Load data for the selected dataset in a separate thread.
         """
 
-        metadata = self.metadata_selector.selected_metadata
+        self.do_launch.setText('&Launch in progress!')
+        self.do_launch.setEnabled(False)
+        self.metadata_selector.setEnabled(False)
+        self.stacked_layout.setCurrentIndex(1)  # show loading label
+        self.load_dataset_thread.start()
+        self.request_load_dataset.emit()
+
+    def on_load_dataset_finished(self):
+        """
+        Launch the ephyviewer window after loading the dataset.
+        """
+
+        self.load_dataset_thread.quit()
 
         try:
 
-            blk = load_dataset(metadata, lazy=self.lazy)
+            if self.blk is None:
+                pass
+
+            elif not isinstance(self.blk, neo.Block):
+                raise ValueError('blk must be a Neo Block but instead is '
+                                 f'{self.blk}')
 
-            ephyviewer_config = EphyviewerConfigurator(metadata, blk, self.lazy)
-            ephyviewer_config.show_all()
+            else:
+                metadata = self.metadata_selector.selected_metadata
+                ephyviewer_config = EphyviewerConfigurator(metadata, self.blk, self.lazy)
+                ephyviewer_config.show_all()
 
-            win = ephyviewer_config.create_ephyviewer_window(theme=self.theme, ui_scale=self.ui_scale, support_increased_line_width=self.support_increased_line_width, show_datetime=self.show_datetime)
-            self.windows.append(win)
-            win.destroyed.connect(lambda qobject, i=len(self.windows)-1: self.free_resources(i))
-            win.show()
+                win = ephyviewer_config.create_ephyviewer_window(theme=self.theme, ui_scale=self.ui_scale, support_increased_line_width=self.support_increased_line_width, show_datetime=self.show_datetime)
+                self.windows.append(win)
+                win.destroyed.connect(lambda qobject, i=len(self.windows)-1: self.free_resources(i))
+                win.show()
 
         except FileNotFoundError as e:
 
@@ -353,6 +396,13 @@ def launch(self):
             self.statusBar().showMessage('Launch failed (see console for '
                                          'details)', msecs=5000)
 
+        finally:
+
+            self.do_launch.setText('&Launch')
+            self.do_launch.setEnabled(True)
+            self.metadata_selector.setEnabled(True)
+            self.stacked_layout.setCurrentIndex(0)  # show metadata selector
+
     def toggle_debug_logging(self, checked):
         """
         Toggle log filtering level between its original level and debug mode
@@ -445,7 +495,6 @@ def show_about(self):
 
         import platform
         import ephyviewer
-        import neo
         import numpy
         import pyqtgraph
         try:
@@ -517,8 +566,10 @@ def free_resources(self, i):
         the issue, see https://github.com/NeuralEnsemble/python-neo/issues/684.
         """
 
-        # first remove the last remaining reference to the closed window
+        # first remove the last remaining references to the closed window and
+        # Neo Block
         self.windows[i] = None
+        self.blk = None
 
         # run garbage collection
         gc.collect()
@@ -541,7 +592,7 @@ def __init__(self, parent):
         self.setStyleSheet('font: 9pt Courier;')
 
         self.currentRowChanged.connect(self._on_select)
-        self.itemDoubleClicked.connect(self.parent().launch)
+        self.itemDoubleClicked.connect(self.parent().start_launch)
 
     def _on_select(self, currentRow):
         """
@@ -590,19 +641,69 @@ class _DownloadWorker(QT.QObject):
 
     download_finished = QT.pyqtSignal()
 
-    def __init__(self, metadata_selector):
+    def __init__(self, mainwindow):
         """
         Initialize a new _DownloadWorker.
         """
 
         QT.QObject.__init__(self)
 
-        self.metadata_selector = metadata_selector
+        self.mainwindow = mainwindow
 
     def download(self):
         """
         Download all files and emit a signal when complete.
         """
 
-        self.metadata_selector.download_all_data_files()
+        self.mainwindow.metadata_selector.download_all_data_files()
         self.download_finished.emit()
+
+
+class _LoadDatasetWorker(QT.QObject):
+    """
+    A thread worker for loading data sets.
+    """
+
+    load_dataset_finished = QT.pyqtSignal()
+    show_status_msg = QT.pyqtSignal(str, int)
+
+    def __init__(self, mainwindow):
+        """
+        Initialize a new _LoadDatasetWorker.
+        """
+
+        QT.QObject.__init__(self)
+
+        self.mainwindow = mainwindow
+
+    def load_dataset(self):
+        """
+        Load the selected dataset.
+        """
+
+        metadata = self.mainwindow.metadata_selector.selected_metadata
+        lazy = self.mainwindow.lazy
+
+        try:
+
+            self.mainwindow.blk = load_dataset(metadata, lazy=lazy)
+
+        except FileNotFoundError as e:
+
+            logger.error('Some files were not found locally and may need to '
+                         f'be downloaded: {e}')
+            self.show_status_msg.emit('Launch failed because some files are '
+                                     'missing (need to download?)', 5000)
+            self.mainwindow.blk = None
+
+        except Exception:
+
+            logger.exception('Encountered a fatal error. Traceback will be '
+                             'written to log file.')
+            self.show_status_msg.emit('Launch failed (see console for '
+                                      'details)', 5000)
+            self.mainwindow.blk = None
+
+        finally:
+
+            self.load_dataset_finished.emit()