Allow passing in Labels to app.main (#1524)

* Allow passing in `Labels` to `app.main`

* Load the labels object through command

* Add warning when unable to switch back to CPU mode

sleap/gui/app.py

@@ -49,6 +49,8 @@
 import platform
 import random
 import re
+import traceback
+from logging import getLogger
 from pathlib import Path
 from typing import Callable, List, Optional, Tuple
 
@@ -85,6 +87,9 @@
 from sleap.util import parse_uri_path
 
 
+logger = getLogger(__name__)
+
+
 class MainWindow(QMainWindow):
     """The SLEAP GUI application.
 
@@ -101,6 +106,7 @@ class MainWindow(QMainWindow):
     def __init__(
         self,
         labels_path: Optional[str] = None,
+        labels: Optional[Labels] = None,
         reset: bool = False,
         no_usage_data: bool = False,
         *args,
@@ -118,7 +124,7 @@ def __init__(
         self.setAcceptDrops(True)
 
         self.state = GuiState()
-        self.labels = Labels()
+        self.labels = labels or Labels()
 
         self.commands = CommandContext(
             state=self.state, app=self, update_callback=self.on_data_update
@@ -175,8 +181,10 @@ def __init__(
             print("Restoring GUI state...")
             self.restoreState(prefs["window state"])
 
-        if labels_path:
+        if labels_path is not None:
             self.commands.loadProjectFile(filename=labels_path)
+        elif labels is not None:
+            self.commands.loadLabelsObject(labels=labels)
         else:
             self.state["project_loaded"] = False
 
@@ -1594,8 +1602,7 @@ def _show_keyboard_shortcuts_window(self):
         ShortcutDialog().exec_()
 
 
-def main(args: Optional[list] = None):
-    """Starts new instance of app."""
+def create_parser():
 
     import argparse
 
@@ -1635,6 +1642,13 @@ def main(args: Optional[list] = None):
         default=False,
     )
 
+    return parser
+
+
+def main(args: Optional[list] = None, labels: Optional[Labels] = None):
+    """Starts new instance of app."""
+
+    parser = create_parser()
     args = parser.parse_args(args)
 
     if args.nonnative:
@@ -1651,12 +1665,23 @@ def main(args: Optional[list] = None):
     app.setWindowIcon(QtGui.QIcon(sleap.util.get_package_file("gui/icon.png")))
 
     window = MainWindow(
-        labels_path=args.labels_path, reset=args.reset, no_usage_data=args.no_usage_data
+        labels_path=args.labels_path,
+        labels=labels,
+        reset=args.reset,
+        no_usage_data=args.no_usage_data,
     )
     window.showMaximized()
 
     # Disable GPU in GUI process. This does not affect subprocesses.
-    sleap.use_cpu_only()
+    try:
+        sleap.use_cpu_only()
+    except RuntimeError:  # Visible devices cannot be modified after being initialized
+        logger.warning(
+            "Running processes on the GPU. Restarting your GUI should allow switching "
+            "back to CPU-only mode.\n"
+            "Received the following error when trying to switch back to CPU-only mode:"
+        )
+        traceback.print_exc()
 
     # Print versions.
     print()

sleap/gui/commands.py

@@ -36,7 +36,7 @@ class which inherits from `AppCommand` (or a more specialized class such as
 from enum import Enum
 from glob import glob
 from pathlib import Path, PurePath
-from typing import Callable, Dict, Iterator, List, Optional, Tuple, Type
+from typing import Callable, Dict, Iterator, List, Optional, Tuple, Type, Union
 
 import attr
 import cv2
@@ -260,16 +260,15 @@ def loadLabelsObject(self, labels: Labels, filename: Optional[str] = None):
         """
         self.execute(LoadLabelsObject, labels=labels, filename=filename)
 
-    def loadProjectFile(self, filename: str):
+    def loadProjectFile(self, filename: Union[str, Labels]):
         """Loads given labels file into GUI.
 
         Args:
-            filename: The path to the saved labels dataset. If None,
-                then don't do anything.
+            filename: The path to the saved labels dataset or the `Labels` object.
+                If None, then don't do anything.
 
         Returns:
             None
-
         """
         self.execute(LoadProjectFile, filename=filename)
 
@@ -647,9 +646,8 @@ def do_action(context: "CommandContext", params: dict):
 
         Returns:
             None.
-
         """
-        filename = params["filename"]
+        filename = params.get("filename", None)  # If called with just a Labels object
         labels: Labels = params["labels"]
 
         context.state["labels"] = labels
@@ -669,7 +667,9 @@ def do_action(context: "CommandContext", params: dict):
             context.state["video"] = labels.videos[0]
 
         context.state["project_loaded"] = True
-        context.state["has_changes"] = params.get("changed_on_load", False)
+        context.state["has_changes"] = params.get("changed_on_load", False) or (
+            filename is None
+        )
 
         # This is not listed as an edit command since we want a clean changestack
         context.app.on_data_update([UpdateTopic.project, UpdateTopic.all])
@@ -683,17 +683,16 @@ def ask(context: "CommandContext", params: dict):
         if len(filename) == 0:
             return
 
-        gui_video_callback = Labels.make_gui_video_callback(
-            search_paths=[os.path.dirname(filename)], context=params
-        )
-
         has_loaded = False
         labels = None
-        if type(filename) == Labels:
+        if isinstance(filename, Labels):
             labels = filename
             filename = None
             has_loaded = True
         else:
+            gui_video_callback = Labels.make_gui_video_callback(
+                search_paths=[os.path.dirname(filename)], context=params
+            )
             try:
                 labels = Labels.load_file(filename, video_search=gui_video_callback)
                 has_loaded = True