Show dialog box for uncaught exceptions in Qt

corrscope/gui/__init__.py

@@ -2,6 +2,7 @@ import functools
 import signal
 import sys
 import traceback
+from contextlib import contextmanager
 from pathlib import Path
 from types import MethodType
 from typing import (
@@ -43,7 +44,6 @@ from corrscope.gui.model_bind import (
     Symbol,
     SymbolText,
     BoundComboBox,
-    _call_all,
 )
 from corrscope.gui.util import color2hex, Locked, find_ranges, TracebackDialog
 from corrscope.gui.view_mainwindow import MainWindow as Ui_MainWindow
@@ -70,6 +70,19 @@ def res(file: str) -> str:
     return str(APP_DIR / file)
 
 
+@contextmanager
+def exception_as_dialog(window: qw.QWidget):
+    def excepthook(exc_type, exc_val, exc_tb):
+        TracebackDialog(window).showMessage(format_stack_trace(exc_val))
+
+    orig = sys.excepthook
+    try:
+        sys.excepthook = excepthook
+        yield
+    finally:
+        sys.excepthook = orig
+
+
 def gui_main(cfg_or_path: Union[Config, Path]):
     # Allow Ctrl-C to exit
     signal.signal(signal.SIGINT, signal.SIG_DFL)
@@ -88,7 +101,13 @@ def gui_main(cfg_or_path: Union[Config, Path]):
 
     app = qw.QApplication(sys.argv)
     window = MainWindow(cfg_or_path)
-    sys.exit(app.exec_())
+    # Any exceptions raised within MainWindow() will be caught within exec_.
+    # exception_as_dialog() turns it into a Qt dialog.
+    with exception_as_dialog(window):
+        sys.exit(app.exec_())
+        # Any exceptions raised after exec_ terminates will call
+        # exception_as_dialog().__exit__ before being caught.
+        # This produces a Python traceback.
 
 
 class MainWindow(qw.QMainWindow, Ui_MainWindow):
@@ -533,11 +552,20 @@ class MainWindow(qw.QMainWindow, Ui_MainWindow):
         QDesktopServices.openUrl(qc.QUrl(help_url))
 
 
-def format_stack_trace(e):
+def _format_exc_value(e: BaseException, limit=None, chain=True):
+    """Like traceback.format_exc() but takes an exception object."""
+    list = traceback.format_exception(
+        type(e), e, e.__traceback__, limit=limit, chain=chain
+    )
+    str = "".join(list)
+    return str
+
+
+def format_stack_trace(e: BaseException):
     if isinstance(e, CorrError):
-        stack_trace = traceback.format_exc(limit=0)
+        stack_trace = _format_exc_value(e, limit=0)
     else:
-        stack_trace = traceback.format_exc()
+        stack_trace = _format_exc_value(e)
     return stack_trace