1 files changed, 78 insertions, 0 deletions
diff --git a/share/extensions/inkex/gui/tester.py b/share/extensions/inkex/gui/tester.py
new file mode 100644
index 0000000..c8ce5e7
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+++ b/share/extensions/inkex/gui/tester.py
@@ -0,0 +1,78 @@
+# coding=utf-8
+#
+# Copyright 2022 Martin Owens <doctormo@geek-2.com>
+#
+# This program is free software: you can redistribute it and/or modify
+#  it under the terms of the GNU General Public License as published by
+#  the Free Software Foundation, either version 3 of the License, or
+#  (at your option) any later version.
+#
+#  This program is distributed in the hope that it will be useful,
+#  but WITHOUT ANY WARRANTY; without even the implied warranty of
+#  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+#  GNU General Public License for more details.
+#
+#  You should have received a copy of the GNU General Public License
+#  along with this program.  If not, see <http://www.gnu.org/licenses/>
+#
+"""
+Structures for consistant testing of Gtk GUI programs.
+"""
+
+import sys
+from gi.repository import Gtk, GLib
+
+
+class MainLoopProtection:
+    """
+    This protection class provides a way to launch the Gtk mainloop in a test
+    friendly way.
+
+    Exception handling hooks provide a way to see errors that happen
+        inside the main loop, raising them back to the caller.
+    A full timeout in seconds stops the gtk mainloop from operating
+        beyond a set time, acting as a kill switch in the event something
+        has gone horribly wrong.
+
+    Use:
+        with MainLoopProtection(timeout=10s):
+            app.run()
+    """
+
+    def __init__(self, timeout=10):
+        self.timeout = timeout * 1000
+        self._hooked = None
+        self._old_excepthook = None
+
+    def __enter__(self):
+        # replace sys.excepthook with our own and remember hooked raised error
+        self._old_excepthook = sys.excepthook
+        sys.excepthook = self.excepthook
+        # Remove mainloop by force if it doesn't die within 10 seconds
+        self._timeout = GLib.timeout_add(self.timeout, self.idle_exit)
+
+    def __exit__(self, exc, value, traceback):  # pragma: no cover
+        """Put the except handler back, cancel the timer and raise if needed"""
+        if self._old_excepthook:
+            sys.excepthook = self._old_excepthook
+        # Remove the timeout, so we don't accidentally kill later mainloops
+        if self._timeout:
+            GLib.source_remove(self._timeout)
+        # Raise an exception if one happened during the test run
+        if self._hooked:
+            exc, value, traceback = self._hooked
+        if value and traceback:
+            raise value.with_traceback(traceback)
+
+    def idle_exit(self):  # pragma: no cover
+        """Try to going to kill any running mainloop."""
+        GLib.idle_add(Gtk.main_quit)
+
+    def excepthook(self, ex_type, ex_value, traceback):  # pragma: no cover
+        """Catch errors thrown by the Gtk mainloop"""
+        self.idle_exit()
+        # Remember the exception data for raising inside the test context
+        if ex_value is not None:
+            self._hooked = [ex_type, ex_value, traceback]
+        # Fallback and double print the exception (remove if double printing is problematic)
+        return self._old_excepthook(ex_type, ex_value, traceback)