Add utils/debug.py

qutebrowser/utils/debug.py

@@ -0,0 +1,63 @@
+# Copyright 2014 Florian Bruhin (The Compiler) <mail@qutebrowser.org>
+#
+# This file is part of qutebrowser.
+#
+# qutebrowser 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.
+#
+# qutebrowser 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 qutebrowser.  If not, see <http://www.gnu.org/licenses/>.
+
+"""Utilities used for debugging."""
+
+import sys
+
+from PyQt5.QtCore import pyqtRemoveInputHook
+
+try:
+    # pylint: disable=import-error
+    from ipdb import set_trace as pdb_set_trace
+except ImportError:
+    from pdb import set_trace as pdb_set_trace
+
+import qutebrowser.commands.utils as cmdutils
+
+
+@cmdutils.register(name='settrace', hide=True)
+def set_trace():
+    """Set a tracepoint in the Python debugger that works with Qt.
+
+    Based on http://stackoverflow.com/a/1745965/2085149
+
+    """
+    print()
+    print("When done debugging, remember to execute:")
+    print("  from PyQt5 import QtCore; QtCore.pyqtRestoreInputHook()")
+    print("before executing c(ontinue).")
+    pyqtRemoveInputHook()
+    return pdb_set_trace()
+
+
+def trace_lines(do_trace):
+    """Turn on/off printing each executed line.
+
+    Args:
+        do_trace: Whether to start tracing (True) or stop it (False).
+
+    """
+    def trace(frame, event, _):
+        """Trace function passed to sys.settrace."""
+        print("{}, {}:{}".format(event, frame.f_code.co_filename,
+                                 frame.f_lineno))
+        return trace
+    if do_trace:
+        sys.settrace(trace)
+    else:
+        sys.settrace(None)