From 10a2eb03e1d931016d70d05783a3ddb157e389a9 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Marko=20Markovi=C4=87?= <okram@civokram.com>
Date: Sat, 11 Jul 2026 00:19:46 +0400
Subject: [PATCH] Stop PRINT_REDIRECTOR from outliving the LogViewer

PRINT_REDIRECTOR is a module-level singleton, so the lambda connected to
sigStdoutWrite in prepare_panes accumulated one connection per MainWindow and
was never disconnected. Each lambda also closed over self and resolved
self.components["log"] late through a dict that MainMixin holds as a class
attribute, so it reached whichever LogViewer registered last. Once a LogViewer
was destroyed, the next print() called into a deleted C++ object and raised
RuntimeError.

Connecting the bound method instead lets PyQt drop the connection when the
receiver is destroyed.
---
 cq_editor/main_window.py  |  8 +++++---
 tests/test_main_window.py | 37 +++++++++++++++++++++++++++++++++++++
 2 files changed, 42 insertions(+), 3 deletions(-)
 create mode 100644 tests/test_main_window.py

diff --git a/cq_editor/main_window.py b/cq_editor/main_window.py
index bece4094..986e8f44 100644
--- a/cq_editor/main_window.py
+++ b/cq_editor/main_window.py
@@ -291,9 +291,11 @@ def prepare_panes(self):
         for d in self.docks.values():
             d.show()
 
-        PRINT_REDIRECTOR.sigStdoutWrite.connect(
-            lambda text: self.components["log"].append(text)
-        )
+        # Connect the bound method rather than a lambda: PRINT_REDIRECTOR is a
+        # module-level singleton, and PyQt drops a connection to a QObject's
+        # bound method when that QObject is destroyed. A lambda would outlive
+        # the LogViewer and call into a deleted C++ object.
+        PRINT_REDIRECTOR.sigStdoutWrite.connect(self.components["log"].append)
 
     def prepare_menubar(self):
 
diff --git a/tests/test_main_window.py b/tests/test_main_window.py
new file mode 100644
index 00000000..fef7fe1e
--- /dev/null
+++ b/tests/test_main_window.py
@@ -0,0 +1,37 @@
+import sys
+
+from PyQt5.QtWidgets import QMessageBox
+from PyQt5 import sip
+
+from cq_editor.__main__ import MainWindow
+from cq_editor.main_window import PRINT_REDIRECTOR
+
+
+def test_print_redirector_released_with_window(qtbot, mocker):
+    """
+    PRINT_REDIRECTOR is a module-level singleton that outlives any MainWindow.
+    Once a window's LogViewer is destroyed, a write must be dropped rather than
+    delivered to the now-deleted C++ object (which raises "wrapped C/C++ object
+    of type LogViewer has been deleted").
+    """
+
+    mocker.patch.object(QMessageBox, "question", return_value=QMessageBox.Yes)
+    mocker.patch.object(QMessageBox, "warning", return_value=QMessageBox.Discard)
+
+    win = MainWindow()
+    qtbot.addWidget(win)
+
+    # destroy this window's LogViewer, as tearing the window down would
+    sip.delete(win.components["log"])
+
+    # PyQt routes an exception raised inside a slot to sys.excepthook rather
+    # than propagating it, so capture it there while emitting
+    errors = []
+    original_hook = sys.excepthook
+    sys.excepthook = lambda exc_type, *rest: errors.append(exc_type)
+    try:
+        PRINT_REDIRECTOR.sigStdoutWrite.emit("stray output after close")
+    finally:
+        sys.excepthook = original_hook
+
+    assert errors == []