mcp-freecad

# Final FreeCAD AI Addon Crash Fix Summary ## Overview Successfully fixed all crash issues in the FreeCAD AI addon. The addon now loads and runs stably without segmentation faults. ## Summary of All Fixes Applied ### 1. QTimer.singleShot Crashes (15 occurrences fixed) **Issue**: QTimer.singleShot calls with lambda functions were causing segmentation faults during workbench switching. **Files Fixed**: - `freecad-ai/gui/providers_widget.py` (4 occurrences) - `freecad-ai/gui/connection_widget.py` (2 occurrences) - `freecad-ai/gui/unified_connection_widget.py` (6 occurrences) - `freecad-ai/gui/agent_control_widget.py` (1 occurrence) - `freecad-ai/gui/conversation_widget.py` (1 occurrence) - `freecad-ai/gui/server_widget.py` (1 occurrence) **Solution**: Replaced all `QTimer.singleShot(delay, lambda: method())` calls with direct `method()` calls. ### 2. AttributeError: 'status_label' not found **Issue**: Signal handlers were being called before the UI was fully initialized, trying to access `self.status_label` before it existed. **File Fixed**: `freecad-ai/gui/main_widget.py` **Solution**: Added `hasattr(self, "status_label")` checks in all signal handlers: - `_on_provider_status_changed()` - `_on_providers_updated()` - `_on_agent_mode_changed()` - `_on_agent_state_changed()` ### 3. Qt Signal Creation During Workbench Activation **Issue**: The most critical issue - Qt signals were being created at module import time, causing crashes during workbench activation. **File Fixed**: `freecad-ai/ai/provider_integration_service.py` **Root Cause**: - `ProviderIntegrationService` was inheriting from `QtCore.QObject` - Qt signals were being defined as class attributes - PySide2 was imported at module level - This caused Qt object creation during workbench switching, before Qt was ready **Solution**: Complete refactoring to remove all Qt dependencies: 1. Removed PySide2 import at module level 2. Removed inheritance from QtCore.QObject 3. Removed Qt Signal definitions 4. Implemented a pure Python callback-based system that mimics Qt's signal/slot interface 5. Created signal-like properties that return callback handlers with `connect()` and `emit()` methods ### 4. Provider Service Initialization Timing **File Fixed**: `freecad-ai/gui/main_widget.py` **Changes**: - Moved provider initialization from `_setup_provider_service()` to `_final_connection_check()` - Added `enable_signals()` call before provider initialization - Ensures providers are only initialized after the UI is completely ready ## Technical Details ### The Callback System The new callback system in `provider_integration_service.py` provides a Qt-signal-like interface without any Qt dependencies: ```python @property def provider_added(self): """Signal-like interface for provider_added callbacks.""" class CallbackSignal: def connect(self, callback): # Add callback to list def emit(self, *args): # Call all callbacks return CallbackSignal(self.provider_added_callbacks) ``` This allows the existing code to use the familiar `signal.connect()` and `signal.emit()` pattern without requiring Qt. ## Result - FreeCAD starts without crashes - Workbench switching works properly - All UI components load correctly - Provider service initialization works as expected - No segmentation faults ## Key Learnings 1. **Never use QTimer.singleShot with lambda functions in FreeCAD addons** - they cause crashes during widget initialization 2. **Never inherit from QObject or use Qt signals during module import** - Qt must be fully initialized first 3. **Always check for UI element existence before using them in callbacks** - signals may fire before UI is ready 4. **Defer all Qt-related initialization until after workbench activation** - use callback systems for early initialization