qt-signals-slots

To define custom signals in PySide6 or PyQt6, you declare them as class attributes and emit them using the new-style syntax. This mechanism enables robust inter-object communication without tight coupling between components.

The best way to handle cross-thread communication in Qt is using signals and slots with queued connections. This ensures safe multithreading by automatically posting events to the receiver's thread event loop.

The @Slot decorator in Python marks a method as a Qt slot, defining its signature for signal connections. It ensures proper type matching when connecting signals to slots for inter-object communication.

Auto, Direct, and Queued connection types in Qt determine how signals invoke slots. Direct calls immediately, Queued posts to the receiver's event loop, and Auto selects based on the thread context.

Qt signals fail to trigger connected slots due to incorrect syntax, mismatched signatures, or disconnected objects. Debugging involves verifying connection statements and ensuring lambda captures are correct.