What do signal and slot mean in PyQt5?

What do signal and slot mean in PyQt5?

This is a brief explanation of the concept of signal and slot in PyQt5, which is the GUI framework for QGIS plugins. In summary, this very much resembles events and callbacks in JavaScript. It’s an asynchronous mechanism to let one part of a program know when another part of a program was updated, which is a most crucial concept in GUI programming.

When does the qgisinterface signal get emitted?

Emitted whenever current (selected) layer changes. Signal emitted when the current theme is changed so plugins can change their tool button icons. This signal is emitted after a layout designer window is closed. This signal is emitted when a new layout designer has been opened.

What does signal and slot mean in QGIS?

You master signal / slot, you master a whole lot about plugin development in QGIS. Generally a signal is a trigger which can be emitted (hence the term signal) and carry an arbitrary amount of information when it is emitted.

How to return native project action in QGIS?

Returns the Hide Deselected Layers action. Returns the native identify action. Returns the native map tips action. Returns the native measure action. Returns the native measure area action. Returns the native Move Features action. Returns the native new bookmark action. Returns the native New Project action. Returns the Open Project action.

What is the parent class of QGIS widget?

Any QGIS widget and almost all GUI classes are descendants of QObject (i.e. have QObject as the very basic parent class) and they all come with predefined signals, such as QgsFilterLineEdit ‘s valueChanged signal, which is triggered when a user changes the text of the widget.

How is a signal connected to a slot in Python?

Generally a signal is a trigger which can be emitted (hence the term signal) and carry an arbitrary amount of information when it is emitted. The signal can be connected to a slot, which needs to be Python callable (in other words, a method or a class, anything implementing the __call__ magic), which can be any arbitrary function.