keyPressEvent

keyPressEvent is a virtual function in the Qt framework that is called whenever a key is pressed while a widget has focus. It is a member of the QObject class and is designed to be overridden by subclasses to handle keyboard input. When a key is pressed, Qt dispatches a QKeyEvent object to the widget that currently has input focus. This QKeyEvent object contains information about the key that was pressed, such as its key code and any modifier keys that were held down (e.g., Shift, Ctrl, Alt).

By reimplementing the keyPressEvent function in a custom widget, developers can define specific actions to be performed in response to different key presses. For instance, a text editor might use keyPressEvent to insert characters into the document, while a game might use it to move a character or trigger an action. The reimplemented function typically checks the key code of the QKeyEvent to determine which key was pressed and then executes the appropriate code. It is also common practice to call the base class implementation of keyPressEvent within the overridden function, usually at the end, to ensure that standard key handling behavior, such as character input for text widgets, is not inadvertently disabled. This allows for a combination of custom and default keyboard event processing.