Graphical control element

A control element (sometimes called a control or widget) in a graphical user interface is an element of interaction, such as a button or a scroll bar. Controls are software components that a computer user interacts with through direct manipulation to read or edit information about an application. User interface libraries such as Windows Presentation Foundation, GTK+, and Cocoa, contain a collection of controls and the logic to render these.

Each widget facilitates a specific type of user-computer interaction, and appears as a visible part of the application's GUI as defined by the theme and rendered by the rendering engine. The theme makes all widgets adhere to a unified aesthetic design and creates a sense of overall cohesion. Some widgets support interaction with the user, for example labels, buttons, and check boxes. Others act as containers that group the widgets added to them, for example windows, panels, and tabs.

Structuring a user interface with widget toolkits allows developers to reuse code for similar tasks, and provides users with a common language for interaction, maintaining consistency throughout the whole information system.

Graphical user interface builders facilitate the authoring of GUIs in a WYSIWYG manner employing a user interface markup language. They automatically generate all the source code for a widget from general descriptions provided by the developer, usually through direct manipulation.

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