Nontopmost

Nontopmost is a term used in graphical user interface (GUI) design and window management to describe a window or element that is not currently the topmost window. The topmost window is the one that is actively in focus, meaning it receives all keyboard and mouse input and is displayed above all other windows. When a window is nontopmost, it is still visible but is obscured by the topmost window or other windows in front of it.

In most operating systems, users can interact with multiple windows simultaneously. The concept of a topmost window is crucial for managing this interaction, ensuring that input is directed to the intended application. A nontopmost window, while not receiving direct input, may still be relevant to the user's task. For instance, a user might be typing in a document window (the topmost) while referring to information in a web browser window (a nontopmost) in the background.

The visual appearance of a nontopmost window can vary between operating systems and window managers. Typically, it will appear visually distinct from the topmost window, often with a less prominent title bar or a muted color scheme. Users can bring a nontopmost window to the front, making it the new topmost window, through various actions such as clicking on its title bar or using keyboard shortcuts like Alt+Tab. Understanding the distinction between topmost and nontopmost windows is fundamental to efficient multitasking in a GUI environment.