1.6 Terminology

A number of terms are used in a GLUT-specific manner throughout this document. The GLUT meaning of these terms is independent of the window system GLUT is used with. Here are GLUT-specific meanings for the following GLUT-specific terms:

 Callback

A programmer specified routine that can be registered with GLUT to be called in response to a specific type of event. Also used to refer to a specific callback routine being called.

 Colormap

A mapping of pixel values to RGB color values. Use by color index windows.

 Dials and button box

A sophisticated input device consisting of a pad of buttons and an array of rotating dials, often used by computer-aided design programs.

 Display mode

A set of OpenGL frame buffer capabilities that can be attributed to a window.

 Idle

A state when no window system events are received for processing as callbacks and the idle callback, if one is registered, is called.

 Layer in use

Either the normal plane or overlay. This per-window state determines what frame buffer layer OpenGL commands affect.

 Menu entry

A menu item that the user can select to trigger the menu callback for the menu entry's value.

 Menu item

Either a menu entry or a sub-menu trigger.

 Modifiers

The Shift, Ctrl, and Alt keys that can be held down simultaneously with a key or mouse button being pressed or released.

 Multisampling

A technique for hardware antialiasing generally available only on expensive 3D graphics hardware [1]. Each pixel is composed of a number of samples (each containing color and depth information). The samples are averaged to determine the displayed pixel color value. Multisampling is supported as an extension to OpenGL.

 Normal plane

The default frame buffer layer where GLUT window state resides; as opposed to the overlay.

 Overlay

A frame buffer layer that can be displayed preferentially to the normal plane and supports transparency to display through to the normal plane. Overlays are useful for rubber-banding effects, text annotation, and other operations, to avoid damaging the normal plane frame buffer state. Overlays require hardware support not present on all systems.

 Pop

The act of forcing a window to the top of the stacking order for sibling windows.

 Pop-up menu

A menu that can be set to appear when a specified mouse button is pressed in a window. A pop-menu consists of multiple menu items.

 Push

The act of forcing a window to the bottom of the stacking order for sibling windows.

 Reshape

The act of changing the size or shape of the window.

 Spaceball

A sophisticated 3D input device that provides six degrees of freedom, three axes of rotation and three axes of translation. It also supports a number of buttons. The device is a hand-sized ball attached to a base. By cupping the ball with one's hand and applying torsional or directional force on the ball, rotations and translationsare generated.

 Stereo

A frame buffer capability providing left and right color buffers for creating stereoscopic renderings. Typically, the user wears LCD shuttered goggles synchronized with the alternating display on the screen of the left and right color buffers.

 Sub-menu

A menu cascaded from some sub-menu trigger.

 Sub-menu trigger

A menu item that the user can enter to cascade another pop-up menu.

 Subwindow

A type of window that is the child window of a top-level window or other subwindow. The drawing and visible region of a subwindow is limited by its parent window.

 Tablet

A precise 2D input device. Like a mouse, 2D coordinates are returned. The absolute position of the tablet ``puck'' on the tablet is returned. Tablets also support a number of buttons.

 Timer

A callback that can be scheduled to be called in a specified interval of time.

 Top-level window

A window that can be placed, moved, resized, etc. independently from other top-level windows by the user. Subwindows may reside within a top-level window.

 Window

A rectangular area for OpenGL rendering.

 Window display state

One of shown, hidden, or iconified. A shown window is potentially visible on the screen (it may be obscured by other windows and not actually visible). A hidden window will never be visible. An iconified window is not visible but could be made visible in response to some user action like clicking on the window's corresponding icon.

 Window system

A broad notion that refers to both the mechanism and policy of the window system. For example, in the X Window System both the window manager and the X server are integral to what GLUT considers the window system.