 | This article needs additional citations for verification .(May 2007) |
Z-order is an ordering of overlapping two-dimensional objects, such as windows in a stacking window manager, shapes in a vector graphics editor, or objects in a 3D application. [1] One of the features of a typical GUI is that windows may overlap, so that one window hides part or all of another. When two windows overlap, their Z-order determines which one appears on top of the other.
The term "Z-order" refers to the order of objects along the Z-axis. In coordinate geometry, X typically refers to the horizontal axis (left to right), Y to the vertical axis (up and down), and Z refers to the axis perpendicular to the other two (forward or backward). One can think of the windows in a GUI as a series of planes parallel to the surface of the monitor. The windows are therefore stacked along the Z-axis, and the Z-order information thus specifies the front-to-back ordering of the windows on the screen. An analogy would be some sheets of paper scattered on top of a table, each sheet being a window, the table your computer screen, and the top sheet having the highest Z value.
Typically, users of a GUI can affect the Z-order by selecting a window to be brought to the foreground (that is, "above" or "in front of" all the other windows). Some window managers allow interaction with windows while they are not in the foreground, while others will bring a window to the front whenever it receives input from the user. It is also possible for special windows to be designated "always on top"; these are then fixed to the top of the Z-order so that (with few exceptions) no other window can overlap them.
When dealing with visual objects on a computer screen, an object with a Z-order of 1 would be visually "underneath" an object with a Z-order of 2 or greater. This is the same as making "layers" of objects where the Z-order determines what object is on top of another. An HTML page can use CSS to specify the Z-order so that some objects can be layered over others.
Z-ordering is also used in 3D applications to determine object visibility based on overlap from other objects. This confers a speed advantage to the user as the computer does not need to render unseen objects. [1] In practice, of course, some objects may be only partially obscured, and this is a complication that must be taken into account.
The actual number assigned to a particular place in the Z-order is sometimes known as the z-index. In particular the CSS property that sets the stack order of specific elements is known as the z-index. An element with greater stack order is always in front of another element with lower stack order. [2]
p{position:relative;z-index:-1;}Negative stack orders can also be used in the same manner. A negative value will appear behind a positive one. z-index only works on elements that have a position value (e.g. position: relative;) and for many coders, this one of the first things to investigate when debugging why the z-index isn't working. [3]
Like all other CSS properties, it can be set with JavaScript as well with the following syntax:
object.style.zIndex='1';The graphical user interface, or GUI, is a form of user interface that allows users to interact with electronic devices through graphical icons and audio indicators such as primary notation, instead of text-based UIs, typed command labels or text navigation. GUIs were introduced in reaction to the perceived steep learning curve of command-line interfaces (CLIs), which require commands to be typed on a computer keyboard.
2D computer graphics is the computer-based generation of digital images—mostly from two-dimensional models and by techniques specific to them. It may refer to the branch of computer science that comprises such techniques or to the models themselves.
Swing is a GUI widget toolkit for Java. It is part of Oracle's Java Foundation Classes (JFC) – an API for providing a graphical user interface (GUI) for Java programs.
An HTML element is a type of HTML document component, one of several types of HTML nodes. The first used version of HTML was written by Tim Berners-Lee in 1993 and there have since been many versions of HTML. The most commonly used version is HTML 4.01, which became official standard in December 1999. An HTML document is composed of a tree of simple HTML nodes, such as text nodes, and HTML elements, which add semantics and formatting to parts of document. Each element can have HTML attributes specified. Elements can also have content, including other elements and text.
Web colors are colors used in displaying web pages on the World Wide Web ; they can be described by way of three methods: a color may be specified as an RGB triplet, in hexadecimal format or according to its common English name in some cases. A color tool or other graphics software is often used to generate color values. In some uses, hexadecimal color codes are specified with notation using a leading number sign (#). A color is specified according to the intensity of its red, green and blue components, each represented by eight bits. Thus, there are 24 bits used to specify a web color within the sRGB gamut, and 16,777,216 colors that may be so specified.
In computing, an icon is a pictogram or ideogram displayed on a computer screen in order to help the user navigate a computer system. The icon itself is a quickly comprehensible symbol of a software tool, function, or a data file, accessible on the system and is more like a traffic sign than a detailed illustration of the actual entity it represents. It can serve as an electronic hyperlink or file shortcut to access the program or data. The user can activate an icon using a mouse, pointer, finger, or voice commands. Their placement on the screen, also in relation to other icons, may provide further information to the user about their usage. In activating an icon, the user can move directly into and out of the identified function without knowing anything further about the location or requirements of the file or code.
Inkscape is a free and open-source vector graphics editor for GNU/Linux, Windows and macOS. It offers a rich set of features and is widely used for both artistic and technical illustrations such as cartoons, clip art, logos, typography, diagramming and flowcharting. It uses vector graphics to allow for sharp printouts and renderings at unlimited resolution and is not bound to a fixed number of pixels like raster graphics. Inkscape uses the standardized Scalable Vector Graphics (SVG) file format as its main format, which is supported by many other applications including web browsers. It can import and export various other file formats, including SVG, AI, EPS, PDF, PS and PNG.
A screen reader is a form of assistive technology (AT) that renders text and image content as speech or braille output. Screen readers are essential to people who are blind, and are useful to people who are visually impaired, illiterate, or have a learning disability. Screen readers are software applications that attempt to convey what people with normal eyesight see on a display to their users via non-visual means, like text-to-speech, sound icons, or a braille device. They do this by applying a wide variety of techniques that include, for example, interacting with dedicated accessibility APIs, using various operating system features, and employing hooking techniques.
Ray casting is the methodological basis for 3D CAD/CAM solid modeling and image rendering. It is essentially the same as ray tracing for computer graphics where virtual light rays are "cast" or "traced" on their path from the focal point of a camera through each pixel in the camera sensor to determine what is visible along the ray in the 3D scene. The term "Ray Casting" was introduced by Scott Roth while at the General Motors Research Labs from 1978–1980. His paper, "Ray Casting for Modeling Solids", describes modeled solid objects by combining primitive solids, such as blocks and cylinders, using the set operators union (+), intersection (&), and difference (-). The general idea of using these binary operators for solid modeling is largely due to Voelcker and Requicha's geometric modelling group at the University of Rochester. See solid modeling for a broad overview of solid modeling methods. This figure on the right shows a U-Joint modeled from cylinders and blocks in a binary tree using Roth's ray casting system in 1979.
A stacking window manager is a window manager that draws and allows windows to overlap, without using a compositing algorithm. All window managers that allow the overlapping of windows but are not compositing window managers are considered stacking window managers, although it is possible that not all use exactly the same methods. Other window managers that are not considered stacking window managers are those that do not allow the overlapping of windows, which are called tiling window managers.
In 3D computer graphics, hidden-surface determination is the process of identifying what surfaces and parts of surfaces can be seen from a particular viewing angle. A hidden-surface determination algorithm is a solution to the visibility problem, which was one of the first major problems in the field of 3D computer graphics. The process of hidden-surface determination is sometimes called hiding, and such an algorithm is sometimes called a hider. When referring to line rendering it is known as hidden-line removal. Hidden-surface determination is necessary to render a scene correctly, so that one may not view features hidden behind the model itself, allowing only the naturally viewable portion of the graphic to be visible.
A graphical 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, Qt, GTK, and Cocoa, contain a collection of controls and the logic to render these.
A window manager is system software that controls the placement and appearance of windows within a windowing system in a graphical user interface. Most window managers are designed to help provide a desktop environment. They work in conjunction with the underlying graphical system that provides required functionality—support for graphics hardware, pointing devices, and a keyboard—and are often written and created using a widget toolkit.
The computer graphics pipeline, also known as the rendering pipeline or graphics pipeline, is a fundamental framework within computer graphics that outlines the necessary procedures for transforming a three-dimensional (3D) scene into a two-dimensional (2D) representation on a screen. Once a 3D model is generated, whether it's for a video game or any other form of 3D computer animation, the graphics pipeline becomes instrumental in converting the model into a visually perceivable format on the computer display. Due to the dependence on specific software, hardware configurations, and desired display attributes, a universally applicable graphics pipeline does not exist. Nevertheless, graphics application programming interfaces (APIs), such as Direct3D and OpenGL, were developed to standardize common procedures and oversee the graphics pipeline of a given hardware accelerator. These APIs provide an abstraction layer over the underlying hardware, relieving programmers from the need to write code explicitly targeting various graphics hardware accelerators like AMD, Intel, Nvidia, and others.
Clipping, in the context of computer graphics, is a method to selectively enable or disable rendering operations within a defined region of interest. Mathematically, clipping can be described using the terminology of constructive geometry. A rendering algorithm only draws pixels in the intersection between the clip region and the scene model. Lines and surfaces outside the view volume are removed.
In graphic design, page layout is the arrangement of visual elements on a page. It generally involves organizational principles of composition to achieve specific communication objectives.
A compositing manager, or compositor, is software that provides applications with an off-screen buffer for each window. The compositing manager composites the window buffers into an image representing the screen and writes the result into the display memory. A compositing window manager is a window manager that is also a compositing manager.
Cascading Style Sheets (CSS) is a style sheet language used for describing the presentation of a document written in a markup language such as HTML or XML. CSS is a cornerstone technology of the World Wide Web, alongside HTML and JavaScript.
The Abstract Window Toolkit (AWT) is Java's original platform-dependent windowing, graphics, and user-interface widget toolkit, preceding Swing. The AWT is part of the Java Foundation Classes (JFC) — the standard API for providing a graphical user interface (GUI) for Java program. AWT is also the GUI toolkit for a number of Java ME profiles. For example, Connected Device Configuration profiles require Java runtimes on mobile telephones to support the Abstract Window Toolkit.
CSS Flexible Box Layout, commonly known as Flexbox, is a CSS web layout model. It is in the W3C's candidate recommendation (CR) stage. The flex layout allows responsive elements within a container to be automatically arranged depending on viewport size.