For software that creates a virtualized environment between the computer platform and its operating system, see Virtual machine. For virtual machines running desktop environments, see Desktop virtualization.

In computing, a virtual desktop is a term used with respect to user interfaces, usually within the WIMP paradigm, to describe ways in which the size of a computer's desktop environment is expanded beyond the physical limits of the screen's real estate through the use of software.

Switching desktops

Switchable desktops were designed and implemented at Xerox PARC as "Rooms" by D.A. Henderson and Stuart Card in 1986 based upon work by Patrick P. Chan in 1984. This work was covered by a US patent.

Switchable desktops were introduced to a much larger audience by Tom LaStrange in swm (the Solbourne Window Manager, for the X Window System) in 1989. ("Virtual Desktop" was originally a trademark of Solbourne Computer.) Rather than simply being placed at an x, y position on the computer's display, windows of running applications are then placed at x, y positions on a given virtual desktop “context”. They are then only accessible to the user if that particular context is enabled. A switching desktop provides a way for the user to switch between "contexts", or pages of screen space, only one of which can be displayed on the computer's display at any given time.

List of Window Managers that provide switching desktops

• aewm++
• ctwm - Supports up to 32 desktops
• cwm
• flwm
• icewm - Supports up to 12 desktops
• integrity
• ion2
• jwm - Supports up to 8 desktops
• larswm - Supports up to 4 desktops
• oroborus
• pwm2
• virtuawin
• whim
• windowmaker

Scrolling desktops

Other kinds of virtual desktop environments do not offer discrete virtual screens, but instead make it possible to "scroll" around a view that is larger than the available hardware is capable of displaying. For example, if a graphics card has a maximum resolution that is higher than the monitor's display resolution, the virtual desktop manager may allow windows to be placed "off the edge" of the screen. The user can then scroll to them by moving the mouse pointer to the edge of the display. The visible part of the larger virtual screen is called a viewport.

Amiga

The first platform to implement multiple desktop display as a hardware feature was Amiga 1000, released in 1985. The Amiga moved on to succeed in the consumer and video production market. All Amigas supported multiple in-memory screens displayed concurrently via the use of the graphics co-processor, AKA the "Copper". The Copper was a simple processor whose operations waited for a screen position, wrote to hardware registers (including display memory fetch position), conditionally skipped an instruction, or performed No OPeration [NOP]. Using the GUI implemented in system ROM API's, programs could transparently display multiple independent screens, from non-consecutive memory, without moving the memory. This hardware-based scrolling does not use blitting, but something more like what is sometimes called hardware panning. The video output is simply told (once, or many times) where to display (scanline) and from what screen memory address. A screen can move to any position, or display any portion, by modifying the wait, or fetch position. Typically a single byte value. The Copperlist did need to be sorted in vertical and horizontal wait position in order to function. Note: See http://www.faqs.org/faqs/amiga/books/ for a list of reference material.

Each desktop or 'screen' could have its own colour depth (number of available colours) and resolution, including use of interlacing. The display chipset ('graphics card' on a PC) could switch between these desktop modes on the fly, and during the drawing of a single screen, usually with three pixel deep line between each desktop shown on the screen. However, if one interlaced (flickering) desktop was displayed, all desktops onscreen would be similarly affected.

Some programs, VWorlds (an astronomy simulator) being an example, used the multiple desktops feature to overlay a set of controls over the main display screen. The controls could then be dragged up and down in order to show more or less of the main display.

In 1988 with the release of the Amiga A2024 monitor which added Amiga a vast choice of displaying various high-resolutions and in addition with Amiga graphic cards resolutions on which to run a Higher Resolution Workbench Desktop. Previous version only supported PAL or NTSC display modes.

Windows

Microsoft Windows does not implement virtual desktops at installation time. Historically video card implementors have provided this functionality, such as Nvidia's nView product.

Microsoft provides a Virtual Desktop PowerToy (for Windows XP), a software-based virtual desktop manager, which simulates many desktops, by minimizing and maximizing windows in groups, each group being a different desktop. However, the functionality provided is less comprehensive than that of many other virtual desktop solutions (e. g. maintain a window in a given desktop even when its application bar button flashes, etc.). Application compatibility problems are common, because application developers do not expect virtual desktops to be in use on the Windows platform.

Users of Microsoft Windows can use third-party software for advanced virtual desktop visualization, such as 3D virtual desktop managers that emulate some of the eye-candy features available on Compiz.

Many desktop shell replacements for Windows, including LiteStep, bblean, GeoShell, SharpE, Emerge Desktop and others, support virtual desktops via optional modules.