Framebuffer - Virtual Framebuffers

Virtual Framebuffers

Many systems attempt to emulate the function of a framebuffer device, often for reasons of compatibility. The two most common "virtual" framebuffers are the Linux framebuffer device (fbdev) and the X Virtual Framebuffer (Xvfb). The X Virtual Framebuffer was added to the X Window System distribution to provide a method for running X without a graphical framebuffer. While the original reasons for this are lost to history, it is often used on modern systems to support programs such as the Sun Microsystems JVM that do not allow dynamic graphics to be generated in a headless environment.

The Linux framebuffer device was developed to abstract the physical method for accessing the underlying framebuffer into a guaranteed memory map that is easy for programs to access. This increases portability, as programs are not required to deal with systems that have disjointed memory maps or require bank switching.