WSDISPLAY(4)              OpenBSD Programmer's Manual             WSDISPLAY(4)

NAME
     wsdisplay - generic display device support in wscons

SYNOPSIS
     wsdisplay* at ega? console ?
     (EGA display on ISA)
     wsdisplay* at vga? console ?
     (VGA display on ISA or PCI)
     wsdisplay* at pcdisplay? console ?
     (generic PC (ISA) display)
     wsdisplay* at tga? console ?
     (DEC TGA display, alpha only)
     wsdisplay* at nextdisplay? console ?
     (NeXT display)
     wsdisplay* at sti? console ?
     (HP CRX and Visualize series framebuffers)
     wsdisplay0 at smg0
     (VAXstation small monochrome display)
     options WSDISPLAY_DEFAULTSCREENS=N

DESCRIPTION
     The wsdisplay driver is an abstraction layer for display devices within
     the wscons(4) framework.  It attaches to the hardware specific display
     device driver and makes it available as text terminal or graphics inter-
     face.

     A display device can have the ability to display characters on it (with-
     out help of an X server), either directly by hardware or through software
     drawing pixel data into the display memory.  Such displays are called
     ``emulating'', the wsdisplay driver will connect a terminal emulation
     module and provide a tty-like software interface.  In contrary, non-emu-
     lating displays can only be used by special programs like X servers.

     The console locator in the configuration line refers to the device's use
     as output part of the operating system console.  A device specification
     containing a positive value here will only match if the device is in use
     as system console.  (The console device selection in early system startup
     is not influenced.)  This way, the console device can be connected to a
     known wsdisplay(4) device instance.  (Naturally, only ``emulating'' dis-
     play devices are usable as console.)

     The logical unit of an independent contents displayed on a display (some-
     times referred to as ``virtual terminal'' ) is called a ``screen'' here.
     If the underlying device driver supports it, multiple screens can be used
     on one display.  (As of this writing, only the vga(4) and the VAX ``smg''
     display drivers provide this ability.)  Screens have different minor de-
     vice numbers and separate tty instances.  One screen possesses the
     ``focus'', this means it is displayed on the display and its tty device
     will get the keyboard input.  (In some cases, if no screen is set up or
     if a screen was just deleted, it is possible that no focus is present at
     all.)  The focus can be switched by either special keyboard input (typi-
     cally CTL-ALT-Fn) or an ioctl command issued by a user program.  Screens
     are set up or deleted through the /dev/ttyCcfg control decice (preferably
     using the wsconscfg(8) utility).  Alternatively, the compile-time option
     WSDISPLAY_DEFAULTSCREENS=N will set up N screens of the display driver's
     default type and using the system's default terminal emulator at autocon-
     figuration time.

     In addition and with help from backend drivers the following features are
     also provided:



     o   Loading, deleting and listing the loaded fonts.

     o   Browsing backwards in the screen output, the size of the buffer for
         saved text is defined by the particular hardware driver.

     o   Blanking the screen by timing out on inactivity in the screen holding
         the input focus.  Awakening activities consist of:

         o   pressing any keys on the keyboard;
         o   moving or clicking the mouse;
         o   any output to the screen.

         Blanking the screen is usually done by disabling the horizontal sync
         signal on video output, but may also include blanking the vertical
         sync in which case most monitors go into power saving mode.  See ws-
         consctl(8) for controlling variables.

     Consult the back-end drivers' documentation for which features are sup-
     ported for each particular hardware type.

FILES
     /dev/ttyC*                          terminal devices (per screen)
     /dev/ttyCcfg                        control device
     /usr/include/dev/wscons/wsconsio.h

SEE ALSO
     ega(4), pcdisplay(4), tty(4), tga(4), vga(4), wscons(4), wsconscfg(8),
     wsconsctl(8), wsfontload(8)

BUGS
     The wsdisplay code currently limits the number of screens on one display
     to 8.

     The terms ``wscons'' and ``wsdisplay'' are not cleanly distinguished in
     the code and in manual pages.

     ``non-emulating'' display devices are not tested.

OpenBSD 3.0                     March 20, 1999                               2
