xenial (7) directvnc-kbmapping.7.gz

NAME

       directvnc-kbmapping - Details of keyboard mapping file syntax for directvnc(1)

Xmodmap Keyboard Layout File Syntax

       General  syntax  of the xmodmap keyboard layout file is described in the xmodmap(1x) manual page. For the
       purposes of keyboard switching implementation in directvnc, the following subset of its syntax is used:

       Comments (lines starting with an exclamation mark) are recognized as such, and ignored Expressions  using
       keycode  are  recognized  with  up  to four keysym values, used as described in the mentioned manual page
       Other xmodmap expressions will be ignored.  So, the following is a valid syntax of an xmodmap  file  that
       can be converted into a directvnc keyboard layout file:

                Key    Base     Shift          Mode               Mode+Shift

       keycode  13     = 4      dollar         4                  quotedbl
       keycode  14     = 5      percent        5                  colon
       keycode  15     = 6      asciicircum    6                  comma
       keycode  16     = 7      ampersand      7                  period
       keycode  24     = q      Q              Cyrillic_shorti    Cyrillic_SHORTI
       keycode  25     = w      W              Cyrillic_tse       Cyrillic_TSE
       keycode  26     = e      E              Cyrillic_u         Cyrillic_U
       keycode  27     = r      R              Cyrillic_ka        Cyrillic_KA

       An example of a xmodmap file for Cyrillic input can be found ????

Directvnc Keyboard Layout File Syntax

       The  xmodmap  file  uses  character  identifiers to identify keysyms that keycodes will be translated to.
       While this works in the original xmodmap program which acts as a client to the X server it loads keyboard
       layout into (xmodmap queries the X server to convert symbolic keysym identifiers into numeric), directvnc
       is not supposed to interact with the remote Xvnc server this way. Instead, a derivative format  is  used,
       which contains hexadecimal codes for keysyms:

       keycode 13 0x034 0x024 0x034 0x022
       keycode 14 0x035 0x025 0x035 0x03a
       keycode 15 0x036 0x05e 0x036 0x02c
       keycode 16 0x037 0x026 0x037 0x02e
       keycode 24 0x071 0x051 0x6ca 0x6ea
       keycode 25 0x077 0x057 0x6c3 0x6e3
       keycode 26 0x065 0x045 0x6d5 0x6f5
       keycode 27 0x072 0x052 0x6cb 0x6eb
       keycode 28 0x074 0x054 0x6c5 0x6e5
       keycode 29 0x079 0x059 0x6ce 0x6ee
       keycode 30 0x075 0x055 0x6c7 0x6e7

       The  keycode  keyword  does  not play any role at the moment, but is preserved for the future extensions,
       when other xmodmap expressions may also be recognized.

Conversion From One to Another

       As noted above, directvnc does not query the remote Xvnc server for keysyms' numeric values. There is the
       keysymdef.h include file which contains all the necessary information. In particular, considering this (a
       small portion of the keysymdef.h file):

       #define XK_Q                   0x051
       #define XK_q                   0x071
       #define XK_Cyrillic_shorti     0x6ca
       #define XK_Cyrillic_SHORTI     0x6ea

       it becomes clear how to convert

       keycode 24   = q   Q   Cyrillic_shorti   Cyrillic_SHORTI

       into

       keycode 24 0x071 0x051 0x6ca 0x6ea

       The directvnc-xmapconv(1) utility reads an xmodmap syntax  file  from  standard  input,  and  writes  the
       directvnc compatible syntax file to standard output.

       Inside,  the script runs its standard input through the C preprocessor including the keysymdef.h file and
       prepending each keysym identifier with XK_. The directvnc keyboard  layout  file  mentioned  earlier  was
       produced exactly this way out of the xmodmap file for Cyrillic input.

Key Modifiers Logic

       The  directvnc's  keyboard  layout  switching  module  holds  an internal table where the contents of the
       keyboard layout file is read into. The module intercepts all keyboard input obtained from  DirectFB,  and
       uses  keyboard  scan  code  plus  8  (also known as the MIN_KEYCODE constant) as index into that table to
       determine whether any mapping exists for a given keycode.

       The directvnc's keyboard layout switching module uses the ScrollLock key as mode lock: when  its  LED  is
       on,  the  third  or fourth keysym would be transmitted (depending on the Shift and CapsLock status); when
       Scroll lock LED is off, the first or the second keysym would be transmitted.

       The Alt or AltGr keys are not used to control keyboard mode.

       For letters, Shift and CapsLock are XORed. For numbers, CapsLock does not apply.

       If Ctrl is pressed, or there was no keyboard layout file specified, or the keyboard layout file does  not
       contain any mapping for a given keycode, directvnc performs its default translation of keyboard code into
       a keysym using its hardcoded ISO-8859-1 translation table.

SEE ALSO

       directvnc(1), directvnc-xmapconv(1), xmodmap(1)

AUTHOR

       Dimitry Golubovsky, Loris Boillet

                                                  Jul 30, 2011                            directvnc-kbmapping(7)