d.mon

NAME

d.mon - To establish and control use of a graphics display monitor.
(GRASS Display Program)

SYNOPSIS

d.mon
d.mon help
d.mon [-lLprs] [start=name] [stop=name] [select=name] [unlock=name] [nlev=value]

DESCRIPTION

The GRASS program d.mon allows the user to start, select, list, query the status of, release control of, stop, and unlock control of, available graphics monitors. The user can run this program either interactively (through a series of menus), or non-interactively by typing the name of the monitor to start, stop, select, or unlock, and any desired flags on the command line.

Flags:

-l: List all monitors
-L: List all monitors (with current status)
-p: Print name of currently selected monitor
-r: Release currently selected monitor
-s: Do not automatically select when starting

Parameters:

start=name: Name of graphics monitor to start
stop=name: Name of graphics monitor to stop
select=name: Name of graphics monitor to select
unlock=name: Name of graphics monitor to unlock
nlev=value: Number of color levels for each R/G/B (default: nlev=32: 32768 colors)

When the user enters the command d.mon without specifying parameter values, the below menu appears on the screen:

                        MONITOR MENU
Making sure that the graphics monitor is running:

  1      - Start a graphics monitor
         (also automatically selects this monitor)
  2      - Stop a graphics monitor

Choosing a graphics monitor for your graphics:

  3      - Select a graphics device for output
         (currently selected monitor:  name)
  4      - Release control of the graphics driver
         (let someone else use it)
         (option 4 appears only after selection of a monitor)

RETURN   quit

These parameters perform the following functions:

Start a Monitor.
In order to display on-screen GRASS graphics, the user must start and select a graphics monitor. By default, the start command actually runs two commands, to both start and select whatever monitor is named by the user. (The user can get a list of available monitors by setting the -l or -L flag on the command line.)
When a monitor is started, it is therefore also (automatically) selected for output, unless the -s flag is set by the user; the user can also explictly select a monitor that has been started (see (3) below). After a monitor is started, a blank graphics frame should appear on whatever terminal the user is using to display graphics.
The desired monitor should be started once and need not be restarted unless it is stopped (option 2) for some reason. A monitor may continue to run for any length of time, even when no GRASS session is being run. The monitor program runs in the background.
Using the nlev parameter the user can define the number of color levels to be used. nlev can be a value between 1 and 256. nlev=256 means 8bit for each R, G, B color channel equal to 24bit truecolor (16.7 million colors). The calculation of number of colors (ncolors) is performed by calculating:
```
 ncolors = nlev^3
```
Starting a monitor with a high number of colors may take some time to allocate the required memory.
Stop a Monitor.
Sometimes the monitor program needs to be stopped (terminated). Choosing option 2 will terminate a user-specified monitor program. A graphics monitor has two different types of status: monitor program not running, and monitor running. A monitor that has been started and/or selected will be listed as running; a monitor that has been stopped (or not started) will be listed as not running. The -L (list status) flag will list the status of each monitor connected to the system.
Select a Monitor.
When the user starts a monitor, it is also (automatically) selected for graphics output unless the user sets the -s flag. In order to use (direct graphics output to) a monitor, the user must select that monitor for use, either by simply starting the monitor without the -s flag or by explictly selecting the monitor for output using option 3. Only running monitors can be selected for graphics output. Once the user has selected a monitor for output, no other user can use this monitor for graphics output until the monitor driver is either released (by the user) or unlocked (by any user on the system).
The user can run multiple graphics monitors by simply starting each of the graphics monitors drivers he wishes to direct output to.
Release a Monitor.
Once a user has selected a monitor for graphics output, it is locked for use by that user until either: (1) the user voluntarily releases control of the monitor for use by another (option 4), or (2) another GRASS user unlocks the user's control of the monitor. Menu option 4 appears only to the person who has selected the monitor (since only that user can release control of his selected graphics monitor.) If another user wishes to unlock the user's control of the monitor, that user must run d.mon from the command line and set the unlock=name parameter.

You may choose multiple options within the d.mon program. To leave (exit) the d.mon menu, press the <RETURN> key.

NOTES

The d.mon program can regulate control of graphics monitors both in systems using multiple monitors and in systems using a single graphics monitor.

AUTHOR

Michael Shapiro, U.S. Army Construction Engineering Research Laboratory,
Full 24bit support by Roberto Flor, ITC-Irst, Trento, Italy