## Display drivers

The current command line rendering mechanism is direct rendering into a file. The driver is selected by setting the `GRASS_RENDER_IMMEDIATE` variable or by running d.mon module.

List of available display drivers:

- Cairo driver
- PNG driver
- PS driver (Postscript)
- HTMLMAP driver

## NOTES

### GRASS_RENDER_COMMAND

If environmental variable GRASS_RENDER_COMMAND is defined, rendering is redirected by display library to the given external command defined by this variable. Currently only Python scrips are supported.

Lets start with simple example of Python script called render.py:

    #!/usr/bin/env python3

    import os
    import sys

    import grass.script as grass
    from grass.script import task as gtask

    os.environ['GRASS_RENDER_IMMEDIATE'] = 'default'
    os.environ['GRASS_RENDER_FILE'] = 'output.png'

    cmd, dcmd = gtask.cmdstring_to_tuple(sys.argv[1])

    grass.run_command('d.text', text="Test of GRASS_RENDER_COMMAND redirection")

    os.environ['GRASS_RENDER_FILE_READ'] = 'TRUE'
    grass.run_command(cmd, **dcmd)

After defining GRASS_RENDER_COMMAND variable (example for Bash):

    export GRASS_RENDER_COMMAND=render.py

Display GRASS modules like d.rast or d.vect will be executed by render.py program. For example the command

    d.vect roadsmajor

produces output PNG file output.png which will contain rendered features from vector map roadsmajor and sample text "Test of GRASS_RENDER_COMMAND redirection".

## SEE ALSO

d.mon, variables

## SOURCE CODE

Available at: Display drivers source code (history)

Latest change: Sun Oct 3 04:25:57 2021 in commit: 18b732a3cf8c8186bec13ed4728c5e30de95049a

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