bearzeng/pyvirtualdisplay

Python wrapper for Xvfb, Xephyr and Xvnc

pyvirtualdisplay is a python wrapper for Xvfb, Xephyr and Xvnc

Links:

• home: https://github.com/ponty/pyvirtualdisplay
• PYPI: https://pypi.python.org/pypi/pyvirtualdisplay

Features:

• python wrapper
• supported python versions: 2.7, 3.6, 3.7, 3.8
• back-ends: Xvfb, Xephyr and Xvnc

Possible applications:

• headless run
• GUI testing
• automatic GUI screenshot

Installation

install the program:

$ python3 -m pip install pyvirtualdisplay

optional: pyscreenshot and Pillow should be installed for smartdisplay submodule:

$ python3 -m pip install pyscreenshot pillow

on Ubuntu:

$ sudo apt-get install xvfb xserver-xephyr vnc4server xfonts-base
$ python3 -m pip install pyvirtualdisplay pyscreenshot pillow

Usage

Controlling the display with start() and stop() methods:

from pyvirtualdisplay import Display
disp = Display().start()
# display is active
disp.stop()
# display is stopped

After Xvfb display is activated "DISPLAY" environment variable is set for Xvfb. (e.g. os.environ["DISPLAY"] = :1) After Xvfb display is stopped "DISPLAY" environment variable is restored to its original value.

Controlling the display with context manager:

from pyvirtualdisplay import Display
with Display() as disp:
    # display is active
    pass
# display is stopped

Selecting Xvfb backend:

disp=Display()
# or
disp=Display(visible=False)
# or
disp=Display(backend="xvfb")

Selecting Xephyr backend:

disp=Display(visible=True)
# or
disp=Display(backend="xephyr")

Selecting Xvnc backend:

disp=Display(backend="xvnc")

Setting display size:

disp=Display(size=(100, 60))

Setting display color depth:

disp=Display(color_depth=24)

headless run

The display is hidden. If visible=True then a nested Xephyr window opens and the GUI can be controlled.

# pyvirtualdisplay/examples/headless.py

"Start Xvfb server. Open xmessage window."

from easyprocess import EasyProcess

from pyvirtualdisplay import Display

with Display(visible=False, size=(100, 60)) as disp:
    with EasyProcess(["xmessage", "hello"]) as proc:
        proc.wait()

vncserver

The same as headless example, but it can be controlled with a VNC client.

# pyvirtualdisplay/examples/vncserver.py

"Start virtual VNC server. Connect with: vncviewer localhost:5904"

from easyprocess import EasyProcess

from pyvirtualdisplay import Display

with Display(backend="xvnc", size=(100, 60), rfbport=5904) as disp:
    with EasyProcess(["xmessage", "hello"]) as proc:
        proc.wait()

Run it:

$ python3 -m pyvirtualdisplay.examples.vncserver

Check it with vncviewer:

$ vncviewer localhost:5904

GUI Test

# pyvirtualdisplay/examples/lowres.py

"Testing gnumeric on low resolution."
from easyprocess import EasyProcess

from pyvirtualdisplay import Display

# start Xephyr
with Display(visible=True, size=(320, 240)) as disp:
    # start Gnumeric
    with EasyProcess(["gnumeric"]) as proc:
        proc.wait()

Run it:

$ python3 -m pyvirtualdisplay.examples.lowres

Image:

Screenshot

# pyvirtualdisplay/examples/screenshot.py

"Create screenshot of xmessage in background using 'smartdisplay' submodule"
from easyprocess import EasyProcess

from pyvirtualdisplay.smartdisplay import SmartDisplay

# 'SmartDisplay' instead of 'Display'
# It has 'waitgrab()' method.
# It has more dependencies than Display.
with SmartDisplay() as disp:
    with EasyProcess(["xmessage", "hello"]):
        # wait until something is displayed on the virtual display (polling method)
        # and then take a fullscreen screenshot
        # and then crop it. Background is black.
        img = disp.waitgrab()
img.save("xmessage.png")

Run it:

$ python3 -m pyvirtualdisplay.examples.screenshot

Image:

Nested Xephyr

# pyvirtualdisplay/examples/nested.py

"Nested Xephyr servers"
from easyprocess import EasyProcess

from pyvirtualdisplay import Display

with Display(visible=True, size=(220, 180), bgcolor="black"):
    with Display(visible=True, size=(200, 160), bgcolor="white"):
        with Display(visible=True, size=(180, 140), bgcolor="black"):
            with Display(visible=True, size=(160, 120), bgcolor="white"):
                with Display(visible=True, size=(140, 100), bgcolor="black"):
                    with Display(visible=True, size=(120, 80), bgcolor="white"):
                        with Display(visible=True, size=(100, 60), bgcolor="black"):
                            with EasyProcess(["xmessage", "hello"]) as proc:
                                proc.wait()

Run it:

$ python3 -m pyvirtualdisplay.examples.nested

Image:

xauth

Some programs require a functional Xauthority file. PyVirtualDisplay can generate one and set the appropriate environment variables if you pass use_xauth=True to the Display constructor. Note however that this feature needs xauth installed, otherwise a pyvirtualdisplay.xauth.NotFoundError is raised.

Concurrency

"Recent X servers as of version 1.13 (Xvfb, too) support the -displayfd command line option: It will make the X server choose the display itself" https://stackoverflow.com/questions/2520704/find-a-free-x11-display-number/

First help text is checked (e.g. Xvfb -help) to find if -displayfd flag is available. If -displayfd flag is available then it is used, if not then there are 10 retries by default which should be enough for starting 10 concurrent X servers. The retries parameter can be increased if necessary.

Hierarchy