pyvirtualdisplay is a python wrapper for [Xvfb][1], [Xephyr][2] and [Xvnc][3]
Links:
* home: https://github.com/ponty/pyvirtualdisplay
* PYPI: https://pypi.python.org/pypi/pyvirtualdisplay
[](https://travis-ci.org/ponty/pyvirtualdisplay)
Features:
- python wrapper
- supported python versions: 3.6, 3.7, 3.8, 3.9
- back-ends: [Xvfb][1], [Xephyr][2] and [Xvnc][3]
Possible applications:
* headless run
* GUI testing
* automatic GUI screenshot
Installation
============
install the program:
```console
$ python3 -m pip install pyvirtualdisplay
```
optional: [Pillow][pillow] should be installed for ``smartdisplay`` submodule:
```console
$ python3 -m pip install pillow
```
If you get this error message on Linux then your Pillow version is old.
```
ImportError: ImageGrab is macOS and Windows only
```
on Ubuntu 20.04:
```console
$ sudo apt-get install xvfb xserver-xephyr tigervnc-standalone-server xfonts-base
$ python3 -m pip install pyvirtualdisplay pillow
```
Usage
=====
Controlling the display with `start()` and `stop()` methods:
```py
from pyvirtualdisplay import Display
disp = Display()
disp.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:
```py
from pyvirtualdisplay import Display
with Display() as disp:
# display is active
pass
# display is stopped
```
Selecting Xvfb backend:
```py
disp=Display()
# or
disp=Display(visible=False)
# or
disp=Display(backend="xvfb")
```
Selecting Xephyr backend:
```py
disp=Display(visible=True)
# or
disp=Display(backend="xephyr")
```
Selecting Xvnc backend:
```py
disp=Display(backend="xvnc")
```
Setting display size:
```py
disp=Display(size=(100, 60))
```
Setting display color depth:
```py
disp=Display(color_depth=24)
```
Headless run
------------
The display is hidden.
```py
# 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()
```
If `visible=True` then a nested Xephyr window opens and the GUI can be controlled.
vncserver
---------
The same as headless example, but it can be controlled with a VNC client.
```py
# 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:
```console
$ python3 -m pyvirtualdisplay.examples.vncserver
```
<!-- embedme doc/gen/vncviewer_localhost:5904.txt -->
Check it with vncviewer:
```console
$ vncviewer localhost:5904
```
GUI Test
--------
```py
# 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()
```
<!-- embedme doc/gen/python3_-m_pyvirtualdisplay.examples.lowres.txt -->
Run it:
```console
$ python3 -m pyvirtualdisplay.examples.lowres
```
Image:
Screenshot
----------
```py
# 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")
```
<!-- embedme doc/gen/python3_-m_pyvirtualdisplay.examples.screenshot.txt -->
Run it:
```console
$ python3 -m pyvirtualdisplay.examples.screenshot
```
Image:
Nested Xephyr
-------------
```py
# 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()
```
<!-- embedme doc/gen/python3_-m_pyvirtualdisplay.examples.nested.txt -->
Run it:
```console
$ 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
===========
If more X servers are started at the same time then there is race for free display numbers.
_"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/
Version 1.13 was released in 2012: https://www.x.org/releases/individual/xserver/
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 to choose the display number.
If not then a free display number is generated and there are 10 retries by default
which should be enough for starting 10 X servers at the same time.
`displayfd` usage is disabled on macOS because it doesn't work with XQuartz-2.7.11, always 0 is returned.
Thread safety
=============
All previous examples are not thread-safe, because `pyvirtualdisplay` replaces `$DISPLAY` environment variable in global [`os.environ`][environ] in `start()` and sets back to original value in `stop()`.
To make it thread-safe you have to manage the `$DISPLAY` variable.
Set `manage_global_env` to `False` in constructor.
```py
# pyvirtualdisplay/examples/threadsafe.py
"Start Xvfb server. Open xmessage window. Thread safe."
from easyprocess import EasyProcess
from pyvirtualdisplay import Display
# manage_global_env=False is thread safe
with Display(manage_global_env=False) as disp:
# disp.new_display_var should be used for new processes
print("disp.new_display_var=" + disp.new_display_var)
# disp.env() copies global os.environ and adds disp.new_display_var
print("disp.env()['DISPLAY']=" + disp.env()["DISPLAY"])
# set $DISPLAY for subprocesses
with EasyProcess(["xmessage", "-timeout", "1", "hello"], env=disp.env()) as proc:
proc.wait()
```
<!-- embedme doc/gen/python3_-m_pyvirtualdisplay.examples.threadsafe.txt -->
Run it:
```console
$ python3 -m pyvirtualdisplay.examples.threadsafe
disp.new_display_var=:2
disp.env()['DISPLAY']=:2
```
Hierarchy
=========
[1]: http://en.wikipedia.org/wiki/Xvfb
[2]: http://en.wikipedia.org/wiki/Xephyr
[3]: https://tigervnc.org/
[pillow]: https://pillow.readthedocs.io
[environ]: https://docs.python.org/3/library/os.html#os.environ