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# -*- coding: utf-8 -*-
# -----------------------------------------------------------------------------
# Copyright (c) Vispy Development Team. All Rights Reserved.
# Distributed under the (new) BSD License. See LICENSE.txt for more info.
# -----------------------------------------------------------------------------
import os
import re
from subprocess import CalledProcessError
from ..logs import logger
from ..wrappers import run_subprocess
def _get_dpi_from(cmd, pattern, func):
"""Match pattern against the output of func, passing the results as
floats to func. If anything fails, return None.
"""
try:
out, _ = run_subprocess([cmd])
except (OSError, CalledProcessError):
pass
else:
match = re.search(pattern, out)
if match:
return func(*map(float, match.groups()))
def _xrandr_calc(x_px, y_px, x_mm, y_mm):
if x_mm == 0 or y_mm == 0:
logger.warning("'xrandr' output has screen dimension of 0mm, " +
"can't compute proper DPI")
return 96.
return 25.4 * (x_px / x_mm + y_px / y_mm) / 2
def get_dpi(raise_error=True):
"""Get screen DPI from the OS
Parameters
----------
raise_error : bool
If True, raise an error if DPI could not be determined.
Returns
-------
dpi : float
Dots per inch of the primary screen.
"""
# If we are running without an X server (e.g. OSMesa), use a fixed DPI
if 'DISPLAY' not in os.environ:
return 96.
from_xdpyinfo = _get_dpi_from(
'xdpyinfo', r'(\d+)x(\d+) dots per inch',
lambda x_dpi, y_dpi: (x_dpi + y_dpi) / 2)
if from_xdpyinfo is not None:
return from_xdpyinfo
from_xrandr = _get_dpi_from(
'xrandr', r'(\d+)x(\d+).*?(\d+)mm x (\d+)mm',
_xrandr_calc)
if from_xrandr is not None:
return from_xrandr
if raise_error:
raise RuntimeError('could not determine DPI')
else:
logger.warning('could not determine DPI')
return 96
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