# coding: utf-8
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"""This module provides convenient functions related to Qt.
"""

__authors__ = ["V. Valls"]
__license__ = "MIT"
__date__ = "30/11/2016"


from . import _qt


def supportedImageFormats():
    """Return a set of string of file format extensions supported by the
    Qt runtime."""
    if _qt.BINDING == 'PySide2':
        def convert(data):
            return str(data.data(), 'ascii')
    else:
        convert = lambda data: str(data, 'ascii')
    formats = _qt.QImageReader.supportedImageFormats()
    return set([convert(data) for data in formats])


__globalThreadPoolInstance = None
"""Store the own silx global thread pool"""


def silxGlobalThreadPool():
    """"Manage an own QThreadPool to avoid issue on Qt5 Windows with the
    default Qt global thread pool.

    A thread pool is create in lazy loading. With a maximum of 4 threads.
    Else `qt.Thread.idealThreadCount()` is used.

    :rtype: qt.QThreadPool
    """
    global __globalThreadPoolInstance
    if __globalThreadPoolInstance is  None:
        tp = _qt.QThreadPool()
        # Setting maxThreadCount fixes a segfault with PyQt 5.9.1 on Windows
        maxThreadCount = min(4, tp.maxThreadCount())
        tp.setMaxThreadCount(maxThreadCount)
        __globalThreadPoolInstance = tp
    return __globalThreadPoolInstance
