In C++20, QDateTime is a direct equivalent of a sys_time<milliseconds>
time point. (Before, it might not have been, because system_clock before
C++20 was not guaranteed to be tracking Unix time, AKA UTC time without
leap seconds.) To be specific, sys_time<milliseconds> corresponds to
a QDateTime using the Qt::UTC timespec.
This patch:
1) adds named constructors taking time_points:
* a generic one taking any time_point convertible (via clock_cast) to
a system_clock (this obviously includes system_clock, but also e.g.
utc_clock)
* another couple taking local_time, interpreted as a duration from
1/1/1970 in local time.
2) adds a named constructor from zoned_time (i.e. a sys_time + a
timezone), that we can easily support via QTimeZone.
3) add conversion functions towards sys_time, matching the existing
to(M)SecsSinceEpoch() functions.
[ChangeLog][QtCore][QDateTime] QDateTime can now be constructed
from std::chrono::time_point objects (including local_time), as
well as from std::chrono::zoned_time objects. Moreover, they
can be converted to std::chrono::time_point using system_clock
as their clock.
Change-Id: Ic6409bde43bc3e745d9df6257e0a77157472352d
Reviewed-by: Thiago Macieira <thiago.macieira@intel.com>
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