Add compatibility for glib>=2.62 (replace GTimeVal by GDateTime)

[amotl]

Hi again,

while working on sigrokproject/sigrok-meter#1, when building on macOS Catalina with glib installed through Homebrew, there is already glib 2.66.7.

However, GTimeVal has been deprecated since glib 2.62 and should be replaced by GDateTime [1], see also [2].

GTimeVal has been deprecated since version 2.62 and should not be used in newly-written code. Use GDateTime or guint64 instead.

So, this is just a humble attempt to make things work again on this end. As I told you in #122, I am not deeply involved into C/C++, but this update makes things work for us so you might want to build upon it in one of the future iterations.

With kind regards,
Andreas.

[1] https://developer.gnome.org/glib/stable/glib-Date-and-Time-Functions.html#GTimeVal
[2] https://tecnocode.co.uk/2019/08/24/gtimeval-deprecation-in-glib-2-61-2/

[amotl]

On macOS/Homebrew, glibmm is named differently.

$ pkg-config --list-all | grep glib
gio-unix-2.0                        GIO unix specific APIs - unix specific headers for glib I/O library
gio-2.0                             GIO - glib I/O library
glib-2.0                            GLib - C Utility Library
glibmm-2.68                         glibmm - C++ wrapper for GLib

[amotl]

... build upon it in one of the future iterations.

While the current implementation within this patch works for me, I am not sure if it will produce a memleak.

GDateTime is reference counted: the reference count is increased by calling g_date_time_ref() and decreased by calling g_date_time_unref(). When the reference count drops to 0, the resources allocated by the GDateTime structure are released [1].

You should release the return value by calling GLib.DateTime.unref() when you are done with it [2].

---

On the other hand, when already refactoring something related to timekeeping, using the monotonic clock might also be an option [3,4]?

[1] https://developer.gnome.org/glib/stable/glib-GDateTime.html
[2] https://lazka.github.io/pgi-docs/GLib-2.0/classes/DateTime.html#GLib.DateTime.new
[3] https://stackoverflow.com/questions/41894213/what-is-the-use-of-clock-realtime
[4] https://stackoverflow.com/questions/3523442/difference-between-clock-realtime-and-clock-monotonic

[depili]

Implemented in e446b3c and ee9e086

[amotl]

Dear @depili and @gsigh,

thank you very much.

With kind regards,
Andreas.