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Subject: Re: [std-proposals] Proposal : std::timer
From: Михаил Найденов (mihailnajdenov_at_[hidden])
Date: 2020-01-11 03:15:03


Note that these kind of timers are always tied to an event loop.
I am not sure it is good idea to have timer, that works outside the
event loop you presumably already have. In Your example you should use the
timer of "Framework".

On Sat, Jan 11, 2020 at 1:28 AM contact--- via Std-Proposals <
std-proposals_at_[hidden]> wrote:

> Hello,
>
> I hope you're well and you enjoy 2020. I'm writing you a short message
> about a C++ proposal. Of course, the C++ is my favorite programming
> language and I have an idea about a new std class or struct that doesn't
> yet exist. I think it could be cool to have a std::timer similar to the
> win32 timer (
> https://docs.microsoft.com/en-us/windows/win32/winmsg/using-timers) or
> the qt timer (https://doc.qt.io/qt-5/qtimer.html) or the GLUT timer (
> https://linux.die.net/man/3/gluttimerfunc) or ...
>
> The implementation can be discuted of course. It can use std::chrono,
> std::thread, std::function and more.
>
> This is a draft.
>
> namespace std
> {
> class timer
> {
> public:
>
> timer(); // constructor
>
> // ANOTHER VERSION OF THE CONSTRUCTORS : THE ADVANCED VERSION with which
> thread to use for the call of the callback
> timer(); // will call the callback on the main thread (or
> the thread where the timer has been constructed)
> timer(thread_id); // will use this thread_id for the call of
> the callback
>
> virtual ~timer(); // stop and destroy
>
> void start_once(function, when = 0); // will call the callback named
> function after a fixed duration
> void start_interval(function, interval_duration, nbTimes, when = 0);
> // will call the callback nb times every 'interval_duration' after a fixed
> duration
> void restart(); // stop the timer and call start_xxx with the
> last used params
> void stop(); // stop the timer but the restart can do
> something
> void cancel(); // stop the timer but the restart does
> nothing
> bool is_active() const; // start_xxx has_been used and the timer
> is still active
> bool can_restart() const; // restart can be used
> private:
> // ...
> };
> }
>
> I added 1 example :
>
> Example #1
>
> Sometime in UI developement (or in network), you need a timer. At the end
> of the timer (like a timeout), a callback will be called. This version
> helps to write less code and with an easy manner.
>
> I put a small example : You want to know when the user stopped to move the
> mouse.
>
> The pseudo c++ code is here :
>
> class MyMainWindow : public Framework::Window
> {
> public:
> MyMainWindow()
> {
> this->SetMouseMove(MyMainWindow::OnMouseMove); // set the event handler
>
> // set the timer to 3 seconds
> timer.start_once(MyMainWindow::DoTheAction, 3s);
> timer.stop(); // stop it now
> }
>
> static void OnMouseMove(...)
> {
> // reset the timer
> timer.restart(); // will call timer.stop() and timer.start_once() with
> the last used params
> }
>
> static void DoTheAction()
> {
> std::cout << "the user stopped to move the mouse since 3 secondes" <<
> std::endl;
> // ... do the other stuffs ...
> }
>
> private:
> std::timer timer;
> };
>
> Remark 1 : There are also another "Timer" that gives the elapsed time
> between a start/stop (used for benchmark) like the Boost Timer (
> https://www.boost.org/doc/libs/1_53_0/libs/timer/doc/index.html). Herb
> sent me this link. Thanks. We need to take in consideration the 'good
> naming' of course.
>
> Remark 2 : I don't yet talk about the implementation and the accuracy. I'm
> waiting that this proposal is accepted.
>
> What do you think ?
>
> BR,
> Mustapha
>
> --
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> Std-Proposals_at_[hidden]
> https://lists.isocpp.org/mailman/listinfo.cgi/std-proposals
>



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