Re: SetTimer() & callback handler
SetTimer was written way back when the Windows World was young, and C++ hadn't yet swept the world
to become the de facto standard language for Windows programming.
Using a TimerProc or WM_TIMER message is an either/or choice.
The TimerProc cannot be an instance-specific class method, as that would require an implied 'this'
pointer to be passed when calling the function, and how could Windows know which instance to use?
It must be a non-class function or a class static method.
When the btn_timer is called, you must use some other means to determine which class instance of
MomPC to use. Generally, globals are considered "evil", but occasionally have legitimate uses when
done correctly. What criterion should be used to associate a timer callback with a MomPC instance?
"kevin_waite" <kevin001.waite@gmail.com> wrote in message
news:36fe214b-c7f9-45c3-a0e8-69896c62f8fd@y7g2000yqa.googlegroups.com...
Newbie here, I need some help/guidance with the
following:
My main class is MomPC
I have a static non-class CALLBACK hander called: btn_timer()
btn_timer() is defined identically to TIMERPROC
I can use SetTimer() successfully with the static btn_timer()
as the 4th parm/CALLBACK to SetTimer().
However, when the handler runs (timer expired) btn_timer()
runs but does not have access to my main class instance
of MomPC -- booooooo.
If I make btn_timer() as a method with MomPC -- then I do
not know how to cast &MomPC::btn_timer() into (TIMERPROC)
successfully -- this may be impossible -- I just do not know.
If this can be done -- this would likely solve my problem.
The common solution to getting the callback handler to get
access to a class is to define the event handler and callback
handler initialization is to define a user pionter and pass "this"
during
the setup --- SetTimer doesn't have a user pointer parameter
to use for this purpose....... I can only think to add one global
as a pointer to my main class -- surely there is a better way,
no?
When there is a timer callback set for timer expirations --
will SetTimer() also be putting WM_TIMER
message in the window's message box? I mean, does having
the callback handler inplace remove the WM_TIMER
messages -- this is an either/or?
Thanks in advance.
Sincerely,
Kevin Waite