timeSetTimer Callback Issues

[eeboy]

I have a compilation error I can't figure out. I am calling timeSetTimer from a member function within a class. The callback function is also a member of the class.

When I compile this statement:

timeSetEvent(iDelay, 0, &wait, NULL, TIME_ONESHOT);

I get:

error C2276: '&' : illegal operation on bound member function expression

When I compile this statement:

timeSetEvent(iDelay, 0, &FOO::wait, NULL, TIME_ONESHOT);

I get:

error C2664: 'timeSetEvent' : cannot convert parameter 3 from 'void (__stdcall FOO::*)(unsigned int,unsigned int,unsigned long,unsigned long,unsigned long)' to 'void (__stdcall *)(unsigned

Any ideas?

Thanks!

[Andreas Masur]

How to use class member functions as callbacks?

[eeboy]

Makes sense... Thanks!

[Andreas Masur]

You are welcome...

[eeboy]

Ok... I am back with a similar issue. I've decided to place a flag in the callback function that I will clear upon execution. I have the flag as a private member of the class. When I attempt to clear it inside the callback function with:

pulsing=false;

I get:

illegal reference to data member 'FOO:ulsing' in a static member function

The error makes sense because the this pointer is not passed along. I figured declaring the flag as

static bool pulsing;

would solve this issue... but that generates an unresolved external symbol.

Any help?

[Andreas Masur]

You basically have two choices here...

• Using a static member. They need to be defined however, thus...
  

  // .hpp
  class foo
  {
    static bool pulsing;
  };
  
  // .cpp
  bool foo::pulsing = false;

• 'timeSetEvent()' allows you to pass a user-defined value as a 'DWORD_PTR'. You can use this to pass the 'this' pointer of the class instance you want to access in your callback...

[eeboy]

I ended up using the DWORD dwUser parm to pass the pointer this to the function. I couldn't get your first example to work. I had actually tried that. It doesn't seem to like the static bool pulsing declaration. I still get the unresolved external symbol error.

Even though I have it working I would still like to know why declaring the flag as static doesn't work for me.

Thanks!

[Andreas Masur]

Even though I have it working I would still like to know why declaring the flag as static doesn't work for me.

Well...without seeing the actual you tried it with, it is pretty hard to tell...nevertheless, it should have worked.