I create a Windows timer using the following
FHandle := SetTimer(0, 0, 1000, TFNTimerProc(@TMyClass.MyMethod));
Is this thread shown in the Delphi "Threads" window. If Yes how I can get this Thread ID?
views:
174answers:
2
+3
A:
SetTimerdoes not create a thread but does call the specified function in the context of the main thread after the specified timeout. If you don't pass a callback function, SetTimer posts a WM_TIMER message to your main window class.
See the MSDN reference for SetTimer for more information.
Smasher
2010-01-18 15:59:54
+5
A:
There is no thread created by that function. The OS calls the callback function when your program handles the wm_Timer message. It's called from within the context of the same thread that called SetTimer, so the thread had better have a message pump. (It you're calling this from the main VCL thread, then the message pump is provided for you by the TApplication class.)
Furthermore, SetTimer doesn't return a handle. It returns a timer ID.
And finally, unless that method is a class static method, it won't work the way you hope. If the signature of the callback matches what SetTimer expects you to provide, you won't need a type cast, so if you needed to type-cast the function pointer to make the compiler accept your code, you probably got it wrong.
Rob Kennedy
2010-01-18 16:00:43
+1 because you spent a minute more than I did and wrote a very complete answer :)
Smasher
2010-01-18 16:06:03
Yep, good answer apart from the nitpick about whether an "ID" is a "handle". Some handles *are* just IDs, some handles are pointers. Making the distinction is likely to raise unnecessary questions about how IDs should be handled [sic] differently from handles.
Deltics
2010-01-18 19:35:41
Not all handles are IDs, and not all IDs are handles. Conflating the two hinders communication. If you tell people you have a "timer handle," they're liable to think you're talking about a waitable timer, which isn't the same thing at all. Thinking of a timer event ID as a handle might tempt you to call handle-related functions on it, like DuplicateHandle or CloseHandle, but that's not allowed. If the documentation calls something an ID, then call it an ID.
Rob Kennedy
2010-01-18 20:18:01