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I would like to add a hook to an application. I am using SetWindowsHookEx and I can create a system wide hook, but I want to create a hook for a particular application. I need to have thread id of the target application to hook it. I know title of the window, I know exe name and from these I can get window handle and process id, but how do I get the thread id? I saw a post about how to do it in c#, but I do not see how to get a list of threads in c++.
HWND windowHandle = FindWindow(NULL, _T("SomeOtherApp"));
DWORD processId = GetWindowThreadProcessId(windowHandle, NULL);
DWORD threadId = ??? // How do I get thread id here?
HHOOK hook = ::SetWindowsHookEx( WH_CBT, HookCBTProc, hInst, threadId);
Thanks, Alexander.
471
The thread ID of the initial (main) thread is the same as the process ID of the entire process. Thread IDs for subsequently created threads are distinct. They are allocated from the same numbering space as process IDs. Process IDs and thread IDs are sometimes also referred to collectively as task IDs.
If you have a thread identifier, you can get the thread handle by calling the OpenThread function. OpenThread enables you to specify the handle's access rights and whether it can be inherited. A thread can use the GetCurrentThread function to retrieve a pseudo handle to its own thread object.
Identifying the thread On Unix® and Linux® systems, you can use the top command: $ top -n 1 -H -p [pid]replacing [pid] with the process ID of the affected process. On Solaris®, you can use the prstat command: $ prstat -L -p [pid]replacing [pid] with the process ID of the affected process.
Threads are the basic unit to which an operating system allocates processor time. A thread is code that is to be serially executed within a process and more than one thread can be executing code inside a process.
GetWindowThreadProcessId() returns the thread ID. You are erroneously assigning the thread ID to the process ID variable. Instead write:
HWND windowHandle = FindWindow(NULL, _T("SomeOtherApp"));
DWORD threadId = GetWindowThreadProcessId(windowHandle, NULL);
HHOOK hook = ::SetWindowsHookEx(WH_CBT, HookCBTProc, hInst, threadId);
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