winapi - c++: How to catch mouse clicks wherever they happen

Question

I am stuck with an application I am writing where I need to monitor for mouse clicks.

The clicks may happen anywhere on the screen and not inside the app window, and for each click I must pass a message (perform an action or something).

I looked around and read some suggestions like using

LRESULT CALLBACK WndProc(HWND hWnd, UINT message, WPARAM wParam, LPARAM lParam)

but I was unsuccessful.

Does anyone have an idea on how to implement what I need?

Answer 1

You need to set a mouse hook as described in MSDN.

Note that in your case the hook would need to be global. This means that you need to implement a handler function in a DLL, which will be loaded into all processes in the system which receive mouse message. Such DLL will communicate with your main application using some interprocess communication (IPC) mechanism like shared memory or via Windows messages posted (not sent) from the DLL to the main application.

You can use the source code from this CodeProject article as a guide.

Update: as per Chris' correction, I should note that above applies to "regular" mouse hook which is synchronous. Low-level hook doesn't need to be located in the DLL, but it has certain limitations which are described in the corresponding MSDN article.