Simulate mouse click in background window

Question

I'm trying to use SendMessage to post mouse clicks to a background window (Chrome), which works fine, but brings the window to front after every click. Is there any way to avoid that?

Before anyone says this is a duplicate question, please make sure that the other topic actually mentions not activating the target window, because I couldn't find any.

Update: aha, hiding the window does the trick, almost. It receives simulated mouse/keyboard events as intended, and doesn't show up on screen. However, I can just barely use my own mouse to navigate around the computer, and keyboard input is completely disrupted.

So my question is, how does sending messages to a window affect other applications? Since I'm not actually simulating mouse/keyboard events, shouldn't the other windows be completely oblivious to this? Is it possibly related to the window calling SetCapture when it receives WM_LBUTTONDOWN ? And how would I avoid that, other than hooking the API call (which would be very, very ugly for such a small task)?

Answer 1

The default handling provided by the system (via DefWindowProc ) causes windows to come to the front (when clicked on) as a response to the WM_MOUSEACTIVATE message, not WM_LBUTTONDOWN .

The fact that Chrome comes to the front in response to WM_LBUTTONDOWN suggests that it's something Chrome is specifically doing, rather than default system behaviour that you might be able to prevent in some way.

The source code to Chrome is available; I suggest you have a look at it and see if it is indeed something Chrome is doing itself. If so, the only practical way you would be able to prevent it (short of compiling your own version of Chrome) is to inject code into Chrome's process and sub-class its main window procedure.