C / C++ / MFC

19-Dec-02 18:37

hi guys, I want to be able to detect mouse click on the desktop(not just any particular application window) Smile | :)

, how do I do that? any sample code/suggestion is appreciated

Taka Muraoka19-Dec-02 18:51

19-Dec-02 18:51

SetWindowsHookEx() with WH_MOUSE is probably what you want.

he he he. I like it in the kitchen! - Marc Clifton (on taking the heat when being flamed)

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king_of_the_world19-Dec-02 19:08

19-Dec-02 19:08

would you elaborate on it a little? sorry I'm a bit new to windows programming

thanks

Taka Muraoka19-Dec-02 19:12

19-Dec-02 19:12

Have a look in the MSDN.

You call SetWindowsHookEx() with a pointer to a function that you supply. Windows will then call this function every time something mouse-related happens, giving you the HWND that the event is for, where the mouse is on screen, etc.

Since there may be more than one program listening for these mouse events, you need to make sure that you pass the event on, by calling CallNextHookEx().

he he he. I like it in the kitchen! - Marc Clifton (on taking the heat when being flamed)

Awasu v0.4a[^]: A free RSS reader with support for Code Project.

king_of_the_world20-Dec-02 1:15

20-Dec-02 1:15

thanks for the pointer, now I still have some problem of getting it to work,
I have the following callback procedure that tries to show the mouse position

LRESULT CALLBACK MouseProc(int nCode, WPARAM wParam, LPARAM lparam){
MOUSEHOOKSTRUCT* mousehook=(MOUSEHOOKSTRUCT*)lparam;
POINT p=mousehook->pt;
char temp[20];
sprintf(temp,"mouse position is %d %d",p.x,p.y);
MessageBox(hWnd,temp,"",MB_OK);
return 0;
}

and I did SetWindowsHookEx(WH_MOUSE, 0,hInstance,0); but MouseProc was never been called for some reason, what did I do wrong, the following is my code in detail:

int PASCAL WinMain(HINSTANCE hInstance, HINSTANCE hPrev, LPSTR lpCmdLine, int Cmd) {

MSG msg;

// Setup and register the window class;

WNDCLASS wClass;
wClass.style =CS_HREDRAW|CS_VREDRAW;
wClass.lpfnWndProc =WindowProcedure; // callback-function;
wClass.cbClsExtra =0;
wClass.cbWndExtra =0;
wClass.hInstance =hInstance;
wClass.hIcon =LoadIcon(hInstance,IDI_APPLICATION);
wClass.hCursor =LoadCursor(NULL,IDC_ARROW);
wClass.hbrBackground =(HBRUSH)(COLOR_WINDOW+3);
wClass.lpszMenuName =NULL;
wClass.lpszClassName =WINDOWNAME;

RegisterClass(&wClass);

// Create the window and store the handle;

hWnd = CreateWindow(WINDOWNAME, // class name;
WINDOWNAME, // window name;
WS_OVERLAPPEDWINDOW, // window style;
CW_USEDEFAULT, CW_USEDEFAULT, // starting position (x,y);
320, 240, // width and height;
NULL, // parent handle;
NULL, // menu handle;
hInstance, // instance handle;
NULL); // other parameters;

// Check if window creation failed; otherwise show and update;

if(hWnd==NULL) return FALSE;
else {

ShowWindow (hWnd, Cmd);
UpdateWindow(hWnd);
}

HOOKPROC hookproc;
//static HINSTANCE hinstDLL;
static HHOOK hhook;

SetWindowsHookEx(WH_MOUSE, 0,hInstance,0);

// Message loop;

while(GetMessage(&msg,NULL,0,0)) {
TranslateMessage(&msg);
DispatchMessage (&msg);
}
return msg.wParam;
}

Taka Muraoka20-Dec-02 1:28

20-Dec-02 1:28

I was actually playing with this stuff the other day and couldn't get it work like this either Smile | :)

I had to pass in the current thread ID when setting the hook i.e. call GetCurrentThreadId(). So it should work OK as long as everything is in the one thread, which it is for me. If you really want a global hook or for this work for multiple threads, you're on your own!

BTW, I wouldn't call MessageBox() inside your hook procedure. This function is going to get called a *lot*, from deep inside Windows, and it's probably not going to like you trying to display a dialog box. Log it to a file instead,

he he he. I like it in the kitchen! - Marc Clifton (on taking the heat when being flamed)

Awasu v0.4a[^]: A free RSS reader with support for Code Project.

king_of_the_world20-Dec-02 1:38

20-Dec-02 1:38

thanks, that worked, but now I have a seg fault due to the HHOOK i m passing to SetWIndowsHookEx, the following is what I have, I simply create a new HHOOK, is this wrong?
what is the HHOOK for? I read the msdn doc on it but still kind of fuzzy, thanks.

static HHOOK hhook;

SetWindowsHookEx(WH_MOUSE, hookproc,hInstance,GetCurrentThreadId());

king_of_the_world20-Dec-02 1:40

20-Dec-02 1:40

sorry a correct to my previous post, when I say HHOOK, I meant HOOKPROC

Taka Muraoka20-Dec-02 1:50

20-Dec-02 1:50

Go back and read my original post. The crash is probably happening because you're not calling CallNextHookEx().

he he he. I like it in the kitchen! - Marc Clifton (on taking the heat when being flamed)

Awasu v0.4a[^]: A free RSS reader with support for Code Project.

king_of_the_world20-Dec-02 1:55

20-Dec-02 1:55

I put CallNextHookEx(0,nCode,wParam,lparam); in my callback function MouseProc, but it still crashed. Actually how do I obtain the first argument to CallNextBookEx inside MouseProc, the first argument is a handle to the current hook?
thanks

Taka Muraoka20-Dec-02 2:08

20-Dec-02 2:08

Since there may be more than 1 program wanting to receive these events, Windows keeps a list of everyone who is interested in receiving them. When you register for these events by calling SetWindowsHookEx(), the return value is a handle for the next person in the list. This is what you pass into CallNextHookEx() so that Windows can let him know about the event as well. He is then responsible for passing it on to the next guy and so on until everyone has received the event.

he he he. I like it in the kitchen! - Marc Clifton (on taking the heat when being flamed)

Awasu v0.4a[^]: A free RSS reader with support for Code Project.

king_of_the_world20-Dec-02 2:14

20-Dec-02 2:14

yes, my question was how to obtain the HOOKPROC that points to the current hookproc in my callback function in order to pass it to CallNextHookEx

CallNextHookEx(currentHookProc,nCode,wParam,lparam);
thanks