当用户按下 Ctrl 并单击时获取鼠标坐标

Question

I want to get mouse click coordinates X and Y when user press Ctrl and click at same time. User may click anywhere on the screen or programs. I want my program to catch the event and get coordinates when Ctrl key is down pressed and mouse click occurs at same time. I want to get system coordinates X and Y, not the window coordinates of other programs. I'm using C++ .

How to do that ?

Windows OS, WIN API code

I'm doing next which is not working:

HHOOK MouseHook;
LRESULT CALLBACK MouseHookProc(int nCode, WPARAM wParam, LPARAM lParam){

        PKBDLLHOOKSTRUCT k = (PKBDLLHOOKSTRUCT)(lParam);
        POINT p;


        if(wParam == WM_RBUTTONDOWN)
        {
          // right button clicked
          GetCursorPos(&p);
          //p.x 
          //p.y
          //my program is never getting here, why ?
        }

}
 MouseHook = SetWindowsHookEx(WH_MOUSE_LL,(HOOKPROC)MouseHookProc,0,0);

if I change the above line to: MouseHook = SetWindowsHookEx(WH_MOUSE,(HOOKPROC)MouseHookProc,GetModuleHandle(NULL),0); then it will work only for my own program window, but not hooking clicks outside of my program

Answer 1

The way I would approach is I would create a global variable say

int ctrl_pressed = 0 
/* 
0 -- ctrl nt pressed
1 -- Crtl Pressed
*/

Step 1: Now I would handle both WM_KEYDOWN and WM_KEYUP for ctrl

Step 2: In the callback of WM_KEYDOWN (if lparam is ctrl ) I would set ctrl_pressed to 1. And in case of WM_KEYUP I would set ctrl_pressed to 0.

Step 3: Now Finally ill handle WM_MOUSECLICKED and then check if ctrl_pressed(global) is 1 , which if true I can just get the coordinates.

This is just an approach may be not the most efficient solution. Wait for more experienced WIN32 Developers to give their input on this.

Answer 2

Have you read this article? link

First of all, if you want to catch system entire mouse + keyboard event, your hooking function must be placed on a dll.

1)If nCode is less than zero, the hook procedure must return the value returned by CallNextHookEx. Like below,

if(nCode < 0)
{ 
   CallNextHookEx(hook, nCode, wParam, lParam);
   return 0;
} 

If CallNextHookEx is not called, there is a chance that other processes that have installed hook may not get the events correctly.

2)And then, check nCode again, whether it is HC_ACTION .

switch (nCode) 
{ 
  case HC_ACTION:
     ... 

3)Finally, you can check WPARAM for WM_RBUTTONDOWN , and LPARAM for MSLLHOOKSTRUCT