Windows下C++通过hook捕捉鼠标

/*
 *  Make sure project type is windows application
 */
 
#define _WIN32_WINNT 0x0500
#include<windows.h>
#include<cmath>
 
LRESULT CALLBACK mouseHookProc(int nCode,WPARAM wParam,LPARAM lParam) {
   // Get event information
   PMSLLHOOKSTRUCT p = (PMSLLHOOKSTRUCT) lParam;
 
   bool eat = false;
 
   // Screen resolution
   static float screen_cx = static_cast<float>( GetSystemMetrics(SM_CXSCREEN) );
   static float screen_cy = static_cast<float>( GetSystemMetrics(SM_CYSCREEN) );
 
   // Centre of screen
   static float screen_centre_x = screen_cx / 2.0f;
   static float screen_centre_y = screen_cy / 2.0f;
 
   // Calculate distance away from centre of screen
   float dx = p->pt.x - screen_centre_x;
   float dy = p->pt.y - screen_centre_y;
 
   float dist = sqrt(dx * dx + dy * dy);
 
   // Check if cursor is more than 300px away from centre of screen
   if (dist > 300) {
      float angle = atan2(dy,dx);
 
      // Trap cursor
      SetCursorPos(
         /* X */ int( screen_centre_x + cos(angle) * 300 ),/* Y */ int( screen_centre_y + sin(angle) * 300 )
      );
 
      // Stop windows handling event
      eat = true;
   }
 
   return (eat ? 1 : CallNextHookEx(NULL,nCode,wParam,lParam));
}
 
int WINAPI WinMain(HINSTANCE hInstance,HINSTANCE hPrevInstance,LPSTR lpCmdLine,int nShowCmd) {
 
   // Set mouse hook
   HHOOK mouseHook = SetWindowsHookEx(
                  WH_MOUSE_LL,/* Type of hook */
                  mouseHookProc,/* Hook process */
                  hInstance,/* Instance */
                  NULL);
 
   // Wait for user to exit
   MessageBox(NULL,"Press OK to close.","",MB_OK);
   return 0;
}