/*   *  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;  }