c++ - Function to check if a window is visible on screen does not work on Windows 7 -

for program, need know if @ least pixel of window visible on screen.

i'm using code:

bool iswindowvisible(hwnd hwnd) {     rect r1;     getwindowrect(hwnd, &r1);     hrgn x = createrectrgnindirect(&r1);      hwnd s = gettopwindow(0);      {         if (iswindowvisible(s)) {             rect r2;             getwindowrect(s, &r2);             hrgn y = createrectrgnindirect(&r2);              int res = combinergn(x, x, y, rgn_diff);             deleteobject(y);             if (res == nullregion) {                 deleteobject(x);                 return false;             }         }     } while ((s = getnextwindow(s, gw_hwndnext)) && s != hwnd);      deleteobject(x);     return true; } 

this work on windows 8.1 , windows 10, not on windows 7. on windows 7, returns false every time.

i thought because of aero effects, when disable it, still happens. got method here on stackoverflow , adapted c++.

does know why happening?

ok, figured out myself. not check if window on top of z-order same window 1 check. if window still on top, function subtracts , returns false. don't know why error happens on windows 7, @ least fixed now.