virt_screen.right  = GetSystemMetrics(SM_CXVIRTUALSCREEN);
virt_screen.bottom = GetSystemMetrics(SM_CYVIRTUALSCREEN);
OffsetRect(&virt_screen, GetSystemMetrics(SM_XVIRTUALSCREEN), GetSystemMetrics(SM_YVIRTUALSCREEN));

Mode (1600x1200): (-1600 0)x(1600 1200) monitors: [2][1]
virtual_screen_rect: (-1600 0) x (0 1200)