If I click some where in that listbox and minimize the installer and then maximize the installer the listbox is getting hidden, the problem is occurring due to set CreateWindowEx for a bitmap static control and set the bitmap there.
here is the code for create and set bmp image over the installer.
;System::Call `kernel32::GetModuleHandle(i 0) i.R3`
;System::Call `user32::CreateWindowEx(i 0, t "STATIC", t "", i ${SS_BITMAP}|${WS_CHILD}|${WS_VISIBLE}, i 0, i 0, i R1, i R2, i $HWNDPARENT, i ${IDC_BITMAP}, i R3, i 0) i.R1`
;System::Call `user32::SetWindowPos(i R1, i ${HWND_TOP}, i 0, i 0, i 0, i 0, i ${SWP_NOSIZE}|${SWP_NOMOVE})`
; Load & Set the bg bitmap.
System::Call `user32::LoadImage(i 0, t "$PLUGINSDIR\bg.bmp", i ${IMAGE_BITMAP}, i 0, i 0, i ${LR_CREATEDIBSECTION}|${LR_LOADFROMFILE}) i.s`
Pop $hBitmap
SendMessage $R1 ${STM_SETIMAGE} ${IMAGE_BITMAP} $hBitmap