WM_KEYUP top-level constant
int
const WM_KEYUP
Posted to the window with the keyboard focus when a nonsystem key is released.
A nonsystem key is a key that is pressed when the ALT key is not pressed, or a keyboard key that is pressed when a window has the keyboard focus.
To learn more, see learn.microsoft.com/windows/win32/inputdev/wm-keyup.
Implementation
const WM_KEYUP = 257;