Function glfwSetCursorEnterCallback 

pub unsafe extern "C" fn glfwSetCursorEnterCallback(
    window: *mut GLFWwindow,
    callback: Option<unsafe extern "C" fn(*mut GLFWwindow, i32)>,
) -> Option<unsafe extern "C" fn(*mut GLFWwindow, i32)>

@brief Sets the cursor enter/leave callback.

This function sets the cursor boundary crossing callback of the specified window, which is called when the cursor enters or leaves the content area of the window.

@param[in] window The window whose callback to set. @param[in] callback The new callback, or NULL to remove the currently set callback. @return The previously set callback, or NULL if no callback was set or the library had not been [initialized](@ref intro_init).

@callback_signature @code void function_name(GLFWwindow* window, int entered) @endcode For more information about the callback parameters, see the [function pointer type](@ref GLFWcursorenterfun).

@errors Possible errors include @ref GLFW_NOT_INITIALIZED.

@thread_safety This function must only be called from the main thread.

@sa @ref cursor_enter

@since Added in version 3.0.

@ingroup input