The window whose callback to set.
The new callback, or null to remove the currently set callback.
The previously set callback, or null if no callback was set or the library had not been initialized.
@callback_signature
void function_name(GLFWwindow* window);
For more information about the callback parameters, see the function pointer type.
Errors: Possible errors include @ref GLFW_NOT_INITIALIZED.
This function must only be called from the main thread.
@sa @ref window_refresh
Added in version 2.5. @glfw3 Added window handle parameter and return value.
Ingroup: window
Sets the refresh callback for the specified window.
This function sets the refresh callback of the specified window, which is called when the content area of the window needs to be redrawn, for example if the window has been exposed after having been covered by another window.
On compositing window systems such as Aero, Compiz, Aqua or Wayland, where the window contents are saved off-screen, this callback may be called only very infrequently or never at all.