Using the absolute mouse position

The absolute mouse position is used primarily in window applications, where the mouse position constraints are desirable. The mouse position (0,0) corresponds to the upper-left corner of your application window. The maximum mouse position depends always on the size of the window. Take special care when the mouse cursor is outside the application window. The behavior of LuaSDL in this situation is highly dependent on the currently used operating system! In most cases, you won't get any events related to the mouse cursor motion.

The main advantage of this is that you can use the mouse cursor position reported directly by LuaSDL to precisely manipulate GUI elements inside of the application window. This approach is used also with tablet touch input devices, where you always get absolute positions.

How to do it…

The following mouse movement handler function shows a simple way to get the absolute mouse cursor position:

[SDL.SDL_MOUSEMOTION] = function(raw_event)
  local event = raw_event.motion

The absolute mouse position is stored in x and y attributes:

  mouseX = event.x
  mouseY = event.y
end,