Mouse and input coordinates

About

The reason for this small tutorial is to clear up many common mistakes about input coordinates, obtaining mouse position and screen resolution, etc.

Hardware display coordinates

Using hardware coordinates makes sense in the case of writing complex UIs meant to run on PC, such as editors, MMOs, tools, etc. Yet, it does not make as much sense outside of that scope.

Viewport display coordinates

Godot uses viewports to display content, and viewports can be scaled by several options (see Multiple resolutions tutorial). Use, then, the functions in nodes to obtain the mouse coordinates and viewport size, for example:

func _input(event):
   # Mouse in viewport coordinates
   if event is InputEventMouseButton:
       print("Mouse Click/Unclick at: ", event.position)
   elif event is InputEventMouseMotion:
       print("Mouse Motion at: ", event.position)

   # Print the size of the viewport
   print("Viewport Resolution is: ", get_viewport_rect().size)

func _ready():
    set_process_input(true)

Alternatively it’s possible to ask the viewport for the mouse position:

get_viewport().get_mouse_position()