I am using the “window” mapping type to apply some cartoony textures to my model in the EEVEE renderer and I noticed that depending upon the shape of the rendering window, the mapping will stretch and squash the texture I am using (a half-tone pattern). Having looked at the way the coordinates are generated, it would seem that the problem might be fundamental, but I wondered if anyone had found a way to work around the issue?
Turns out the issue is eliminated if the Camera Data > View Vector is used for texture coordinates rather than the Texture Coordinate > Window.