Coordsys gizmo

In maya and 3dsmax a coordsys is displayed in the lower left corner. I want to render that in my app (only the 3 lines with different colors, not the text). But how to do that??? The specs are:

  1. 3 lines, each with different color.
  2. Coordsys should be placed in the same position (2d wise) in the corner
  3. Coordsys should not change size when changing aspect ratio or viewport size.

1 is easy, but 2 and 3… hmmm, any help appreciated…

I was going to explain some stuff: but this may help instead;

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