Wrong result through Filter Offset

The shape of the glyph will be changed into another style of shape after I use Filter Offset.
test.glyphs (9.7 KB)

The shape above in the picture is square originally, but it becomes alien after Offset.
I don’t know the reason, can you help.

Which version of Glyphs?

Version 2.6.5(1329)

The problem is that you have TrueType curves. Those are not supported by the Offset Curve filter.

How can I solve it?
Or can I transform it into correct curve through script?

Menu > Path > Other > Convert to Cubic.

Got it.
Thanks :slight_smile: