In order to get a 100px corner, I need to enter a radius of 98 into the Round Corners. Likewise a 200px corner requires I enter a radius 196.
However if I copy the setting using the cog menu and add the Round Corners as a Custom Parameter Filter I get a different result. If I export an OTF the values are different. A CP value of 98 creates a 98px corner. Is this a bug?
I’ve been using both the normal filter and the CP recently and I’m having to adjust the values to get what I want. For example applying a radius of 40 results in a corner of 41u. There’s something iffy going on with the accuracy of Glyphs, it isn’t as accurate as it should be. See my other post here Rounding errors when scaling when none should occur
Sorry, I meant to say visual correction is disabled. In this case applying a value of 100 results in a corner radius of 102 u/em.
I’ll have to go back and have another go with the original font file to see if I can find the differences between the CP and applying the filter. It had a quick go at making a simple two glyph test file but I couldn’t recreate the differences this time.
I also tested this using only a single CP, in case doubling it up was causing the difference. It didn’t make a difference. It appears that the CP is applying the filter accurately but doing it from the menu command produces the wrong result.