Bezier flattener flattens beziers too much

[jaseg]

Bezier flattener flattens beziers too much

[neinseg]

I can reproduce this. svg-flatten has a "curve tolerance" setting that is supposed to control this, but it seems that these curves don't even hit the flattener as changing that setting does not have an effect. I will look into this in detail tonight.

[neinseg]

I think I've fixed this issue. I've pushed the fix to the main branch. Please feel free to try it out.

For both svg-flatten and gerbolyze, the --curve-tolerance command-line argument now does what it says on the tin and sets the maximum tolerance for bezier flattening in mm. Gerbolyze will now happily generate micrometer-smooth curves in gerber files tens of megabytes in size ;)

The fix ended up being to completely rip out Cairo and replace its bezier flattener with part of Antigrain Graphics' one. A beneficial side effect of this is that it is a step towards Windows builds, since on Windows the Cairo dependency was an issue.

Unfortunately, while fixing this issue I have re-introduced a bug where clipper calculates the mask layer cutouts too small. This results in silkscreen being closer than intended to soldermask openings in some cases. As all board houses will remove any silk overlay on pads anyway this is a purely cosmetic issue, but I will hold off with a release of my fix until I have also fixed this problem.