I agree that for FreeType it makes more sense to port the algorithms to C than to complicate the build system by bringing in Rust. (I think Rust has a lot of potential for this kind of work, but I see that as a quite separate project).
I have come up with an extremely good algorithm for cubic to linear conversion, it's at https://levien.com/tmp/flatten.html. The lyon people have ported this to Rust, see https://github.com/nical/lyon/pull/552. It's based on ideas from my blog post https://raphlinus.github.io/graphics/curves/2019/12/23/flatten-quadbez.html but goes beyond it. I believe that this algorithm is very near optimal in both speed and quality. If selected as a mentor, I will write it up as a paper (ideally for submission to jctg), and there would be an opportunity for the student to coauthor that. Experience on resvg is a good qualification for this work :) Raph On Wed, Mar 25, 2020 at 7:42 AM Werner LEMBERG <w...@gnu.org> wrote: > > Hello Moazin, > > > > I am applying to GSoC this year as well and I am particularly > > interested in the project "Port the font-rs/fontdue rendering engine > > to FreeType". > > Great! > > > Firstly, I saw that the project obviously requires knowing Rust. > > While I am not a Rust programmer, I do know many of the basics due > > to my experience with `resvg' last year. I'm able to easily read > > and understand Rust code. I'm also going to be improving my > > knowledge of Rust as I further prepare the proposal. I guess this > > should be sufficient? > > Yes, I think. > > > [...] The actual raster part is mostly in `src/raster.rs' which is > > quite small. Also, creating a C wrapper for Rust code is an easy > > process (compared to other programming languages). Given the small > > size of the rendering engine it seems that implementing it from > > scratch in C inside FreeType isn't too hard either. Though I don't > > know if there is any advantage to doing that? The dependency issue > > maybe? > > Please always have embedded systems in mind. On such platforms it's > rather unlikely to find a Rust compiler, thus a conversion to C sounds > sensible. > > > Another thing I saw was that this engine can't handle Cubic Bezier > > curves, only Quadratic. FreeType does support font formats which > > use Cubic Bezier curves. So maybe I can add this functionality to it > > as part of this project. (unless there is something in the > > algorithm that can't be applied on Cubic curves or other font > > formats in general) > > I think this would be a very useful addition. Raph? > > > I think that porting can be done by: > > > > 1. Creating a C wrapper for font-rs (for the rendering part at > > least). > > Well, *only* the rendering part, since the rest is done by FreeType > already. > > > 2. Creating a new rendering module in FreeType that can provide the > > necessary "glue" code. > > Yes. As mentioned above, a conversion to C would be useful, too. > > I don't have any special tips or requirements for a proposal. :-) > > > Werner >