Hi Guillaume, I would be in favor to add SASS and not replace Less with SASS if possible. Since the next one PostCSS is based on standard CSS, we would have multiple possibilities PostCSS, LESS+PostCSS or SASS+PostCSS. Basically it means supporting one extended CSS language processor followed by one or more standard CSS processors. Do you think that you could make your code generic enough to support both SASS and LESS, and be prepare to append PostCSS to the overall process ? Having this flexibility will allow backward compatibility and be open to the future. I am not sure waiting is the way to go, we basically need more flexibility. If you wait for something stable you risk to wait for ever.

Thanks, On Thu, Sep 17, 2015 at 8:01 PM, vincent(a)massol.net wrote: > Hi Guillaume, > > On 17 Sep 2015 at 18:59:22, Guillaume Louis-Marie Delhumeau ( > gdelhumeau@xwiki.com(mailto:gdelhumeau@xwiki.com)) wrote: > > > Hello everyone. > > > > The front-end world is evolving really fast, and it's very hard to pick > the > > good JavaScript framework, the good CSS preprocessor, or the good CSS > > toolkit. It's so unpredictable that it has inspired a comic strip: > > > http://www.commitstrip.com/en/2015/09/16/how-to-choose-the-right-javascript… > > :) > > > > Last year, we have chosen to use Bootstrap for our new Flamingo Skin. > > Quickly, I have discovered that we had to integrate a CSS preprocessor to > > be able to customize it [1]. The natural choice was Less, since Bootstrap > > and of lot themes of the web were using it. > > > > Now, the situation have changed. Bootstrap 4.0 will be released soon [2]. > > It have been entirely rewritten and some retro-incompatibilities have > been > > made. But the most breaking change is that they don't use Less anymore, > but > > Sass. > > > > By the past, they use a less-to-sass converter so they were able to > propose > > both versions of the framework. But now, I doubt the opposite converter > > could be possible since Sass have more features than Less. > > > > Worse, it seems that Sass is becoming more popular than Less [3]. > > > > Note: the current Bootstrap version, 3.x, will be maintained during one > > year, so we have this time to adapt. > > > > If we want to upgrade to Bootstrap 4, we will need to integrate the Sass > > preprocessor. Fortunately, we can re-use a lot of the work that I've done > > for Less (the cache mechanism, etc...) that I can modify to be more > > generic. I don't have estimated the time it would take yet. > > > > If we want to upgrade Flamingo to Bootstrap 4, it will create some css > > breakage (and the ability to use LESS in SSX will be loose). And we will > > have to convert our Less code to Sass. > > > > We could also decide to keep Bootstrap 3.x in Flamingo and use Bootstrap > 4 > > for our next skin. > > Why couldn’t we use LESS in SSX since in the end it generates CSS? > > Note that even SASS may not last very long (see this fun tweet: > https://twitter.com/mdo/status/591364406816079873?lang=en). > > For example there’s postCSS now (and lots of others): > * https://twitter.com/jeremychone/status/636570198510735360 > * https://github.com/postcss/postcss > * "PostCSS can do the same work as preprocessors like Sass, Less, and > Stylus. But PostCSS is modular, 3-30 times faster, and much more powerful." > * Some slides: http://ai.github.io/about-postcss/en/ > > Our only real solution would be to be able to have XWiki work with several > but I don’t know how hard it is to convert the bootstrap CSS files. > > See for example https://github.com/OEvgeny/bootstrap-postcss > > Since BS3 is pretty often used, I’m pretty sure people will develop > converters from LESS to SASS or others. > > So I think it’s important that we wait a bit :) We should research the > topic though. > > Thanks > -Vincent > > > Thanks, > > > > [1]: > > > http://design.xwiki.org/xwiki/bin/view/Proposal/ColorThemeforFlamingo#HImpl… > > [2]: Bootstrap 4 announcement: > > http://blog.getbootstrap.com/2015/08/19/bootstrap-4-alpha/ > > [3]: The State of Front-End Tooling – 2015: > > http://ashleynolan.co.uk/blog/frontend-tooling-survey-2015-results > > > > -- > > Guillaume Delhumeau (gdelhumeau(a)xwiki.com)

I don't know the amount of work needed, but it would be interesting to be able to support multiple preprocessors. Flamingo could remain on BS3+Less, but we could create a new skin on BS4. Regarding Sass, this is personal, but I'd prefer to jump directly to PostCSS, than to go through a Sass skin version. Thanks, Caty On Fri, Sep 18, 2015 at 1:15 PM, vincent(a)massol.net <vincent(a)massol.net> wrote: