I am testing a »hacks« based workflow now with libsass in an external process and the compiling is done nearly instantaneous. With this workflow I can iterate. The »hacks« process seams to work, I don't know if Moodle will compile the same CSS when I remove the »hacks«. That I need to test.
Btw I work with the Mac program »CodeKit«, which is a web design build tool somehow similar to Grunt but with a GUI, which I prefer.
Someone from Moodle HQ mentioned that the external process could be optional. Something like - if an external process exists use it else use PHP. That would be great.
@Maina, how did you at Moodle HQ develop the boost theme when each cache clearing and theme rebuild takes a long time? Did you use workarounds or did you just sit and wait? Or may there be other options?
@Richard, I could imagine that Moodle writes the user added rawscss and variables form settings as a user preset SCSS file for example in moodledata. This file can be included into any external process for compiling.
Because of the speed advantage during theme development external SCSS processing would be a big win.
@Mary It's not only about the FontAwesome CSS, a major issue is the treepostprocessor.
And when these two issues may be solved the SCSS rendering in PHP is still much slower than with for example libsass. To get a convenient workflow it should be possible to use the proven standard SCSS renderers instead of the Moodle PHP ones.