[gtk+] Adwaita: provide simple guidelines for theming

[Jakub Steiner <jimmac src gnome org>]

commit 30149dabcf21693c2a29c5c3d669b4a006062e1e
Author: Jakub Steiner <jimmac gmail com>
Date:   Mon Sep 29 14:07:10 2014 +0200

    Adwaita: provide simple guidelines for theming
    
    - Some simple instructions for future SASS/ruby lovers

 gtk/resources/theme/Adwaita/README |   36 ++++++++++++++++++++++++++++++++++++
 1 files changed, 36 insertions(+), 0 deletions(-)
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diff --git a/gtk/resources/theme/Adwaita/README b/gtk/resources/theme/Adwaita/README
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+Summary
+-------
+
+* Do not edit the CSS directly, edit the source SCSS files and process them with SASS (run 
+  `/.parse-sass.sh` when you have the required sofwtare installed, as described below)
+* To be able to use the lates/adequate version of sass, install ruby, gem, sass & bundle. 
+  On Fedora F20, this is done with `sudo dnf install rubygems && gem install bundle && bundle install`
+  from the same directory this README resides in.
+
+How to tweak the theme
+----------------------
+
+Adwaita is a complex themes, so to keep it maintainable it's written and processed in SASS, the
+generated CSS is then transformed into a gresource file during gtk build and used at runtime in a 
+non-legible or editable form.
+
+It is very likely your change will happen in the _common.scss file. That's where most of the widget 
+selectors are defined. Here's a rundown of the "supporting" stylesheets, that are unlikely to be the 
+right place for a drive by stylesheet fix:
+
+_colors.scss        - global color definitions. We keep the number of defined colors to a necessary minimum, 
+                      most colors are derived form a handful of basics. It covers both the light variant and
+                      the dark variant.
+
+_colors-public.scss - SCSS colors exported through gtk to allow for 3rd party apps color mixing.
+
+_drawing.scss       - drawing helper mixings/functions to allow easier definition of widget drawing under
+                      specific context. This is why Adwaita isn't 15000 LOC.
+
+_common.scss        - actual definitions of style for each widget. This is where you are likely to add/remove
+                      your changes.
+                      
+You can read about SASS at http://sass-lang.com/documentation/. Once you make your changes to the
+_common.scss file, you can either run the ./parse-sass.sh script or keep SASS watching for changes as you
+edit. This is done by running `bundle exec sass --watch --sourcemap=none .` If sass is out of date, or is
+missing, you can install it with `bundle install`.