build: Require sassc for classic style

Meson has a strict separation of source- and build directory, and
expects anything generated in the latter. That means that in order
to maintain our current setup - shipping the generated CSS in the
repo while also optionally updating it automatically when sassc is
found - we have to fight the build system to some extent, which makes
it less reliable than we would like.

Since we switched to sassc which is a more acceptable build-time
dependency than the original ruby-based tool, just drop the CSS
from the repo and unconditionally generate it from SASS if classic
mode is enabled.

https://gitlab.gnome.org/GNOME/gnome-shell-extensions/merge_requests/28

data/HACKING

@@ -1,6 +1,2 @@
-To generate the css files, from the project directory:
-
-sassc -a gnome-classic.scss gnome-classic.css
-
 To update the gnome-shell-sass submodule to latest upstream commit:
 git submodule update --rebase

data/meson.build

@@ -43,22 +43,18 @@ theme_data = [
   'classic-toggle-off-us.svg',
   'classic-toggle-on-intl.svg',
   'classic-toggle-on-us.svg',
-  'gnome-classic.css',
   'gnome-classic-high-contrast.css'
 ]
 
-update_theme = files('update-theme.sh')
-
-if sassc.found()
-  style = 'gnome-classic'
-  custom_target(style + '.css',
-    input: style + '.scss',
-    output: style + '.css',
-    depend_files: theme_sources + files(style + '.css'),
-    command: [update_theme, '@INPUT@', '@OUTPUT@'],
-    build_by_default: true
-  )
-endif
+style = 'gnome-classic'
+custom_target(style + '.css',
+  input: style + '.scss',
+  output: style + '.css',
+  depend_files: theme_sources,
+  command: [sassc, '-a', '@INPUT@', '@OUTPUT@'],
+  install: true,
+  install_dir: themedir
+)
 
 install_data(theme_data, install_dir: themedir)
 

data/update-theme.sh

@@ -1,9 +0,0 @@
-#!/bin/sh
-
-INPUT=$1
-OUTPUT=$2
-
-if [ `which sassc` ]
-then
-  sassc -a $INPUT | tee ${INPUT%%.scss}.css > $OUTPUT
-fi

meson.build

@@ -23,7 +23,6 @@ xsessiondir = join_paths(datadir, 'xsession')
 extensionlib = files('lib/convenience.js')
 
 js52 = find_program('js52', required: false)
-sassc = find_program('sassc', required: false)
 
 ver_arr = meson.project_version().split('.')
 if ver_arr[1].to_int().is_even()
@@ -92,6 +91,7 @@ foreach e : enabled_extensions
 endforeach
 
 if classic_mode_enabled
+  sassc = find_program('sassc', required: true)
   subdir('data')
 endif