theme: Pre-generate stylesheets as well

Since commit 9ef9a5ff8a, man pages are generated at dist time to reduce
build dependencies when building from a released tarball.

Do the same for the stylesheets to also remove the sassc dependency.

Part-of: <https://gitlab.gnome.org/GNOME/gnome-shell/-/merge_requests/1555>

data/meson.build

@@ -41,6 +41,7 @@ foreach service_file : service_files
   )
 endforeach
 
+theme_deps = []
 
 subdir('dbus-interfaces')
 subdir('icons')

data/theme/meson.build

@@ -42,20 +42,21 @@ theme_sources = files([
   'gnome-shell-sass/widgets/_workspace-thumbnails.scss'
 ])
 
-styles = [
-  'gnome-shell-high-contrast',
-  'gnome-shell'
+stylesheets = [
+  'gnome-shell-high-contrast.css',
+  'gnome-shell.css'
 ]
 
-theme_deps = []
-
-foreach style: styles
-  theme_deps += custom_target('style-' + style,
-                              input: '@0@.scss'.format(style),
-                              output: '@0@.css'.format(style),
+foreach stylesheet: stylesheets
+  if not fs.exists(stylesheet)
+    sassc = find_program('sassc')
+    theme_deps += custom_target(stylesheet,
+                                input: fs.replace_suffix(stylesheet, '.scss'),
+                                output: stylesheet,
                                 command: [
                                   sassc, '-a', '@INPUT@', '@OUTPUT@'
                                 ],
                                 depend_files: theme_sources)
+  endif
 endforeach
 

meson.build

@@ -137,7 +137,6 @@ endif
 
 mutter_typelibdir = mutter_dep.get_pkgconfig_variable('typelibdir')
 python = find_program('python3')
-sassc = find_program('sassc')
 gjs = find_program('gjs')
 
 cc = meson.get_compiler('c')
@@ -293,6 +292,7 @@ endif
 
 meson.add_install_script('meson/postinstall.py')
 meson.add_dist_script('meson/generate-manpages.py')
+meson.add_dist_script('meson/generate-stylesheets.py')
 
 summary_options = {
   'networkmanager': get_option('networkmanager'),

meson/generate-stylesheets.py

@@ -0,0 +1,19 @@
+#!/usr/bin/env python3
+
+import os
+from pathlib import PurePath
+import subprocess
+
+stylesheets = [
+    'data/theme/gnome-shell-high-contrast.css',
+    'data/theme/gnome-shell.css'
+]
+
+sourceroot = os.environ.get('MESON_SOURCE_ROOT')
+distroot = os.environ.get('MESON_DIST_ROOT')
+
+for stylesheet in stylesheets:
+    stylesheet_path = PurePath(stylesheet)
+    src = PurePath(sourceroot, stylesheet_path.with_suffix('.scss'))
+    dst = PurePath(distroot, stylesheet_path)
+    subprocess.call(['sassc', '-a', src, dst])