Optionally depend on sassc to generate the theme CSS

Instead of using Ruby/Sass to generate the CSS from SCSS files, we can
use the faster and more lightweight libsass/sassc binary.

We can keep the CSS files in Git to make it easier to dist GTK+, but we
can add rules to ensure they get rebuilt if the source SCSS changes.

https://bugzilla.gnome.org/show_bug.cgi?id=780041

2 files changed, 49 insertions, 16 deletions

diff --git a/configure.ac b/configure.ac
index 45313193c6..9be280972a 100644
--- a/configure.ac
+++ b/configure.ac
@@ -1869,6 +1869,14 @@ esac
 AC_SUBST(GDK_HIDDEN_VISIBILITY_CFLAGS)
 
 ##################################################
+# Theming
+##################################################
+
+AC_PATH_PROG([SASSC], [sassc])
+AC_ARG_VAR(SASSC)
+AM_CONDITIONAL([REBUILD_SCSS], [test "xSASSC" != x])
+
+##################################################
 # Output commands
 ##################################################
 
diff --git a/gtk/Makefile.am b/gtk/Makefile.am
index e0124e5eed..9adab54393 100644
--- a/gtk/Makefile.am
+++ b/gtk/Makefile.am
@@ -1283,36 +1283,61 @@ gesture_sources = 				\
 	gesture/gesture-two-finger-swipe-left-symbolic.svg	\
 	gesture/gesture-two-finger-swipe-right-symbolic.svg
 
-theme_sources = 				\
-	theme/win32/gtk.css	 		\
-	theme/win32/gtk-win32-base.css 		\
-	theme/Adwaita/assets.txt 		\
-	theme/Adwaita/assets.svg 		\
+adwaita_theme_scss = \
 	theme/Adwaita/_colors-public.scss 	\
 	theme/Adwaita/_colors.scss 		\
 	theme/Adwaita/_common.scss 		\
 	theme/Adwaita/_drawing.scss 		\
 	theme/Adwaita/gtk-contained-dark.scss 	\
 	theme/Adwaita/gtk-contained.scss 	\
-	theme/Adwaita/parse-sass.sh 		\
-	theme/Adwaita/render-assets.sh 		\
-	theme/Adwaita/Gemfile 			\
-	theme/Adwaita/README 			\
-	theme/Adwaita/gtk-contained.css 	\
-	theme/Adwaita/gtk-contained-dark.css 	\
-	theme/Adwaita/gtk.css 			\
-	theme/Adwaita/gtk-dark.css 		\
+	$()
+
+highcontrast_theme_scss = \
 	theme/HighContrast/_colors.scss 	\
 	theme/HighContrast/_common.scss 	\
 	theme/HighContrast/_drawing.scss 	\
 	theme/HighContrast/gtk-contained-inverse.scss \
 	theme/HighContrast/gtk-contained.scss 	\
-	theme/HighContrast/Gemfile 		\
+	$()
+
+if REBUILD_SCSS
+# If we have sassc then we can rebuild the theme CSS as soon as the SCSS
+# files have been changed
+
+scss_verbose = $(scss_verbose_@AM_V@)
+scss_verbose_ = $(scss_verbose_@AM_DEFAULT_V@)
+scss_verbose_0 = @echo "  SCSS     $@";
+
+theme/Adwaita/gtk-contained.css: $(top_srcdir)/gtk/theme/Adwaita/gtk-contained.scss
+	$(scss_verbose) $(MKDIR_P) $(dir $@) && $(SASSC) -a $< $@ || rm -f $@
+
+theme/Adwaita/gtk-contained-dark.css: $(top_srcdir)/gtk/theme/Adwaita/gtk-contained-dark.scss
+	$(scss_verbose) $(MKDIR_P) $(dir $@) && $(SASSC) -a $< $@ || rm -f $@
+
+theme/HighContrast/gtk-contained.css: $(top_srcdir)/gtk/theme/HighContrast/gtk-contained.scss
+	$(scss_verbose) $(MKDIR_P) $(dir $@) && $(SASSC) -a $< $@ || rm -f $@
+
+theme/HighContrast/gtk-contained-inverse.css: $(top_srcdir)/gtk/theme/HighContrast/gtk-contained-inverse.scss
+	$(scss_verbose) $(MKDIR_P) $(dir $@) && $(SASSC) -a $< $@ || rm -f $@
+
+endif # REBUILD_SCSS
+
+theme_sources = 				\
+	theme/win32/gtk.css	 		\
+	theme/win32/gtk-win32-base.css 		\
+	$(adwaita_theme_scss)			\
+	theme/Adwaita/assets.txt 		\
+	theme/Adwaita/assets.svg 		\
+	theme/Adwaita/README 			\
+	theme/Adwaita/gtk-contained.css 	\
+	theme/Adwaita/gtk-contained-dark.css 	\
+	theme/Adwaita/gtk.css 			\
+	theme/Adwaita/gtk-dark.css 		\
+	$(highcontrast_theme_scss)		\
 	theme/HighContrast/gtk-contained.css 	\
 	theme/HighContrast/gtk-contained-inverse.css \
 	theme/HighContrast/gtk.css 		\
-	theme/HighContrast/gtk-inverse.css 	\
-	theme/HighContrast/parse-sass.sh
+	theme/HighContrast/gtk-inverse.css
 
 resource_files = $(shell $(GLIB_COMPILE_RESOURCES) --sourcedir=$(srcdir) --generate-dependencies $(builddir)/gtk.gresource.xml)