add separate css file for gtk-3.20

configure.ac

@@ -30,6 +30,12 @@ PKG_CHECK_MODULES([WEB_EXTENSION], [
     webkit2gtk-web-extension-4.0 >= 2.10.8
 ])
 
+PKG_CHECK_MODULES([GREETER], [gtk+-3.0 >= 3.20],
+   [AC_DEFINE([HAVE_GTK320], [1], [Use Gtk320])],
+       [AC_DEFINE([HAVE_GTK320], [0], [Use Gtk320])]
+)
+AM_CONDITIONAL([HAVE_GTK320], [test "$HAVE_GTK320" -eq 1])
+
 AC_SUBST([WEB_EXTENSION_CFLAGS])
 AC_SUBST([WEB_EXTENSION_LIBS])
 

src/Makefile.am

@@ -1,7 +1,13 @@
 webextension_LTLIBRARIES = liblightdm-webkit2-greeter-ext.la
 webextensiondir = $(libdir)/lightdm-webkit2-greeter
 
-lightdm-webkit2-greeter-css-application.h: $(srcdir)/lightdm-webkit2-greeter-application.css Makefile
+if HAVE_GTK320
+ldmcssfile = lightdm-webkit2-greeter-application-3.20.css
+else
+ldmcssfile = lightdm-webkit2-greeter-application.css
+endif
+
+lightdm-webkit2-greeter-css-application.h: $(srcdir)/$(ldmcssfile) Makefile
 	$(AM_V_GEN) exo-csource --static --name=lightdm_webkit2_greeter_css_application $< >$@
 
 liblightdm_webkit2_greeter_ext_la_SOURCES = lightdm-webkit2-greeter-ext.c

src/lightdm-webkit2-greeter-application-3.20.css

@@ -0,0 +1,3 @@
+window {
+	background: #000000;
+}

src/lightdm-webkit2-greeter-application.css

@@ -1,3 +1,3 @@
 GtkWindow {
-    background: #000000;
-}
+	background: #000000;
+}