Add support for always-builtin features in the build system

Like image surface and user fonts.

1 files changed, 28 insertions, 15 deletions

diff --git a/build/configure.ac.enable b/build/configure.ac.enable
index 71e887b82..3c1dae63e 100644
--- a/build/configure.ac.enable
+++ b/build/configure.ac.enable
@@ -21,9 +21,10 @@ dnl		"font" for font backends
 dnl		"functions" for set of functions
 dnl		"" for private configurations
 dnl	DEFAULT is the default state of the feature:
-dnl		"no" for experimental backends, eg. your favorite new backend
-dnl		"yes" for mandatory backends, eg. png
-dnl		"auto" for other supported backends, eg. xlib
+dnl		"no" for experimental features, eg. your favorite new backend
+dnl		"yes" for recommended features, eg. png functions
+dnl		"auto" for other supported features, eg. xlib surface backend
+dnl		"always" for mandatory features (can't be disabled), eg. image surface backend
 dnl	COMMANDS are run to check whether the feature can be enabled.  Their
 dnl		result may be cached, so user should not count on them being run.
 dnl		They should set use_$(ID) to something other than yes if the
@@ -56,13 +57,19 @@ AC_DEFUN([_CAIRO_ENABLE],
 		[no],,
 		[yes],,
 		[auto],,
+		[always],,
 		[m4_fatal([Invalid default value `]cr_feature_default[' for feature `]cr_feature['])]
 	)
 
-	AC_ARG_ENABLE(cr_feature_arg,
-		      AS_HELP_STRING([--enable-]cr_feature_arg[=@<:@no/auto/yes@:>@],
-				     [Enable cairo's ]cr_feature_name[ feature @<:@default=]cr_feature_default[@:>@]),
-		      enable_$1=$enableval, enable_$1=cr_feature_default)
+	m4_if(cr_feature_default, [always],
+	[
+		enable_$1=yes
+	],[
+		AC_ARG_ENABLE(cr_feature_arg,
+			      AS_HELP_STRING([--enable-]cr_feature_arg[=@<:@no/auto/yes@:>@],
+					     [Enable cairo's ]cr_feature_name[ feature @<:@default=]cr_feature_default[@:>@]),
+			      enable_$1=$enableval, enable_$1=cr_feature_default)
+	])
 	case $enable_$1 in
 	no)
 		use_$1="no (disabled, use --enable-cr_feature_arg to enable)"
@@ -120,7 +127,12 @@ AC_DEFUN([_CAIRO_ENABLE],
 
 		AS_IF([test "x$enable_$1" = "xyes" -a "x$use_$1" != xyes],
 		[
-			AC_MSG_ERROR([requested ]cr_feature_name[ feature could not be enabled])
+			AC_MSG_ERROR(
+				m4_case(cr_feature_default,
+					[always],	[mandatory],
+					[yes],		[recommended],
+					,		[requested]
+				) cr_feature_name[ feature could not be enabled])
 		])
 	;;
 	*)
@@ -236,9 +248,10 @@ dnl
 dnl	cr_feature expands to the feature id, eg "ft"
 dnl	cr_feature_name	expands to the human-readable name of the feature, eg. "FreeType font"
 dnl	cr_feature_default expands to the default state of the feature:
-dnl		"no" for experimental backends, eg. your favorite new backend
-dnl		"yes" for mandatory backends, eg. png
-dnl		"auto" for other supported backends, eg. xlib
+dnl		"no" for experimental features, eg. your favorite new backend
+dnl		"yes" for recommended features, eg. png functions
+dnl		"auto" for other supported features, eg. xlib surface backend
+dnl		"always" for mandatory features (can't be disabled), eg. image surface backend
 dnl	cr_what expands to the type of feature:
 dnl		"surface" for surface backends
 dnl		"font" for font backends
@@ -487,8 +500,8 @@ CAIRO_FEATURE_VARS_REGISTER([REQUIRES BASE])
 CAIRO_FEATURE_VARS_REGISTER([CFLAGS NONPKGCONFIG_CFLAGS])
 CAIRO_FEATURE_VARS_REGISTER([LIBS NONPKGCONFIG_LIBS], [$LIBS])
 
-dnl Generate .pc files for enabled public features
-CAIRO_FEATURE_HOOK_REGISTER(yes,*,!,
+dnl Generate .pc files for enabled non-builtin public features
+CAIRO_FEATURE_HOOK_REGISTER(yes,!always,!,
 [
 	AC_CONFIG_FILES(src/cr_feature_pc:src/cairo-features.pc.in,
 	[
@@ -510,8 +523,8 @@ CAIRO_FEATURE_HOOK_REGISTER(yes,*,!,
 	])
 ])
 
-dnl Generate -uninstalled.pc files for enabled public features
-CAIRO_FEATURE_HOOK_REGISTER(yes,*,!,
+dnl Generate -uninstalled.pc files for enabled non-builtin public features
+CAIRO_FEATURE_HOOK_REGISTER(yes,!always,!,
 [
 	AC_CONFIG_FILES(cr_feature_uninstalled_pc:src/cairo-features-uninstalled.pc.in,
 	[