[PATCH v3] configure.ac: Allow forcible disabling of Cairo support

[Daniel Stone <daniel@fooishbar.org>]

We don't want to build libdrm tests with Cairo support under Poky, since
they're never used and also cause a build loop from libdrm -> cairo ->
mesa-dri -> libdrm.

To avoid variance in build results, introduce a --disable-cairo-tests
switch.

Signed-off-by: Daniel Stone <daniel@fooishbar.org>
---
 configure.ac               |   18 +++++++++++++++---
 tests/modetest/Makefile.am |   11 +++++++----
 2 files changed, 22 insertions(+), 7 deletions(-)

v3: Don't link against Cairo if it's been found but disabled.  Last one, I
    promise.

diff --git a/configure.ac b/configure.ac
index 290362c..8c28107 100644
--- a/configure.ac
+++ b/configure.ac
@@ -222,11 +222,23 @@ if test "x$EXYNOS" = xyes; then
 	AC_DEFINE(HAVE_EXYNOS, 1, [Have EXYNOS support])
 fi
 
+AC_ARG_ENABLE([cairo-tests],
+              [AS_HELP_STRING([--enable-cairo-tests],
+                              [Enable support for Cairo rendering in tests (default: auto)])],
+              [CAIRO=$enableval], [CAIRO=auto])
 PKG_CHECK_MODULES(CAIRO, cairo, [HAVE_CAIRO=yes], [HAVE_CAIRO=no])
-if test "x$HAVE_CAIRO" = xyes; then
-	AC_DEFINE(HAVE_CAIRO, 1, [Have cairo support])
+AC_MSG_CHECKING([whether to enable Cairo tests])
+if test "x$CAIRO" = xauto; then
+	CAIRO="$HAVE_CAIRO"
 fi
-AM_CONDITIONAL(HAVE_CAIRO, [test "x$HAVE_CAIRO" = xyes])
+if test "x$CAIRO" = xyes; then
+	if ! test "x$HAVE_CAIRO" = xyes; then
+		AC_MSG_ERROR([Cairo support required but not present])
+	fi
+	AC_DEFINE(HAVE_CAIRO, 1, [Have Cairo support])
+fi
+AC_MSG_RESULT([$CAIRO])
+AM_CONDITIONAL(HAVE_CAIRO, [test "x$CAIRO" = xyes])
 
 # For enumerating devices in test case
 PKG_CHECK_MODULES(LIBUDEV, libudev, [HAVE_LIBUDEV=yes], [HAVE_LIBUDEV=no])
diff --git a/tests/modetest/Makefile.am b/tests/modetest/Makefile.am
index b5ec771..065ae13 100644
--- a/tests/modetest/Makefile.am
+++ b/tests/modetest/Makefile.am
@@ -1,8 +1,7 @@
 AM_CFLAGS = \
 	-I$(top_srcdir)/include/drm \
 	-I$(top_srcdir)/libkms/ \
-	-I$(top_srcdir) \
-	$(CAIRO_CFLAGS)
+	-I$(top_srcdir)
 
 noinst_PROGRAMS = \
 	modetest
@@ -12,5 +11,9 @@ modetest_SOURCES = \
 
 modetest_LDADD = \
 	$(top_builddir)/libdrm.la \
-	$(top_builddir)/libkms/libkms.la \
-	$(CAIRO_LIBS)
+	$(top_builddir)/libkms/libkms.la
+
+if HAVE_CAIRO
+AM_CFLAGS += $(CAIRO_CFLAGS)
+modetest_LDADD += $(CAIRO_LIBS)
+endif
-- 
1.7.10.4