xlib: Fix compilation when gradient functions are not available

It is not correct to rely on the version defined in render.h. The
Xrender.h header is independent and might not define some functions
available in RENDER 0.10.

Their availability must be detected at configure time and the stubs
must be defined only if the functions are not available.

Fixes https://bugs.freedesktop.org/show_bug.cgi?id=31906

2 files changed, 23 insertions, 9 deletions

diff --git a/configure.ac b/configure.ac
index f2c75cfb8..bb3d1d64b 100644
--- a/configure.ac
+++ b/configure.ac
@@ -83,6 +83,15 @@ CAIRO_ENABLE_SURFACE_BACKEND(xlib_xrender, Xlib Xrender, auto, [
 				       [use_xlib_xrender="no (requires $xlib_xrender_REQUIRES http://freedesktop.org/Software/xlibs)"])
 		       CPPFLAGS=$old_CPPFLAGS
 		      ])
+
+    old_CFLAGS=$CFLAGS
+    old_LIBS=$LIBS
+    CFLAGS="$CFLAGS $xlib_CFLAGS $xlib_NONPKGCONFIG_CFLAGS $xlib_xrender_CFLAGS $xlib_xrender_NONPKGCONFIG_CFLAGS"
+    LIBS="$LIBS $xlib_LIBS $xlib_NONPKGCONFIG_LIBS $xlib_xrender_LIBS $xlib_xrender_NONPKGCONFIG_LIBS"
+    AC_CHECK_FUNCS([XRenderCreateLinearGradient XRenderCreateRadialGradient XRenderCreateConicalGradient])
+    CFLAGS=$old_CFLAGS
+    LIBS=$old_LIBS
+
   fi
 ])
 
diff --git a/src/cairo-xlib-xrender-private.h b/src/cairo-xlib-xrender-private.h
index 52f415915..bf3199c4c 100644
--- a/src/cairo-xlib-xrender-private.h
+++ b/src/cairo-xlib-xrender-private.h
@@ -96,26 +96,31 @@ __attribute__((__unused__)) static void   _void_consume_free   (Display *p, XID
 #define PictOpBlendMaximum			    0x3e
 #endif
 
-/* There doesn't appear to be a simple #define that we can conditionalize
- * on.  Instead, use the version; gradients were introdiced in 0.10. */
-#if RENDER_MAJOR == 0 && RENDER_MINOR < 10
+#if !HAVE_XRENDERCREATELINEARGRADIENT
 #define XRenderCreateLinearGradient			_int_consume
+
+typedef struct _XLinearGradient {
+    XPointFixed p1;
+    XPointFixed p2;
+} XLinearGradient;
+#endif
+
+#if !HAVE_XRENDERCREATERADIALGRADIENT
 #define XRenderCreateRadialGradient			_int_consume
-#define XRenderCreateConicalGradient			_int_consume
+
 typedef struct _XCircle {
     XFixed x;
     XFixed y;
     XFixed radius;
 } XCircle;
-typedef struct _XLinearGradient {
-    XPointFixed p1;
-    XPointFixed p2;
-} XLinearGradient;
-
 typedef struct _XRadialGradient {
     XCircle inner;
     XCircle outer;
 } XRadialGradient;
+#endif
+
+#if !HAVE_XRENDERCREATECONICALGRADIENT
+#define XRenderCreateConicalGradient			_int_consume
 
 typedef struct _XConicalGradient {
     XPointFixed center;