[clutter] build: Automatically detect Wayland support

[Emmanuele Bassi <ebassi src gnome org>]

commit d09c204a266385626c40d851b6fbadf7a134aaa0
Author: Emmanuele Bassi <ebassi gnome org>
Date:   Tue Jun 30 14:47:08 2015 +0100

    build: Automatically detect Wayland support
    
    Like we do for X11, GDK, MacOS, and Windows, the Wayland backend can be
    autodetected. We should only fail if the Wayland support was explicitly
    asked at configure time, but the dependencies were not satisfied.

 configure.ac |   29 ++++++++++++++++++++---------
 1 files changed, 20 insertions(+), 9 deletions(-)
---
diff --git a/configure.ac b/configure.ac
index 3be2430..1f6201c 100644
--- a/configure.ac
+++ b/configure.ac
@@ -268,7 +268,7 @@ AC_ARG_ENABLE([gdk-backend],
 AC_ARG_ENABLE([wayland-backend],
               [AS_HELP_STRING([--enable-wayland-backend=@<:@yes/no@:>@], [Enable the Wayland client backend 
(default=no)])],
               [enable_wayland=$enableval],
-              [enable_wayland=no])
+              [enable_wayland=check])
 AC_ARG_ENABLE([egl-backend],
               [AS_HELP_STRING([--enable-egl-backend=@<:@yes/no@:>@], [Enable the EGL framebuffer backend 
(default=no)])],
               [enable_egl=$enableval],
@@ -335,7 +335,7 @@ AS_IF([test "x$enable_gdk" = "xyes"],
        BACKEND_PC_FILES="$BACKEND_PC_FILES gdk-3.0"
       ])
 
-AS_IF([test "x$enable_wayland" = "xyes"],
+AS_IF([test "x$enable_wayland" != xno],
       [
         CLUTTER_BACKENDS="$CLUTTER_BACKENDS wayland"
         CLUTTER_INPUT_BACKENDS="$CLUTTER_INPUT_BACKENDS wayland"
@@ -365,14 +365,25 @@ AS_IF([test "x$enable_wayland" = "xyes"],
                          have_cogl_wayland=no
                        ])
         CFLAGS="${saved_CFLAGS}"
-        AS_IF([test "x$have_cogl_wayland" = xno], [AC_MSG_ERROR("*** Cogl is missing Wayland support.")])
+        AS_IF([test "x$have_cogl_wayland" = xyes],
+              [
+                PKG_CHECK_EXISTS([wayland-client wayland-cursor xkbcommon gdk-pixbuf-2.0],
+                                 [
+                                   BACKEND_PC_FILES="$BACKEND_PC_FILES wayland-cursor wayland-client 
xkbcommon"
+                                   BACKEND_PC_FILES_PRIVATE="$BACKEND_PC_FILES_PRIVATE gdk-pixbuf-2.0"
+                                 ],
+                                 [
+                                   AS_IF([test "x$enable_wayland" = xyes],
+                                         [AC_MSG_ERROR(["*** Missing dependencies for Wayland support 
***"])],
+                                         [enable_wayland=no])
+                                 ])
+              ],
+              [
+                AS_IF([test "x$enable_wayland" = xyes],
+                      [AC_MSG_ERROR("*** Cogl is missing Wayland support ***")],
+                      [enable_wayland=no])
+              ])
 
-        PKG_CHECK_EXISTS([wayland-client wayland-cursor xkbcommon gdk-pixbuf-2.0],
-                         [
-                            BACKEND_PC_FILES="$BACKEND_PC_FILES wayland-cursor wayland-client xkbcommon"
-                            BACKEND_PC_FILES_PRIVATE="$BACKEND_PC_FILES_PRIVATE gdk-pixbuf-2.0"
-                         ],
-                         [])
       ])
 
 dnl Note this is orthogonal to the client side support and you can