[dconf] Allow building against GTK+ 3

[Matthias Clasen <matthiasc src gnome org>]

commit ed8d0d54e336f7bbd87cea3bf86ec1b4be795c20
Author: Matthias Clasen <mclasen redhat com>
Date:   Sun Oct 3 17:51:03 2010 -0400

    Allow building against GTK+ 3
    
    This commit adds the customary --with-gtk configure option.
    For now, it defaults to GTK+ 2, since a newer vala is needed
    to build successfully against GTK+ 3.
    
    https://bugzilla.gnome.org/show_bug.cgi?id=631251

 configure.ac |   21 ++++++++++++++++++++-
 1 files changed, 20 insertions(+), 1 deletions(-)
---
diff --git a/configure.ac b/configure.ac
index 704fb1e..afc89b5 100644
--- a/configure.ac
+++ b/configure.ac
@@ -23,13 +23,32 @@ GTK_DOC_CHECK([1.15])
 # Dependencies
 PKG_CHECK_MODULES(gio, gio-2.0 >= 2.25.16)
 
+AC_MSG_CHECKING([which gtk+ version to compile against])
+AC_ARG_WITH([gtk],
+  [AS_HELP_STRING([--with-gtk=2.0|3.0],[which gtk+ version to compile against (default: 2.0)])],
+  [case "$with_gtk" in
+     2.0|3.0) ;;
+     *) AC_MSG_ERROR([invalid gtk version specified]) ;;
+   esac],
+  [with_gtk=2.0])
+AC_MSG_RESULT([$with_gtk])
+
+case "$with_gtk" in
+  2.0) GTK_API_VERSION=2.0
+       GTK_REQUIRED=2.21.8
+       ;;
+  3.0) GTK_API_VERSION=3.0
+       GTK_REQUIRED=2.90.7
+       ;;
+esac
+
 AC_ARG_ENABLE(editor,
               AC_HELP_STRING([--disable-editor],
                              [Disable the dconf editor]))
 AM_CONDITIONAL(ENABLE_EDITOR, test "x$enable_editor" != "xno")
 
 if test "x$enable_editor" != "xno"; then
-  PKG_CHECK_MODULES(gtk, gtk+-2.0)
+  PKG_CHECK_MODULES(gtk, gtk+-$GTK_API_VERSION >= $GTK_REQUIRED)
   PKG_CHECK_MODULES(libxml, libxml-2.0)
 fi