gtk3-demo: Add a page setup example

This mainly so I can fix deprecation warnings in the
page setup dialog.

demos/gtk-demo/Makefile.am

@@ -61,6 +61,10 @@ demos =						\
 	transparent.c				\
 	tree_store.c
 
+if OS_UNIX
+demos += pagesetup.c
+endif
+
 AM_CPPFLAGS = \
 	-I$(top_srcdir) 			\
 	-I$(top_builddir)/gdk			\

demos/gtk-demo/demo.gresource.xml

@@ -147,6 +147,7 @@
     <file>offscreen_window.c</file>
     <file>offscreen_window2.c</file>
     <file>overlay.c</file>
+    <file>pagesetup.c</file>
     <file>panes.c</file>
     <file>pickers.c</file>
     <file>pixbufs.c</file>

demos/gtk-demo/pagesetup.c

@@ -0,0 +1,38 @@
+/* Printing/Page Setup
+ *
+ * GtkPageSetupUnixDialog can be used if page setup is needed
+ * independent of a full printing dialog.
+ */
+
+#include <math.h>
+#include <gtk/gtk.h>
+#include <gtk/gtkunixprint.h>
+
+static void
+done_cb (GtkDialog *dialog, gint response, gpointer data)
+{
+  gtk_widget_destroy (GTK_WIDGET (dialog));
+}
+
+GtkWidget *
+do_pagesetup (GtkWidget *do_widget)
+{
+  static GtkWidget *window = NULL;
+
+  if (!window)
+    {
+      window = gtk_page_setup_unix_dialog_new ("Page Setup", GTK_WINDOW (do_widget));
+      g_signal_connect (window, "destroy", G_CALLBACK (gtk_widget_destroyed), &window);
+      g_signal_connect (window, "response", G_CALLBACK (done_cb), NULL);
+    }
+
+  if (!gtk_widget_get_visible (window))
+    gtk_widget_show (window);
+  else
+    {
+      gtk_widget_destroy (window);
+      window = NULL;
+    }
+
+  return window;
+}

demos/gtk-demo/printing.c

@@ -1,4 +1,4 @@
-/* Printing
+/* Printing/Printing
  *
  * GtkPrintOperation offers a simple API to support printing
  * in a cross-platform way.