GtkSearchEntry: Delay the changed signal by default

Emit the "changed" signal after 150 msecs, so that searching
through big lists, or doing online searches feels more responsive.

This is something already done in various applications to make
search-as-you type more responsive (gnome-shell, gnome-documents,
gnome-control-center, etc.). The 150 msecs is the value currently
used by gnome-shell, so keep it (invisibly) consistent.

https://bugzilla.gnome.org/show_bug.cgi?id=700229

demos/gtk-demo/Makefile.am

@@ -42,6 +42,7 @@ demos =						\
 	revealer.c				\
 	rotated_text.c				\
 	search_entry.c				\
+	search_entry2.c				\
 	sizegroup.c				\
 	spinner.c				\
 	stack.c					\

demos/gtk-demo/demo.gresource.xml

@@ -116,6 +116,7 @@
     <file>revealer.c</file>
     <file>rotated_text.c</file>
     <file>search_entry.c</file>
+    <file>search_entry2.c</file>
     <file>sizegroup.c</file>
     <file>stack.c</file>
     <file>spinner.c</file>

demos/gtk-demo/search_entry2.c

@@ -0,0 +1,96 @@
+/* Entry/Delayed Search Entry
+ *
+ * GtkSearchEntry sets up GtkEntries ready for search. Search entries
+ * have their "changed" signal delayed and should be used
+ * when the searched operation is slow such as loads of entries
+ * to search, or online searches.
+ */
+
+#include <gtk/gtk.h>
+
+static GtkWidget *window = NULL;
+
+static void
+search_entry_destroyed (GtkWidget  *widget)
+{
+  window = NULL;
+}
+
+static void
+search_changed_cb (GtkSearchEntry *entry,
+                   GtkLabel       *result_label)
+{
+  const char *text;
+  text = gtk_entry_get_text (GTK_ENTRY (entry));
+  g_message ("search changed: %s", text);
+  gtk_label_set_text (result_label, text ? text : "");
+}
+
+GtkWidget *
+do_search_entry2 (GtkWidget *do_widget)
+{
+  GtkWidget *content_area;
+  GtkWidget *vbox;
+  GtkWidget *hbox;
+  GtkWidget *label;
+  GtkWidget *entry;
+  GtkWidget *button;
+
+  if (!window)
+    {
+      window = gtk_dialog_new_with_buttons ("Search Entry #2",
+                                            GTK_WINDOW (do_widget),
+                                            0,
+                                            GTK_STOCK_CLOSE,
+                                            GTK_RESPONSE_NONE,
+                                            NULL);
+      gtk_window_set_resizable (GTK_WINDOW (window), FALSE);
+
+      g_signal_connect (window, "response",
+                        G_CALLBACK (gtk_widget_destroy), NULL);
+      g_signal_connect (window, "destroy",
+                        G_CALLBACK (search_entry_destroyed), &window);
+
+      content_area = gtk_dialog_get_content_area (GTK_DIALOG (window));
+
+      vbox = gtk_box_new (GTK_ORIENTATION_VERTICAL, 5);
+      gtk_box_pack_start (GTK_BOX (content_area), vbox, TRUE, TRUE, 0);
+      gtk_container_set_border_width (GTK_CONTAINER (vbox), 5);
+
+      label = gtk_label_new (NULL);
+      gtk_label_set_markup (GTK_LABEL (label), "Search entry demo #2");
+      gtk_box_pack_start (GTK_BOX (vbox), label, FALSE, FALSE, 0);
+
+      /* Create our entry */
+      entry = gtk_search_entry_new ();
+      gtk_box_pack_start (GTK_BOX (vbox), entry, FALSE, FALSE, 0);
+
+      /* Result */
+      hbox = gtk_box_new (GTK_ORIENTATION_HORIZONTAL, 10);
+      gtk_box_pack_start (GTK_BOX (vbox), hbox, TRUE, TRUE, 0);
+      gtk_container_set_border_width (GTK_CONTAINER (hbox), 0);
+
+      label = gtk_label_new ("Result:");
+      gtk_box_pack_start (GTK_BOX (hbox), label, TRUE, TRUE, 0);
+
+      label = gtk_label_new ("");
+      gtk_box_pack_start (GTK_BOX (hbox), label, TRUE, TRUE, 0);
+
+      g_signal_connect (entry, "changed",
+                        G_CALLBACK (search_changed_cb), label);
+
+      /* Give the focus to the close button */
+      button = gtk_dialog_get_widget_for_response (GTK_DIALOG (window), GTK_RESPONSE_NONE);
+      gtk_widget_grab_focus (button);
+    }
+
+  if (!gtk_widget_get_visible (window))
+    gtk_widget_show_all (window);
+  else
+    {
+      gtk_widget_destroy (window);
+      window = NULL;
+    }
+
+  return window;
+}