Only load pages when their tab is switched to upon session restore

Firefox has led the way implementing this behaviour to improve the experience
of restoring a session with lots of tabs. By delaying the loading of pages to
when the user shows interest in them, the time it takes for the browser to
become usable is diminished, and less pages are loaded in parallel, which
improves load time for the first pages the user sees.

It also has the advante of displaying less HTTP Basic Auth dialogs, when the
user has many tabs pointed to the same server.

https://bugzilla.gnome.org/show_bug.cgi?id=675302

1 files changed, 96 insertions, 5 deletions

diff --git a/embed/ephy-embed.c b/embed/ephy-embed.c
index 5d9f631bd..8ead506a5 100644
--- a/embed/ephy-embed.c
+++ b/embed/ephy-embed.c
@@ -43,13 +43,15 @@
 #include <webkit/webkit.h>
 #endif
 
-static void     ephy_embed_constructed      (GObject *object);
+static void     ephy_embed_constructed         (GObject *object);
 #ifndef HAVE_WEBKIT2
-static gboolean ephy_embed_inspect_show_cb  (WebKitWebInspector *inspector,
-                                             EphyEmbed *embed);
-static gboolean ephy_embed_inspect_close_cb (WebKitWebInspector *inspector,
-                                             EphyEmbed *embed);
+static gboolean ephy_embed_inspect_show_cb     (WebKitWebInspector *inspector,
+                                                EphyEmbed *embed);
+static gboolean ephy_embed_inspect_close_cb    (WebKitWebInspector *inspector,
+                                                EphyEmbed *embed);
 #endif
+static void     ephy_embed_restored_window_cb  (EphyEmbedShell *shell,
+                                                EphyEmbed *embed);
 
 #define EPHY_EMBED_GET_PRIVATE(object)(G_TYPE_INSTANCE_GET_PRIVATE ((object), EPHY_TYPE_EMBED, EphyEmbedPrivate))
 
@@ -79,6 +81,8 @@ struct _EphyEmbedPrivate
   GtkWidget *fullscreen_message_label;
   char *fullscreen_string;
 
+  WebKitNetworkRequest *delayed_request;
+
   GtkWidget *overview;
   guint overview_mode : 1;
   GSList *messages;
@@ -415,6 +419,8 @@ ephy_embed_dispose (GObject *object)
     priv->adblock_handler_id = 0;
   }
 
+  g_clear_object (&priv->delayed_request);
+
   G_OBJECT_CLASS (ephy_embed_parent_class)->dispose (object);
 }
 
@@ -423,8 +429,11 @@ ephy_embed_finalize (GObject *object)
 {
   EphyEmbed *embed = EPHY_EMBED (object);
   EphyEmbedPrivate *priv = embed->priv;
+  EphyEmbedShell *shell = ephy_embed_shell_get_default ();
   GSList *list;
 
+  g_signal_handlers_disconnect_by_func(shell, ephy_embed_restored_window_cb, embed);
+
   list = priv->destroy_on_transition_list;
   for (; list; list = list->next) {
     GtkWidget *widget = GTK_WIDGET (list->data);
@@ -862,10 +871,50 @@ setup_adblock (GSettings *settings,
 #endif
 
 static void
+ephy_embed_maybe_load_delayed_request (EphyEmbed *embed)
+{
+  EphyEmbedPrivate *priv = embed->priv;
+  EphyWebView *web_view;
+
+  if (!priv->delayed_request)
+    return;
+
+  web_view = ephy_embed_get_web_view (embed);
+
+  ephy_web_view_load_request (web_view, priv->delayed_request);
+  g_clear_object (&priv->delayed_request);
+
+  /* This is to allow UI elements watching load status to show that the page is
+   * loading as soon as possible.
+   */
+#ifdef HAVE_WEBKIT2
+  g_signal_emit_by_name (web_view, "load-changed", WEBKIT_LOAD_STARTED);
+#else
+  g_object_notify (G_OBJECT (web_view), "load-status");
+#endif
+}
+
+static void
+ephy_embed_restored_window_cb (EphyEmbedShell *shell, EphyEmbed *embed)
+{
+  if (!gtk_widget_get_mapped (GTK_WIDGET (embed)))
+    return;
+
+  ephy_embed_maybe_load_delayed_request (embed);
+}
+
+static void
+ephy_embed_mapped_cb (GtkWidget *widget, gpointer data)
+{
+  ephy_embed_maybe_load_delayed_request ((EphyEmbed*)widget);
+}
+
+static void
 ephy_embed_constructed (GObject *object)
 {
   EphyEmbed *embed = (EphyEmbed*)object;
   EphyEmbedPrivate *priv = embed->priv;
+  EphyEmbedShell *shell = ephy_embed_shell_get_default ();
 #ifndef HAVE_WEBKIT2
   GtkWidget *scrolled_window;
 #endif
@@ -879,6 +928,12 @@ ephy_embed_constructed (GObject *object)
   WebKitWebInspector *inspector;
   GtkWidget *overlay;
 
+  g_signal_connect (shell, "window-restored",
+                    G_CALLBACK (ephy_embed_restored_window_cb), embed);
+
+  g_signal_connect (embed, "map",
+                    G_CALLBACK (ephy_embed_mapped_cb), NULL);
+
   /* Skeleton */
   web_view = WEBKIT_WEB_VIEW (ephy_web_view_new ());
 #ifndef HAVE_WEBKIT2
@@ -1161,6 +1216,42 @@ ephy_embed_get_overview_mode (EphyEmbed *embed)
 }
 
 /**
+ * ephy_embed_set_delayed_load_request:
+ * @embed: a #EphyEmbed
+ * @request: a #WebKitNetworkRequest
+ *
+ * Sets the #WebKitNetworkRequest that should be loaded when the tab this embed
+ * is on is switched to.
+ */
+void
+ephy_embed_set_delayed_load_request (EphyEmbed *embed, WebKitNetworkRequest *request)
+{
+  g_return_if_fail (EPHY_IS_EMBED (embed));
+  g_return_if_fail (WEBKIT_IS_NETWORK_REQUEST (request));
+
+  g_clear_object (&embed->priv->delayed_request);
+
+  g_object_ref (request);
+  embed->priv->delayed_request = request;
+}
+
+/**
+ * ephy_embed_has_load_pending:
+ * @embed: a #EphyEmbed
+ *
+ * Checks whether a load has been delayed for this #EphyEmbed.
+ *
+ * Returns: %TRUE or %FALSE
+ */
+gboolean
+ephy_embed_has_load_pending (EphyEmbed *embed)
+{
+  g_return_val_if_fail (EPHY_IS_EMBED (embed), FALSE);
+
+  return !!embed->priv->delayed_request;
+}
+
+/**
  * ephy_embed_get_overview:
  * @embed: a #EphyEmbed
  *