[tepl] ApplicationWindow: update paste sensitivity according to clipboard

[Sébastien Wilmet <swilmet src gnome org>]

commit 810db09f33837dce39e9fe6b69d7848fc8a44265
Author: Sébastien Wilmet <swilmet gnome org>
Date:   Wed Jul 26 19:44:17 2017 +0200

    ApplicationWindow: update paste sensitivity according to clipboard
    
    I think it is a better implementation than in gedit. We look at all the
    target atoms supported by GtkTextBuffer.
    
    gedit connects to the GtkClipboard::owner-change signal when the
    GtkWindow is realized. But I don't think this is still necessary with
    GTK+ 3. The doc of gtk_widget_get_clipboard() says: “@widget must have a
    GdkDisplay associated with it, so must be attached to a toplevel
    window.”, but here @widget *is* a toplevel window, so I think the
    GdkDisplay is already associated. I've tested and in
    tepl_application_window_constructed(), the GtkApplicationWindow is not
    realized but the GtkClipboard isn't NULL. So I think everything is fine.

 tepl/tepl-application-window.c |  127 ++++++++++++++++++++++++++++++++++++++-
 1 files changed, 123 insertions(+), 4 deletions(-)
---
diff --git a/tepl/tepl-application-window.c b/tepl/tepl-application-window.c
index 1653338..2cec80d 100644
--- a/tepl/tepl-application-window.c
+++ b/tepl/tepl-application-window.c
@@ -187,6 +187,109 @@ select_all_cb (GSimpleAction *action,
        }
 }
 
+/* @can_paste_according_to_clipboard: TRUE if calling
+ * tepl_view_paste_clipboard() will paste something.
+ */
+static void
+set_paste_action_sensitivity_according_to_clipboard (TeplApplicationWindow *tepl_window,
+                                                    gboolean               can_paste_according_to_clipboard)
+{
+       TeplView *view;
+       gboolean view_is_editable = FALSE;
+       GActionMap *action_map;
+       GAction *action;
+
+       view = tepl_tab_group_get_active_view (TEPL_TAB_GROUP (tepl_window));
+
+       if (view != NULL)
+       {
+               view_is_editable = gtk_text_view_get_editable (GTK_TEXT_VIEW (view));
+       }
+
+       action_map = G_ACTION_MAP (tepl_window->priv->gtk_window);
+       action = g_action_map_lookup_action (action_map, "tepl-paste");
+
+       /* Since this is called async, the disposal of the actions may have
+        * already happened. Ensure that we have an action before setting the
+        * state.
+        */
+       if (action != NULL)
+       {
+               g_simple_action_set_enabled (G_SIMPLE_ACTION (action),
+                                            view_is_editable &&
+                                            can_paste_according_to_clipboard);
+       }
+}
+
+static void
+clipboard_targets_received_cb (GtkClipboard *clipboard,
+                              GdkAtom      *atoms,
+                              gint          n_atoms,
+                              gpointer      user_data)
+{
+       TeplApplicationWindow *tepl_window = TEPL_APPLICATION_WINDOW (user_data);
+       TeplBuffer *active_buffer;
+       GtkTargetList *target_list;
+       gboolean can_paste = FALSE;
+       gint i;
+
+       active_buffer = tepl_tab_group_get_active_buffer (TEPL_TAB_GROUP (tepl_window));
+       if (active_buffer == NULL)
+       {
+               goto end;
+       }
+
+       target_list = gtk_text_buffer_get_paste_target_list (GTK_TEXT_BUFFER (active_buffer));
+
+       for (i = 0; i < n_atoms; i++)
+       {
+               if (gtk_target_list_find (target_list, atoms[i], NULL))
+               {
+                       can_paste = TRUE;
+                       break;
+               }
+       }
+
+end:
+       set_paste_action_sensitivity_according_to_clipboard (tepl_window, can_paste);
+
+       /* Async operation finished. */
+       g_object_unref (tepl_window->priv->gtk_window);
+}
+
+/* How to test this easily: with a clipboard manager like xsel:
+ * $ xsel --clipboard --clear
+ * $ echo -n "bloum!" | xsel --clipboard # -> GdkAtom "TEXT"
+ * Copy text in a GtkTextBuffer -> GdkAtom "GTK_TEXT_BUFFER_CONTENTS"
+ */
+static void
+update_paste_action_sensitivity (TeplApplicationWindow *tepl_window)
+{
+       GtkClipboard *clipboard;
+       GdkDisplay *display;
+
+       clipboard = gtk_widget_get_clipboard (GTK_WIDGET (tepl_window->priv->gtk_window),
+                                             GDK_SELECTION_CLIPBOARD);
+       g_return_if_fail (clipboard != NULL);
+
+       display = gtk_clipboard_get_display (clipboard);
+       if (!gdk_display_supports_selection_notification (display))
+       {
+               /* Do as if it can always paste, because if we set the paste
+                * action as insensitive, we won't get the notification when the
+                * clipboard contains something that we can paste (i.e.
+                * clipboard_owner_change_cb() will not be called).
+                */
+               set_paste_action_sensitivity_according_to_clipboard (tepl_window, TRUE);
+               return;
+       }
+
+       g_object_ref (tepl_window->priv->gtk_window);
+       gtk_clipboard_request_targets (clipboard,
+                                      clipboard_targets_received_cb,
+                                      tepl_window);
+}
+
 static void
 update_edit_actions_sensitivity (TeplApplicationWindow *tepl_window)
 {
@@ -220,10 +323,8 @@ update_edit_actions_sensitivity (TeplApplicationWindow *tepl_window)
        g_simple_action_set_enabled (G_SIMPLE_ACTION (action),
                                     buffer_has_selection);
 
-       /* TODO see if the clipboard isn't empty. */
-       action = g_action_map_lookup_action (action_map, "tepl-paste");
-       g_simple_action_set_enabled (G_SIMPLE_ACTION (action),
-                                    buffer != NULL);
+       /* For tepl-paste: */
+       update_paste_action_sensitivity (tepl_window);
 
        action = g_action_map_lookup_action (action_map, "tepl-delete");
        g_simple_action_set_enabled (G_SIMPLE_ACTION (action),
@@ -330,9 +431,18 @@ tepl_application_window_set_property (GObject      *object,
 }
 
 static void
+clipboard_owner_change_cb (GtkClipboard          *clipboard,
+                          GdkEvent              *event,
+                          TeplApplicationWindow *tepl_window)
+{
+       update_paste_action_sensitivity (tepl_window);
+}
+
+static void
 tepl_application_window_constructed (GObject *object)
 {
        TeplApplicationWindow *tepl_window = TEPL_APPLICATION_WINDOW (object);
+       GtkClipboard *clipboard;
 
        if (G_OBJECT_CLASS (tepl_application_window_parent_class)->constructed != NULL)
        {
@@ -340,6 +450,15 @@ tepl_application_window_constructed (GObject *object)
        }
 
        add_actions (tepl_window);
+
+       clipboard = gtk_widget_get_clipboard (GTK_WIDGET (tepl_window->priv->gtk_window),
+                                             GDK_SELECTION_CLIPBOARD);
+
+       g_signal_connect_object (clipboard,
+                                "owner-change",
+                                G_CALLBACK (clipboard_owner_change_cb),
+                                tepl_window,
+                                0);
 }
 
 static void