[evince] toolbar: Provide hint when find is unavailable

[Germán Poo-Caamaño <gpoo src gnome org>]

commit 9ead605ab67c81c1847361bf9ffefce6fd32b792
Author: Germán Poo-Caamaño <gpoo gnome org>
Date:   Fri Jul 13 00:03:49 2018 -0400

    toolbar: Provide hint when find is unavailable
    
    When document type does not support 'find', Evince disables the
    find feature. To provide a hint why 'find' is disabled, we state
    the reason in the tooltip.
    
    Fixes #105

 shell/ev-toolbar.c | 22 ++++++++++++++++++++--
 1 file changed, 20 insertions(+), 2 deletions(-)
---
diff --git a/shell/ev-toolbar.c b/shell/ev-toolbar.c
index b0c2b3c8..a9b7dbec 100644
--- a/shell/ev-toolbar.c
+++ b/shell/ev-toolbar.c
@@ -84,7 +84,8 @@ ev_toolbar_set_button_action (EvToolbar   *ev_toolbar,
         gtk_actionable_set_action_name (GTK_ACTIONABLE (button), action_name);
         gtk_button_set_label (button, NULL);
         gtk_button_set_focus_on_click (button, FALSE);
-        gtk_widget_set_tooltip_text (GTK_WIDGET (button), tooltip);
+        if (tooltip)
+                gtk_widget_set_tooltip_text (GTK_WIDGET (button), tooltip);
 }
 
 static GtkWidget *
@@ -177,6 +178,19 @@ ev_toolbar_sidebar_current_page_changed (EvSidebar  *ev_sidebar,
         g_free (icon_name);
 }
 
+static void
+ev_toolbar_find_button_sensitive_changed (GtkWidget  *find_button,
+                                         GParamSpec *pspec,
+                                         EvToolbar *ev_toolbar)
+{
+        if (gtk_widget_is_sensitive (find_button))
+                gtk_widget_set_tooltip_text (find_button,
+                                             _("Find a word or phrase in the document"));
+        else
+                gtk_widget_set_tooltip_text (find_button,
+                                             _("Search not available for this document"));
+}
+
 static void
 ev_toolbar_constructed (GObject *object)
 {
@@ -244,9 +258,13 @@ ev_toolbar_constructed (GObject *object)
 
         /* Find */
         button = ev_toolbar_create_toggle_button (ev_toolbar, "win.toggle-find", "edit-find-symbolic",
-                                                  _("Find a word or phrase in the document"));
+                                                  NULL);
         ev_toolbar->priv->find_button = button;
         gtk_header_bar_pack_end (GTK_HEADER_BAR (ev_toolbar), button);
+        g_signal_connect (button,
+                          "notify::sensitive",
+                          G_CALLBACK (ev_toolbar_find_button_sensitive_changed),
+                          ev_toolbar);
 
         g_object_unref (builder);
 }