Fix deadlock when another PDF with an outline is opened

src/gui/sidebar/indextree/SidebarIndexPage.cpp

@@ -47,7 +47,8 @@ SidebarIndexPage::SidebarIndexPage(Control* control, SidebarToolbar* toolbar): A
                                         DOCUMENT_LINKS_COLUMN_PAGE_NUMBER, nullptr);
     g_object_set(G_OBJECT(renderer), "style", PANGO_STYLE_ITALIC, nullptr);
 
-    g_signal_connect(treeViewBookmarks, "cursor-changed", G_CALLBACK(treeBookmarkSelected), this);
+    this->selectHandler = g_signal_connect(treeViewBookmarks, "cursor-changed", G_CALLBACK(treeBookmarkSelected), this);
+    g_assert(this->selectHandler != 0);
 
     gtk_widget_show(this->treeViewBookmarks);
 
@@ -342,11 +343,17 @@ void SidebarIndexPage::documentChanged(DocumentChangeType type) {
 
         Document* doc = this->control->getDocument();
 
+        //  Block the cursor-change signal when the document changes, otherwise
+        //  there will be a deadlock: both the selectHandler and this code will
+        //  lock the document.
+        g_signal_handler_block(this->treeViewBookmarks, this->selectHandler);
         doc->lock();
         GtkTreeModel* model = doc->getContentsModel();
         gtk_tree_view_set_model(GTK_TREE_VIEW(this->treeViewBookmarks), model);
         int count = expandOpenLinks(model, nullptr);
         doc->unlock();
+        g_signal_handler_unblock(this->treeViewBookmarks, this->selectHandler);
+        this->treeBookmarkSelected(this->treeViewBookmarks, this);
 
         hasContents = (count != 0);
     }

src/gui/sidebar/indextree/SidebarIndexPage.h

@@ -105,6 +105,12 @@ private:
      */
     GtkWidget* scrollBookmarks = nullptr;
 
+    /**
+     * Keep track of the tree bookmark selection handler; see documentChanged
+     * method for why this is necessary.
+     */
+    unsigned long selectHandler = 0;  // g_signal_connect uses 0 as error value
+
     /**
      * If currently searching, scroll to the page is disable, else search is not really working
      *