[geary] Workaround occasional crash when removing messages with nested tables.

[Michael Gratton <mjog src gnome org>]

commit 36a35f985fe1aa82ef2a448c0a216796252fdf39
Author: Michael James Gratton <mike vee net>
Date:   Tue Aug 9 21:36:29 2016 +1000

    Workaround occasional crash when removing messages with nested tables.
    
    WebKitGTK+ will occasionally crash when removing a node from the document
    that has nested tables as descendants and the nested table's cells have
    borders. Removing the nested table's cell's children depth-first in
    reverse order will avoid triggering the bug. See Bug 769010.
    
    Bug 769010.

 .../conversation-viewer/conversation-viewer.vala   |   30 +++++++++++++++++++-
 1 files changed, 29 insertions(+), 1 deletions(-)
---
diff --git a/src/client/conversation-viewer/conversation-viewer.vala 
b/src/client/conversation-viewer/conversation-viewer.vala
index 95ec418..7cac33d 100644
--- a/src/client/conversation-viewer/conversation-viewer.vala
+++ b/src/client/conversation-viewer/conversation-viewer.vala
@@ -324,6 +324,7 @@ public class ConversationViewer : Gtk.Box {
         // Remove all messages from DOM.
         try {
             foreach (WebKit.DOM.HTMLElement element in email_to_element.values) {
+                remove_tables_safely(element);
                 if (element.get_parent_element() != null)
                     element.get_parent_element().remove_child(element);
             }
@@ -2133,6 +2134,7 @@ public class ConversationViewer : Gtk.Box {
         email_to_element.unset(email.id);
         
         try {
+            remove_tables_safely(element);
             if (element.get_parent_element() != null)
                 element.get_parent_element().remove_child(element);
         } catch (Error err) {
@@ -2515,5 +2517,31 @@ public class ConversationViewer : Gtk.Box {
         return current_folder != null && current_folder.special_folder_type
             == Geary.SpecialFolderType.DRAFTS;
     }
-}
 
+    // Workaround for occasional WebKitGTK+ crash when removing a node
+    // from the document that has nested tables as descendants and the
+    // nested table's cells have borders. Removing the nested table's
+    // cell's children depth-first in reverse order will avoid
+    // triggering the bug. See Bug 769010.
+    private void remove_tables_safely(WebKit.DOM.Node element) throws Error {
+        WebKit.DOM.HTMLElement nested_table =
+            Util.DOM.select(element, "table table");
+        while (nested_table != null) {
+            remove_children_reversed(nested_table);
+            if (nested_table.parent_node != null) {
+                nested_table.parent_node.remove_child(nested_table);
+            }
+            nested_table = Util.DOM.select(element, "table table");
+        }
+    }
+
+    private inline void remove_children_reversed(WebKit.DOM.Node element)
+        throws Error {
+        WebKit.DOM.Node child = element.last_child;
+        while (child != null) {
+            remove_children_reversed(child);
+            element.remove_child(child);
+            child = element.last_child;
+        }
+    }
+}