[geary/wip/geary-is-descendant-of: 3/3] Fix select-quoting not preserving newlines in some cases

[Michael Gratton <mjog src gnome org>]

commit 6d96fee5d0775300c1943d9222c870695fdab062
Author: Michael Gratton <mike vee net>
Date:   Sat Feb 2 14:48:22 2019 +1100

    Fix select-quoting not preserving newlines in some cases
    
    If the common ancestor of the quoted text is the plain-text-message DIV
    itself, the isDescendant test fails and the style to preserve new lines
    is not maintained. This adds a non-strict check to isDescendant and
    enables that when checking the common ancestor node.

 ui/conversation-web-view.js | 29 ++++++++++++++++++-----------
 1 file changed, 18 insertions(+), 11 deletions(-)
---
diff --git a/ui/conversation-web-view.js b/ui/conversation-web-view.js
index fb6d9aca..ef209223 100644
--- a/ui/conversation-web-view.js
+++ b/ui/conversation-web-view.js
@@ -201,12 +201,15 @@ ConversationPageState.prototype = {
                 ancestor = ancestor.parentNode;
             }
 
-            // If the selection is part of a plain text message,
-            // we have to stick it in an appropriately styled div,
-            // so that new lines are preserved.
+            // If the selection is part of a plain text message, we
+            // have to stick it in an appropriately styled div, so
+            // that new lines are preserved. Do a non-strict ancestor
+            // check since the common ancestor may well be the plain
+            // text DIV itself
             let dummy = document.createElement("DIV");
             let includeDummy = false;
-            if (ConversationPageState.isDescendantOf(ancestor, "DIV", "plaintext")) {
+            if (ConversationPageState.isDescendantOf(
+                ancestor, "DIV", "plaintext", false)) {
                 dummy.classList.add("plaintext");
                 dummy.setAttribute("style", "white-space: pre-wrap;");
                 includeDummy = true;
@@ -324,17 +327,21 @@ ConversationPageState.isDeceptiveText = function(text, href) {
 /**
  * See if this element has an ancestor with the given tag and class.
  *
- * ancestorTag must be all uppercase.
+ * The value of ancestorTag must be all uppercase.
  *
  * If ancestorClass is null, no class checking is done.
+ * If strict is is true, the given node will not be checked.
  */
-ConversationPageState.isDescendantOf = function(node, ancestorTag, ancestorClass = null) {
-    let ancestor = node.parentNode;
+ConversationPageState.isDescendantOf = function(node,
+                                                ancestorTag,
+                                                ancestorClass = null,
+                                                strict = true) {
+    let ancestor = strict ? node.parentNode : node;
     while (ancestor != null) {
-        if (ancestor.nodeName.toUpperCase() == ancestorTag) {
-            if (!ancestorClass || ancestor.classList.contains(ancestorClass)) {
-                return true;
-            }
+        if (ancestor.nodeName.toUpperCase() == ancestorTag &&
+            (ancestorClass == null ||
+             ancestor.classList.contains(ancestorClass))) {
+            return true;
         }
         ancestor = ancestor.parentNode;
     }