Dom text scanner fixes (#505)

* Fix test case

* Add test-dom-text-scanner

* Ensure that DOMTextScanner._node never becomes null

* Add remainder

1 files changed, 14 insertions, 1 deletions

diff --git a/ext/fg/js/dom-text-scanner.js b/ext/fg/js/dom-text-scanner.js
index 2de65041..8fa67ede 100644
--- a/ext/fg/js/dom-text-scanner.js
+++ b/ext/fg/js/dom-text-scanner.js
@@ -60,6 +60,15 @@ class DOMTextScanner {
     }
 
     /**
+     * Gets the remaining number of characters that weren't scanned in the last seek() call.
+     * This value is usually 0 unless the end of the document was reached.
+     * @returns An integer.
+     */
+    get remainder() {
+        return this._remainder;
+    }
+
+    /**
      * Gets the accumulated content string resulting from calls to seek().
      * @returns A string.
      */
@@ -85,6 +94,7 @@ class DOMTextScanner {
 
         const generateLayoutContent = this._generateLayoutContent;
         let node = this._node;
+        let lastNode = node;
         let resetOffset = this._resetOffset;
         let newlines = 0;
         while (node !== null) {
@@ -92,6 +102,7 @@ class DOMTextScanner {
             const nodeType = node.nodeType;
 
             if (nodeType === TEXT_NODE) {
+                lastNode = node;
                 if (!(
                     forward ?
                     this._seekTextNodeForward(node, resetOffset) :
@@ -101,6 +112,8 @@ class DOMTextScanner {
                     break;
                 }
             } else if (nodeType === ELEMENT_NODE) {
+                lastNode = node;
+                this._offset = 0;
                 [enterable, newlines] = DOMTextScanner.getElementSeekInfo(node);
                 if (newlines > this._newlines && generateLayoutContent) {
                     this._newlines = newlines;
@@ -121,7 +134,7 @@ class DOMTextScanner {
             resetOffset = true;
         }
 
-        this._node = node;
+        this._node = lastNode;
         this._resetOffset = resetOffset;
 
         return this;