Bug 1679075 - Don't go past empty input field in HyperTextIterator::Next. r=morgan

The normalize function was putting the current container/offset past the end boundary. This caused overruns with getting the text for the range of the input object, and some unexpected invalid ranges.

Differential Revision: https://phabricator.services.mozilla.com/D98236

accessible/mac/HyperTextAccessibleWrap.mm

@@ -79,6 +79,12 @@ bool HyperTextIterator::NormalizeForward() {
       mCurrentContainer = mCurrentContainer->Parent()->AsHyperText();
       mCurrentStartOffset = endOffset;
 
+      if (mCurrentContainer == mEndContainer &&
+          mCurrentStartOffset >= mEndOffset) {
+        // Reached end boundary.
+        return false;
+      }
+
       // Call NormalizeForward recursively to get top-most link if at the end of
       // one, or innermost link if at the beginning.
       NormalizeForward();
@@ -98,6 +104,12 @@ bool HyperTextIterator::NormalizeForward() {
         mCurrentStartOffset = 0;
       }
 
+      if (mCurrentContainer == mEndContainer &&
+          mCurrentStartOffset >= mEndOffset) {
+        // Reached end boundary.
+        return false;
+      }
+
       // Call NormalizeForward recursively to get top-most embedding ancestor
       // if at the end of one, or innermost link if at the beginning.
       NormalizeForward();

accessible/mac/mozTextAccessible.mm

@@ -171,10 +171,8 @@ inline NSString* ToNSString(id aValue) {
     return nil;
   }
 
-  GeckoTextMarker startMarker =
-      GeckoTextMarker::MarkerFromIndex(mGeckoAccessible, 0);
-
-  GeckoTextMarkerRange fromStartToSelection(startMarker, selection.mStart);
+  GeckoTextMarkerRange fromStartToSelection(
+      GeckoTextMarker(mGeckoAccessible, 0), selection.mStart);
 
   return [NSValue valueWithRange:NSMakeRange(fromStartToSelection.Length(),
                                              selection.Length())];
@@ -268,6 +266,10 @@ inline NSString* ToNSString(id aValue) {
 - (NSString*)moxStringForRange:(NSValue*)range {
   GeckoTextMarkerRange markerRange = [self textMarkerRangeFromRange:range];
 
+  if (!markerRange.IsValid()) {
+    return nil;
+  }
+
   return markerRange.Text();
 }
 

accessible/tests/browser/mac/browser_text_basics.js

@@ -245,3 +245,21 @@ addAccessibleTask(
     is(stringForRange(macDoc, range), "ello good");
   }
 );
+
+addAccessibleTask(
+  `<input id="input" value=""><a href="#">goodbye</a>`,
+  async (browser, accDoc) => {
+    let macDoc = accDoc.nativeInterface.QueryInterface(
+      Ci.nsIAccessibleMacInterface
+    );
+
+    let input = getNativeInterface(accDoc, "input");
+
+    let range = macDoc.getParameterizedAttributeValue(
+      "AXTextMarkerRangeForUIElement",
+      input
+    );
+
+    is(stringForRange(macDoc, range), "", "string value is correct");
+  }
+);