From 68fd6a3f35188669bb392a627857cf8462d57fbd Mon Sep 17 00:00:00 2001
From: Eitan Isaacson <eitan@monotonous.org>
Date: Tue, 6 Oct 2020 17:24:19 +0000
Subject: [PATCH] Bug 1669359 - Fix GeckoTextMarker lesser-than operator.
 r=morgan

Differential Revision: https://phabricator.services.mozilla.com/D92511
---
 accessible/mac/GeckoTextMarker.mm             | 27 +++++++++++++++++++
 .../tests/browser/mac/browser_text_basics.js  | 22 +++++++++++++++
 2 files changed, 49 insertions(+)

diff --git a/accessible/mac/GeckoTextMarker.mm b/accessible/mac/GeckoTextMarker.mm
index 727d4f5e19ad..56369de75542 100644
--- a/accessible/mac/GeckoTextMarker.mm
+++ b/accessible/mac/GeckoTextMarker.mm
@@ -133,6 +133,33 @@ bool GeckoTextMarker::operator<(const GeckoTextMarker& aPoint) const {
     }
   }
 
+  if (pos1 != 0) {
+    // If parents1 is a superset of parents2 then mContainer is a
+    // descendant of aPoint.mContainer. The next element down in parents1
+    // is mContainer's ancestor that is the child of aPoint.mContainer.
+    // We compare its end offset in aPoint.mContainer with aPoint.mOffset.
+    AccessibleOrProxy child = parents1.ElementAt(pos1 - 1);
+    MOZ_ASSERT(child.Parent() == aPoint.mContainer);
+    bool unused;
+    uint32_t endOffset = child.IsProxy() ? child.AsProxy()->EndOffset(&unused)
+                                         : child.AsAccessible()->EndOffset();
+    return endOffset < static_cast<uint32_t>(aPoint.mOffset);
+  }
+
+  if (pos2 != 0) {
+    // If parents2 is a superset of parents1 then aPoint.mContainer is a
+    // descendant of mContainer. The next element down in parents2
+    // is aPoint.mContainer's ancestor that is the child of mContainer.
+    // We compare its start offset in mContainer with mOffset.
+    AccessibleOrProxy child = parents2.ElementAt(pos2 - 1);
+    MOZ_ASSERT(child.Parent() == mContainer);
+    bool unused;
+    uint32_t startOffset = child.IsProxy()
+                               ? child.AsProxy()->StartOffset(&unused)
+                               : child.AsAccessible()->StartOffset();
+    return static_cast<uint32_t>(mOffset) < startOffset;
+  }
+
   MOZ_ASSERT_UNREACHABLE("Broken tree?!");
   return false;
 }
diff --git a/accessible/tests/browser/mac/browser_text_basics.js b/accessible/tests/browser/mac/browser_text_basics.js
index f3b44092f8fb..4999b29f6ec0 100644
--- a/accessible/tests/browser/mac/browser_text_basics.js
+++ b/accessible/tests/browser/mac/browser_text_basics.js
@@ -216,3 +216,25 @@ addAccessibleTask("mac/doc_textmarker_test.html", async (browser, accDoc) => {
 
   testMarkerIntegrity(accDoc, expectedMarkerValues);
 });
+
+// Test text marker lesser-than operator
+addAccessibleTask(
+  `<p id="p">hello <a id="a" href="#">goodbye</a> world</p>`,
+  async (browser, accDoc) => {
+    let macDoc = accDoc.nativeInterface.QueryInterface(
+      Ci.nsIAccessibleMacInterface
+    );
+
+    let start = macDoc.getParameterizedAttributeValue(
+      "AXTextMarkerForIndex",
+      1
+    );
+    let end = macDoc.getParameterizedAttributeValue("AXTextMarkerForIndex", 10);
+
+    let range = macDoc.getParameterizedAttributeValue(
+      "AXTextMarkerRangeForUnorderedTextMarkers",
+      [end, start]
+    );
+    is(stringForRange(macDoc, range), "ello good");
+  }
+);