1 files changed, 49 insertions, 0 deletions
diff --git a/layout/generic/nsSelection.cpp b/layout/generic/nsSelection.cpp
index 3f8d11b486..301d799525 100644
--- a/layout/generic/nsSelection.cpp
+++ b/layout/generic/nsSelection.cpp
@@ -6434,6 +6434,55 @@ Selection::Modify(const nsAString& aAlter, const nsAString& aDirection,
   }
 }
 
+void
+Selection::SetBaseAndExtent(nsINode& aAnchorNode, uint32_t aAnchorOffset,
+                            nsINode& aFocusNode, uint32_t aFocusOffset,
+                            ErrorResult& aRv)
+{
+  if (!mFrameSelection) {
+    return;
+  }
+
+  SelectionBatcher batch(this);
+
+  int32_t relativePosition =
+    nsContentUtils::ComparePoints(&aAnchorNode, aAnchorOffset,
+                                  &aFocusNode, aFocusOffset);
+  nsINode* start = &aAnchorNode;
+  nsINode* end = &aFocusNode;
+  uint32_t startOffset = aAnchorOffset;
+  uint32_t endOffset = aFocusOffset;
+  if (relativePosition > 0) {
+    start = &aFocusNode;
+    end = &aAnchorNode;
+    startOffset = aFocusOffset;
+    endOffset = aAnchorOffset;
+  }
+
+  RefPtr<nsRange> newRange;
+  nsresult rv = nsRange::CreateRange(start, startOffset, end, endOffset,
+                                     getter_AddRefs(newRange));
+  // CreateRange returns IndexSizeError if any offset is out of bounds.
+  if (NS_FAILED(rv)) {
+    aRv.Throw(rv);
+    return;
+  }
+
+  rv = RemoveAllRanges();
+  if (NS_FAILED(rv)) {
+    aRv.Throw(rv);
+    return;
+  }
+
+  rv = AddRange(newRange);
+  if (NS_FAILED(rv)) {
+    aRv.Throw(rv);
+    return;
+  }
+
+  SetDirection(relativePosition > 0 ? eDirPrevious : eDirNext);
+}
+
 /** SelectionLanguageChange modifies the cursor Bidi level after a change in keyboard direction
  *  @param aLangRTL is true if the new language is right-to-left or false if the new language is left-to-right
  */