tor-browser

commit 29f0c3cd54d66cefd2a7899060b02a7c603b01eb
parent 2f990aab82f1973c1168a56b6c51fc229d1604f3
Author: Botond Ballo <botond@mozilla.com>
Date:   Tue, 25 Nov 2025 04:50:45 +0000

Bug 2001862 - Introduce ActiveScrolledRoot::LowestCommonAncestor. r=mstange

Differential Revision: https://phabricator.services.mozilla.com/D273758

Diffstat:
M
layout/painting/nsDisplayList.h
 | 
24
++++++++++++++++++++++++

1 file changed, 24 insertions(+), 0 deletions(-)
diff --git a/layout/painting/nsDisplayList.h b/layout/painting/nsDisplayList.h
@@ -199,6 +199,30 @@ struct ActiveScrolledRoot {
     return Depth(aOne) <= Depth(aTwo) ? aOne : aTwo;
   }
 
+  static const ActiveScrolledRoot* LowestCommonAncestor(
+      const ActiveScrolledRoot* aOne, const ActiveScrolledRoot* aTwo) {
+    uint32_t depth1 = Depth(aOne);
+    uint32_t depth2 = Depth(aTwo);
+    if (depth1 > depth2) {
+      for (uint32_t i = 0; i < (depth1 - depth2); ++i) {
+        MOZ_ASSERT(aOne);
+        aOne = aOne->mParent;
+      }
+    } else if (depth1 < depth2) {
+      for (uint32_t i = 0; i < (depth2 - depth1); ++i) {
+        MOZ_ASSERT(aTwo);
+        aTwo = aTwo->mParent;
+      }
+    }
+    while (aOne != aTwo) {
+      MOZ_ASSERT(aOne);
+      MOZ_ASSERT(aTwo);
+      aOne = aOne->mParent;
+      aTwo = aTwo->mParent;
+    }
+    return aOne;
+  }
+
   static const ActiveScrolledRoot* PickDescendant(
       const ActiveScrolledRoot* aOne, const ActiveScrolledRoot* aTwo) {
     MOZ_ASSERT(IsAncestor(aOne, aTwo) || IsAncestor(aTwo, aOne));