tor-browser

commit 834918e43e386947cdaae2e5b93d5b96f51f7232
parent 2b0a69fb37e3a360ca89497ce8bd3cfef15c9bc2
Author: Ting-Yu Lin <tlin@mozilla.com>
Date:   Tue, 11 Nov 2025 18:03:02 +0000

Bug 1999366 - Use block frame's writing-mode to construct absolute containing block rect. r=layout-reviewers,dholbert

The motivation is:
1. The `parentWM` is misleading, because the parent frame can create
   `ReflowOutput` with this block frame's writing-mode, e.g. flex container did
   this [1].

2. If this block frame is fragmented, to get the correct cb rect, we'll have to
   apply the skip side for the border, which operates on this block's
   writing-mode. This will be done in bug 1994083.

3. This does not change behavior, because we only use physical `containingBlock`
   as the parameter to `AbsoluteContainingBlock::Reflow()`.

[1] https://searchfox.org/firefox-main/rev/931471037b8a4f16ce3ccfa864310540cac255c1/layout/generic/nsFlexContainerFrame.cpp#6431

Differential Revision: https://phabricator.services.mozilla.com/D272075

Diffstat:
M
layout/generic/nsBlockFrame.cpp
 | 
10
++++------

1 file changed, 4 insertions(+), 6 deletions(-)
diff --git a/layout/generic/nsBlockFrame.cpp b/layout/generic/nsBlockFrame.cpp
@@ -1645,7 +1645,6 @@ void nsBlockFrame::Reflow(nsPresContext* aPresContext, ReflowOutput& aMetrics,
   // resetting the size. Because of this, we must not reflow our abs-pos
   // children in that situation --- what we think is our "new size" will not be
   // our real new size. This also happens to be more efficient.
-  WritingMode parentWM = aMetrics.GetWritingMode();
   if (HasAbsolutelyPositionedChildren()) {
     AbsoluteContainingBlock* absoluteContainer = GetAbsoluteContainingBlock();
     bool haveInterrupt = aPresContext->HasPendingInterrupt();
@@ -1695,9 +1694,8 @@ void nsBlockFrame::Reflow(nsPresContext* aPresContext, ReflowOutput& aMetrics,
           aMetrics.Height() != oldSize.height;
 
       const LogicalRect containingBlock = [&]() {
-        LogicalRect rect{parentWM, LogicalPoint{parentWM},
-                         aMetrics.Size(parentWM)};
-        rect.Deflate(parentWM, aReflowInput.ComputedLogicalBorder(parentWM));
+        LogicalRect rect(wm, LogicalPoint(wm), aMetrics.Size(wm));
+        rect.Deflate(wm, aReflowInput.ComputedLogicalBorder(wm));
         return rect;
       }();
       AbsPosReflowFlags flags{AbsPosReflowFlag::AllowFragmentation};
@@ -1713,8 +1711,8 @@ void nsBlockFrame::Reflow(nsPresContext* aPresContext, ReflowOutput& aMetrics,
       SetupLineCursorForQuery();
       absoluteContainer->Reflow(
           this, aPresContext, aReflowInput, reflowStatus,
-          containingBlock.GetPhysicalRect(parentWM, aMetrics.PhysicalSize()),
-          flags, &aMetrics.mOverflowAreas);
+          containingBlock.GetPhysicalRect(wm, aMetrics.PhysicalSize()), flags,
+          &aMetrics.mOverflowAreas);
     }
   }