From ae6fa4834c00b10df8cf2ac96b7358c7a45dd3e0 Mon Sep 17 00:00:00 2001
From: Ting-Yu Lin <tlin@mozilla.com>
Date: Tue, 8 Feb 2022 22:47:20 +0000
Subject: [PATCH] Bug 1752658 Part 7 - Generalize GenerateFlexLines to populate
 FlexLayoutResult. r=dholbert

Differential Revision: https://phabricator.services.mozilla.com/D138101
---
 layout/generic/nsFlexContainerFrame.cpp | 27 +++++++++++++++----------
 layout/generic/nsFlexContainerFrame.h   |  9 ++++-----
 2 files changed, 20 insertions(+), 16 deletions(-)

diff --git a/layout/generic/nsFlexContainerFrame.cpp b/layout/generic/nsFlexContainerFrame.cpp
index 1b2c55d4d863..5844ae673a41 100644
--- a/layout/generic/nsFlexContainerFrame.cpp
+++ b/layout/generic/nsFlexContainerFrame.cpp
@@ -4233,12 +4233,17 @@ void nsFlexContainerFrame::GenerateFlexLines(
   }
 }
 
-void nsFlexContainerFrame::GenerateFlexLines(const SharedFlexData& aData,
-                                             nsTArray<FlexLine>& aLines) {
+nsFlexContainerFrame::FlexLayoutResult
+nsFlexContainerFrame::GenerateFlexLayoutResult() {
   MOZ_ASSERT(GetPrevInFlow(), "This should be called by non-first-in-flows!");
 
+  auto* data = FirstInFlow()->GetProperty(SharedFlexData::Prop());
+  MOZ_ASSERT(data, "SharedFlexData should be set by our first-in-flow!");
+
+  FlexLayoutResult flr;
+
   // Pretend we have only one line and zero main gap size.
-  aLines.AppendElement(FlexLine(0));
+  flr.mLines.AppendElement(FlexLine(0));
 
   // The order state of the children is consistent across entire continuation
   // chain due to calling nsContainerFrame::NormalizeChildLists() at the
@@ -4255,7 +4260,7 @@ void nsFlexContainerFrame::GenerateFlexLines(const SharedFlexData& aData,
       CSSOrderAwareFrameIterator::ChildFilter::SkipPlaceholders,
       OrderStateForIter(this), OrderingPropertyForIter(this));
 
-  FlexItemIterator itemIter(aData.mLines);
+  FlexItemIterator itemIter(data->mLines);
 
   for (; !iter.AtEnd(); iter.Next()) {
     nsIFrame* const child = *iter;
@@ -4266,12 +4271,17 @@ void nsFlexContainerFrame::GenerateFlexLines(const SharedFlexData& aData,
 
     for (; !itemIter.AtEnd(); itemIter.Next()) {
       if (itemIter->Frame() == childFirstInFlow) {
-        aLines[0].Items().AppendElement(itemIter->CloneFor(child));
+        flr.mLines[0].Items().AppendElement(itemIter->CloneFor(child));
         itemIter.Next();
         break;
       }
     }
   }
+
+  flr.mContentBoxMainSize = data->mContentBoxMainSize;
+  flr.mContentBoxCrossSize = data->mContentBoxCrossSize;
+
+  return flr;
 }
 
 // Returns the largest outer hypothetical main-size of any line in |aLines|.
@@ -4600,12 +4610,7 @@ void nsFlexContainerFrame::Reflow(nsPresContext* aPresContext,
                          containerInfo);
     }
   } else {
-    auto* data = FirstInFlow()->GetProperty(SharedFlexData::Prop());
-    MOZ_ASSERT(data, "SharedFlexData should be set by our first-in-flow!");
-
-    GenerateFlexLines(*data, flr.mLines);
-    flr.mContentBoxMainSize = data->mContentBoxMainSize;
-    flr.mContentBoxCrossSize = data->mContentBoxCrossSize;
+    flr = GenerateFlexLayoutResult();
   }
 
   const LogicalSize contentBoxSize =
diff --git a/layout/generic/nsFlexContainerFrame.h b/layout/generic/nsFlexContainerFrame.h
index 61802dda029d..3d151d3b11c3 100644
--- a/layout/generic/nsFlexContainerFrame.h
+++ b/layout/generic/nsFlexContainerFrame.h
@@ -456,12 +456,11 @@ class nsFlexContainerFrame final : public nsContainerFrame {
                          nsTArray<FlexLine>& aLines);
 
   /**
-   * This method creates FlexLines and FlexItems for children in flex
-   * container's next-in-flows by using the SharedFlexData stored in flex
-   * container's first-in-flow. Returns FlexLines in the outparam |aLines|.
+   * Generates and returns a FlexLayoutResult that contains the FlexLines and
+   * some sizing metrics that should be used to lay out a particular flex
+   * container continuation (i.e. don't call this on the first-in-flow).
    */
-  void GenerateFlexLines(const SharedFlexData& aData,
-                         nsTArray<FlexLine>& aLines);
+  FlexLayoutResult GenerateFlexLayoutResult();
 
   /**
    * Resolves the content-box main-size of a flex container frame,