Bug 451791 patch 2 - Report block non-empty to its parent block during margin collapsing if we encounter clearance. r=roc
authorL. David Baron <dbaron@dbaron.org>
Wed, 05 Aug 2015 21:04:38 -0700
changeset 288139 9e5e1a1f4f20ea3ca09807b86bd19eb108fa5700
parent 288138 8c47f6709cf5284a46b95154accf1bd801442c9c
child 288140 d00d3d7ffd7d5e8610b893c68be7c12ea73f47df
push id5067
push userraliiev@mozilla.com
push dateMon, 21 Sep 2015 14:04:52 +0000
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Bug 451791 patch 2 - Report block non-empty to its parent block during margin collapsing if we encounter clearance. r=roc The goal of ComputeCollapsedBStartMargin is to collapse all of the margins that collapse with a block's top margin. It does this by scanning forward through the child list until it finds something that blocks collapsing; it descends into children through recursion. When we find a non-empty block or line, we stop collapsing and report to the parent that the child is non-empty so that it stops collapsing as well. This patch changes our behavior when we have clearance to do the same thing that we do for non-empty lines or blocks (which makes both occurrences of |goto done| be preceded by the same code). Without the patch we would fail to report being non-empty to the parent (and instead report emptiness based on the IsEmpty() method). This meant that, without the patch, if a block has a child with clearance but also has IsEmpty() true, we would stop scanning margins in that block after the clearance, but start searching again for margins in the block's parent, starting with the block's bottom margin. This patch sets *aBlockIsEmpty to true in that case so that we do not pick up again in the block's parent (or, potentially, grandparent, etc.).
--- a/layout/generic/nsBlockReflowContext.cpp
+++ b/layout/generic/nsBlockReflowContext.cpp
@@ -131,16 +131,20 @@ nsBlockReflowContext::ComputeCollapsedBS
         if (line->IsInline()) {
           isEmpty = line->IsEmpty();
         } else {
           nsIFrame* kid = line->mFirstChild;
           if (kid == aClearanceFrame) {
             dirtiedLine = true;
+            if (!setBlockIsEmpty && aBlockIsEmpty) {
+              setBlockIsEmpty = true;
+              *aBlockIsEmpty = false;
+            }
             goto done;
           // Here is where we recur. Now that we have determined that a
           // generational collapse is required we need to compute the
           // child blocks margin and so in so that we can look into
           // it. For its margins to be computed we need to have a reflow
           // state for it.
--- a/layout/reftests/margin-collapsing/reftest.list
+++ b/layout/reftests/margin-collapsing/reftest.list
@@ -761,18 +761,18 @@ fails-if(Android&&AndroidVersion==18) !=
 == block-float-1a-dyn.html block-float-1a-ref.html
 == block-float-1b-dyn.html block-float-1b-ref.html
 == block-float-2a-dyn.html block-float-2a-ref.html
 == block-float-2b-dyn.html block-float-2b-ref.html
 == block-float-3a-dyn.html block-float-3a-ref.html
 == block-float-3b-dyn.html block-float-3b-ref.html
 # Tests for various cases where clearance is applied and collapsing is
 # prevented or only allows for certain margins.
-fails == block-clear-1a.html block-clear-1a-ref.html # Bug 451791
-fails == block-clear-1b.html block-clear-1b-ref.html # Bug 451791
+== block-clear-1a.html block-clear-1a-ref.html
+== block-clear-1b.html block-clear-1b-ref.html
 == block-clear-2.html block-clear-2-ref.html
 != block-clear-2.html block-clear-2-noref.html
 == block-clear-3a.html block-clear-3-ref-left.html
 == block-clear-3b.html block-clear-3-ref-right.html
 == block-clear-3c.html block-clear-3-ref-left.html
 == block-clear-3d.html block-clear-3-ref-right.html
 == block-clear-3e.html block-clear-3-ref-left.html
 == block-clear-3f.html block-clear-3-ref-right.html