[LFC][Integration] Allow subpixel difference in the computed containing block height when switching between line layout systems

alanbaradlay · alanbaradlay · commit 2a1d81a2a394 · 2020-11-19T14:18:29.000Z
https://bugs.webkit.org/show_bug.cgi?id=219143 Reviewed by Antti Koivisto. With all the seemingly random flooring, ceiling and rounding in the legacy line layout codebase, it's really difficult to subpixel match the end result in a sane way in IFC as we start supporting more complex content. * rendering/RenderBlockFlow.cpp: (WebCore::RenderBlockFlow::ensureLineBoxes): Canonical link: https://commits.webkit.org/231767@main git-svn-id: https://svn.webkit.org/repository/webkit/trunk@270026 268f45cc-cd09-0410-ab3c-d52691b4dbfc
diff --git a/Source/WebCore/ChangeLog b/Source/WebCore/ChangeLog
@@ -1,3 +1,16 @@
+2020-11-19  Zalan Bujtas  <zalan@apple.com>
+
+        [LFC][Integration] Allow subpixel difference in the computed containing block height when switching between line layout systems
+        https://bugs.webkit.org/show_bug.cgi?id=219143
+
+        Reviewed by Antti Koivisto.
+
+        With all the seemingly random flooring, ceiling and rounding in the legacy line layout codebase,
+        it's really difficult to subpixel match the end result in a sane way in IFC as we start supporting more complex content.
+
+        * rendering/RenderBlockFlow.cpp:
+        (WebCore::RenderBlockFlow::ensureLineBoxes):
+
 2020-11-19  Antti Koivisto  <antti@apple.com>
 
         [LFC][Integration] nextLinePosition should use iterator
diff --git a/Source/WebCore/rendering/RenderBlockFlow.cpp b/Source/WebCore/rendering/RenderBlockFlow.cpp
@@ -3687,7 +3687,7 @@ void RenderBlockFlow::ensureLineBoxes()
         complexLineLayout.layoutLineBoxes(relayoutChildren, repaintLogicalTop, repaintLogicalBottom);
 
     updateLogicalHeight();
-    ASSERT(didNeedLayout || logicalHeight() == oldHeight);
+    ASSERT(didNeedLayout || ceilf(logicalHeight()) == ceilf(oldHeight));
 
     if (!didNeedLayout)
         clearNeedsLayout();
