Bug 1679819 Part 2 - Compute abs-pos elements' available block-size, …

…and pass it to ReflowInput's constructor. r=layout-reviewers,emilio This ensures abs-pos frame with size containment is monolithic because ReflowInput::Init() can override available block-size to an unconstrained size if the frame has size containment (Bug 1470329). Differential Revision: https://phabricator.services.mozilla.com/D98227
dothq · Dec 1, 2020 · c72f25a · c72f25a
1 parent 28ddd5d
commit c72f25a
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Showing 2 changed files with 46 additions and 7 deletions.
diff --git a/layout/generic/nsAbsoluteContainingBlock.cpp b/layout/generic/nsAbsoluteContainingBlock.cpp
@@ -712,9 +712,6 @@ void nsAbsoluteContainingBlock::ReflowAbsoluteFrame(
       initFlags += ReflowInput::InitFlag::StaticPosIsCBOrigin;
     }
   }
-  ReflowInput kidReflowInput(aPresContext, aReflowInput, aKidFrame,
-                             LogicalSize(wm, availISize, NS_UNCONSTRAINEDSIZE),
-                             Some(logicalCBSize), initFlags);
 
   bool constrainBSize =
       (aReflowInput.AvailableBSize() != NS_UNCONSTRAINEDSIZE) &&
@@ -739,10 +736,18 @@ void nsAbsoluteContainingBlock::ReflowAbsoluteFrame(
   const WritingMode outerWM = aReflowInput.GetWritingMode();
   const LogicalMargin border = aDelegatingFrame->GetLogicalUsedBorder(outerWM);
 
-  if (constrainBSize) {
-    kidReflowInput.AvailableBSize() =
-        aReflowInput.AvailableBSize() -
-        border.ConvertTo(wm, outerWM).BStart(wm) -
+  const nscoord availBSize = constrainBSize
+                                 ? aReflowInput.AvailableBSize() -
+                                       border.ConvertTo(wm, outerWM).BStart(wm)
+                                 : NS_UNCONSTRAINEDSIZE;
+
+  ReflowInput kidReflowInput(aPresContext, aReflowInput, aKidFrame,
+                             LogicalSize(wm, availISize, availBSize),
+                             Some(logicalCBSize), initFlags);
+
+  if (kidReflowInput.AvailableBSize() != NS_UNCONSTRAINEDSIZE) {
+    // Shrink available block-size if it's constrained.
+    kidReflowInput.AvailableBSize() -=
         kidReflowInput.ComputedLogicalMargin(wm).BStart(wm);
     const nscoord kidOffsetBStart =
         kidReflowInput.ComputedLogicalOffsets(wm).BStart(wm);

diff --git a/testing/web-platform/tests/css/css-contain/contain-size-monolithic-002.html b/testing/web-platform/tests/css/css-contain/contain-size-monolithic-002.html
@@ -0,0 +1,34 @@
+<!DOCTYPE html>
+<html>
+  <meta charset="UTF-8">
+  <title>CSS Containment Test: absolute positioned 'contain: size' element is monolithic</title>
+  <link rel="author" title="Ting-Yu Lin" href="mailto:[email protected]">
+  <link rel="author" title="Mozilla" href="https://www.mozilla.org/">
+  <link rel="help" href="https://drafts.csswg.org/css-contain-1/#containment-size">
+  <link rel="match" href="../reference/ref-filled-green-100px-square-only.html">
+  <meta  name="assert" content="This test checks that an absolute positioned element with size containment is monolithic.">
+
+  <style>
+  #multicol {
+    width: 300px;
+    column-count: 3;
+  }
+  #container {
+    position: relative;
+  }
+  #abs-size-contain {
+    position: absolute;
+    contain: size;
+    width: 100px;
+    height: 100px;
+    background: green;
+  }
+  </style>
+
+  <p>Test passes if there is a filled green square.</p>
+  <div id="multicol">
+    <div id="container">
+      <div id="abs-size-contain"></div>
+    </div>
+  </div>
+</html>