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Commit 86d53e7b authored by mstensho's avatar mstensho Committed by Commit bot
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Adjust column rows' height better for their offset in the multicol container. 

We were missing the case where the first object in a multicol container was a
spanner (the call to previousSiblingMultiColumnSet() should have been
previousSiblingMultiColumnBox(), to catch spanner placeholders in addition to
column sets).

But instead of having a special code path depending on whether we're dealing
with the first box or not (to avoid subtracting the multicol container's top
border and padding from an uncalculated logical top of a column set), always
subtract the margin top edge of the first column box instead.

R=leviw@chromium.org

Review URL: https://codereview.chromium.org/1631633002

Cr-Commit-Position: refs/heads/master@{#371661}
parent 787c2d79
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Showing with 47 additions and 15 deletions
third_party/WebKit/LayoutTests/fast/multicol/span/autofill-after-spanner.html 0 → 100644
View file @ 86d53e7b
<!DOCTYPE html>
<script src="../../../resources/check-layout.js"></script>
<p>There should be a blue square below.</p>
<div id="multicol" style="position:relative; padding:25px; -webkit-columns:2; -webkit-column-gap:0; column-fill:auto; line-height:20px; width:60px; height:100px;">
<div style="-webkit-column-span:all; margin-top:20px; height:20px;"></div>
<div style="background:blue;">
<div data-offset-x="25" data-offset-y="65"><br></div>
<div data-offset-x="25" data-offset-y="85"><br></div>
<div data-offset-x="25" data-offset-y="105"><br></div>
<div data-offset-x="55" data-offset-y="65"><br></div>
<div data-offset-x="55" data-offset-y="85"><br></div>
<div data-offset-x="55" data-offset-y="105"><br></div>
</div>
</div>
<script>
checkLayout("#multicol");
</script>
third_party/WebKit/Source/core/layout/LayoutMultiColumnSet.cpp
View file @ 86d53e7b
......@@ -170,6 +170,22 @@ MultiColumnFragmentainerGroup& LayoutMultiColumnSet::appendNewFragmentainerGroup
return m_fragmentainerGroups.last();
}
LayoutUnit LayoutMultiColumnSet::logicalTopFromMulticolContentEdge() const
{
// We subtract the position of the first column set or spanner placeholder, rather than the
// "before" border+padding of the multicol container. This distinction doesn't matter after
// layout, but during layout it does: The flow thread (i.e. the multicol contents) is laid out
// before the column sets and spanner placeholders, which means that compesating for a top
// border+padding that hasn't yet been baked into the offset will produce the wrong results in
// the first layout pass, and we'd end up performing a wasted layout pass in many cases.
const LayoutBox& firstColumnBox = *multiColumnFlowThread()->firstMultiColumnBox();
// The top margin edge of the first column set or spanner placeholder is flush with the top
// content edge of the multicol container. The margin here never collapses with other margins,
// so we can just subtract it. Column sets never have margins, but spanner placeholders may.
LayoutUnit firstColumnBoxMarginEdge = firstColumnBox.logicalTop() - multiColumnBlockFlow()->marginBeforeForChild(firstColumnBox);
return logicalTop() - firstColumnBoxMarginEdge;
}
LayoutUnit LayoutMultiColumnSet::logicalTopInFlowThread() const
{
return firstFragmentainerGroup().logicalTopInFlowThread();
......
third_party/WebKit/Source/core/layout/LayoutMultiColumnSet.h
View file @ 86d53e7b
......@@ -101,6 +101,9 @@ public:
MultiColumnFragmentainerGroup& appendNewFragmentainerGroup();
// Logical top relative to the content edge of the multicol container.
LayoutUnit logicalTopFromMulticolContentEdge() const;
LayoutUnit logicalTopInFlowThread() const;
LayoutUnit logicalBottomInFlowThread() const;
LayoutUnit logicalHeightInFlowThread() const { return logicalBottomInFlowThread() - logicalTopInFlowThread(); }
......
third_party/WebKit/Source/core/layout/MultiColumnFragmentainerGroup.cpp
View file @ 86d53e7b
......@@ -292,21 +292,8 @@ unsigned MultiColumnFragmentainerGroup::actualColumnCount() const
LayoutUnit MultiColumnFragmentainerGroup::heightAdjustedForRowOffset(LayoutUnit height) const
{
// Adjust for the top offset within the content box of the multicol container (containing
// block), unless we're in the first set. We know that the top offset for the first set will be
// zero, but if the multicol container has non-zero top border or padding, the set's top offset
// (initially being 0 and relative to the border box) will be negative until it has been laid
// out. Had we used this bogus offset, we would calculate the wrong height, and risk performing
// a wasted layout iteration. Of course all other sets (if any) have this problem in the first
// layout pass too, but there's really nothing we can do there until the flow thread has been
// laid out anyway.
if (m_columnSet.previousSiblingMultiColumnSet()) {
LayoutBlockFlow* multicolBlock = m_columnSet.multiColumnBlockFlow();
LayoutUnit contentLogicalTop = m_columnSet.logicalTop() - multicolBlock->borderAndPaddingBefore();
height -= contentLogicalTop;
}
height -= logicalTop();
return max(height, LayoutUnit(1)); // Let's avoid zero height, as that would probably cause an infinite amount of columns to be created.
// Let's avoid zero height, as that would cause an infinite amount of columns to be created.
return std::max(height - logicalTop() - m_columnSet.logicalTopFromMulticolContentEdge(), LayoutUnit(1));
}
LayoutUnit MultiColumnFragmentainerGroup::calculateMaxColumnHeight() const
......
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