Changeset 176285 in webkit

Timestamp:

Nov 18, 2014, 2:40:29 PM (12 years ago)

Author:

mmaxfield@apple.com

Message:

Multicolumn layout with negative line spacing and orphans causes pieces of letters to be shown at the bottom of columns
​https://bugs.webkit.org/show_bug.cgi?id=138204

Source/WebCore:

Reviewed by Dave Hyatt.

This code is responsible for pushing block elements to the next column if
the "orphans" CSS property is triggered. The mechanism by which this is
achieved is to push the block down such that the origin of the block is
at the origin of the next column. However, if there is negative line
spacing, the top portion of the text might actually be on top of the
origin of the block. Therefore, the block wasn't being pushed down enough
to entirely contain its text, so the top pieces were being drawn on the
previous column.

Test: fast/multicol/orphans-negative-line-spacing.html

• rendering/RenderBlockFlow.cpp:

(WebCore::RenderBlockFlow::adjustLinePositionForPagination):

LayoutTests:

Patch by Myles C. Maxfield <​litherum@gmail.com> on 2014-11-18
Reviewed by Dave Hyatt.

Create a layout where the "orphans" css property causes a block element to
be pushed to the next column.

• fast/multicol/orphans-negative-line-spacing-expected.html: Added.
• fast/multicol/orphans-negative-line-spacing.html: Added.

Location:

trunk

Files:

• LayoutTests/ChangeLog (modified) (1 diff)
• LayoutTests/fast/multicol/orphans-negative-line-spacing-expected.html (added)
• LayoutTests/fast/multicol/orphans-negative-line-spacing.html (added)
• Source/WebCore/ChangeLog (modified) (1 diff)
• Source/WebCore/rendering/RenderBlockFlow.cpp (modified) (1 diff)

trunk/LayoutTests/ChangeLog

@@ +1 @@
+2014-11-18  Myles C. Maxfield  <litherum@gmail.com>
+
+        Multicolumn layout with negative line spacing and orphans causes pieces of letters to be shown at the bottom of columns
+        https://bugs.webkit.org/show_bug.cgi?id=138204
+
+        Reviewed by Dave Hyatt.
+
+        Create a layout where the "orphans" css property causes a block element to
+        be pushed to the next column.
+
+        * fast/multicol/orphans-negative-line-spacing-expected.html: Added.
+        * fast/multicol/orphans-negative-line-spacing.html: Added.
+
 2014-11-18  Chris Dumez  <cdumez@apple.com>
 

trunk/Source/WebCore/ChangeLog

@@ +1 @@
+2014-11-18  Myles C. Maxfield  <mmaxfield@apple.com>
+
+        Multicolumn layout with negative line spacing and orphans causes pieces of letters to be shown at the bottom of columns
+        https://bugs.webkit.org/show_bug.cgi?id=138204
+
+        Reviewed by Dave Hyatt.
+
+        This code is responsible for pushing block elements to the next column if
+        the "orphans" CSS property is triggered. The mechanism by which this is
+        achieved is to push the block down such that the origin of the block is
+        at the origin of the next column. However, if there is negative line
+        spacing, the top portion of the text might actually be on top of the
+        origin of the block. Therefore, the block wasn't being pushed down enough
+        to entirely contain its text, so the top pieces were being drawn on the
+        previous column.
+
+        Test: fast/multicol/orphans-negative-line-spacing.html
+
+        * rendering/RenderBlockFlow.cpp:
+        (WebCore::RenderBlockFlow::adjustLinePositionForPagination):
+
 2014-11-18  Chris Dumez  <cdumez@apple.com>
 

trunk/Source/WebCore/rendering/RenderBlockFlow.cpp

@@ -1668 +1668 @@
         setPageBreak(logicalOffset, lineHeight - remainingLogicalHeight);
         if (((lineBox == firstRootBox() && totalLogicalHeight < pageLogicalHeightAtNewOffset) || (!style().hasAutoOrphans() && style().orphans() >= lineIndex))
-            && !isOutOfFlowPositioned() && !isTableCell())
-            setPaginationStrut(remainingLogicalHeight + std::max<LayoutUnit>(0, logicalOffset));
-        else {
+            && !isOutOfFlowPositioned() && !isTableCell()) {
+            auto firstRootBox = this->firstRootBox();
+            auto firstRootBoxOverflowRect = firstRootBox->logicalVisualOverflowRect(firstRootBox->lineTop(), firstRootBox->lineBottom());
+            auto firstLineUpperOverhang = std::max(-firstRootBoxOverflowRect.y(), LayoutUnit());
+            setPaginationStrut(remainingLogicalHeight + logicalOffset + firstLineUpperOverhang);
+        } else {
             delta += remainingLogicalHeight;
             lineBox->setPaginationStrut(remainingLogicalHeight);