Adapt and reland old position sticky implementation

third_party/WebKit/Source/core/css/resolver/StyleAdjuster.cpp

 /*
  * Copyright (C) 1999 Lars Knoll (knoll@kde.org)
  *           (C) 2004-2005 Allan Sandfeld Jensen (kde@carewolf.com)
  * Copyright (C) 2006, 2007 Nicholas Shanks (webkit@nickshanks.com)
  * Copyright (C) 2005, 2006, 2007, 2008, 2009, 2010, 2011, 2012, 2013 Apple Inc. All rights reserved.
  * Copyright (C) 2007 Alexey Proskuryakov <ap@webkit.org>
  * Copyright (C) 2007, 2008 Eric Seidel <eric@webkit.org>
  * Copyright (C) 2008, 2009 Torch Mobile Inc. All rights reserved. (http://www.torchmobile.com/)
  * Copyright (c) 2011, Code Aurora Forum. All rights reserved.
  * Copyright (C) Research In Motion Limited 2011. All rights reserved.
@@ skipping 179 matching lines @@
     // object wedged in between them. Auto z-index also becomes 0 for objects that specify transforms/masks/reflections.
     if (style.hasAutoZIndex() && ((e && e->document().documentElement() == e)
         || style.hasOpacity()
         || style.hasTransformRelatedProperty()
         || style.hasMask()
         || style.clipPath()
         || style.boxReflect()
         || style.hasFilter()
         || style.hasBlendMode()
         || style.hasIsolation()
-        || style.position() == FixedPosition
+        || style.hasViewportConstrainedPosition()
         || isInTopLayer(e, style)
         || hasWillChangeThatCreatesStackingContext(style)))
         style.setZIndex(0);
 
     if (doesNotInheritTextDecoration(style, e))
         style.clearAppliedTextDecorations();
 
     style.applyTextDecorations();
 
     if (style.overflowX() != OVISIBLE || style.overflowY() != OVISIBLE)
@@ skipping 246 matching lines @@
         style.setDisplay(INLINE_BLOCK);
 
     // After performing the display mutation, check table rows. We do not honor position: relative table rows or cells.
     // This has been established for position: relative in CSS2.1 (and caused a crash in containingBlock()
     // on some sites).
     if ((style.display() == TABLE_HEADER_GROUP || style.display() == TABLE_ROW_GROUP
         || style.display() == TABLE_FOOTER_GROUP || style.display() == TABLE_ROW)
         && style.position() == RelativePosition)
         style.setPosition(StaticPosition);
 
+    // Cannot support position: sticky for table columns and column groups because current code is only doing
+    // background painting through columns / column groups

[chrishtr, 2015/10/06 17:08:33]

Is this recorded in a bug?

According to this spec:

https://drafts.csswg.org/css-position-3/#valdef-position-sticky

position: sticky is not supposed to apply to any table elements.

[flackr, 2015/10/07 20:38:12]

Hmm, doesn't look like it, just the bug for a crash allowing sticky in this
context used to cause. See the original review:
https://codereview.chromium.org/196413002/

According to https://bugs.webkit.org/show_bug.cgi?id=112024 table rows should be
able to stick. Perhaps I'm mistaken, but my reading of the spec was that for
table elements it should have the same ability to "offset" as relative does
(https://drafts.csswg.org/css-position-3/#valdef-position-relative) - which I
thought meant that columns and column groups will not be offset but rows and row
groups can be offset. There are even a couple tests for this:
fast/css/sticky/sticky-table-row-top.html
fast/css/sticky/sticky-table-thead-top.html 

It is strange that this doesn't seem to be consistent with the code above which
suggests that header groups, row groups, footer groups and rows do not offset.
It also looks like there are known bugs with table rows being absolute position
containing blocks (http://crbug.com/443190)...

[chrishtr, 2015/11/04 01:40:43]

The spec says: "The effect of position: sticky on table elements is the same as
for position: relative". Doesn't that mean that table elements can't be sticky?

As crbug.com/443190 indicates (I duped it into another bug BTW), tables are
special and some of the subclasses can't be containing
blocks in our current implementation. This may actually be a constraint of the
way they are spec'ed, I never got to the bottom of looking into that.

See https://code.google.com/p/chromium/issues/detail?id=477495#c9

I think we should likely only support sticky for LayoutTable, but not any of the
other table-related classes. Maybe also LayoutTableCell?

It appears the lines in this function implement that restriction? Please confirm
and add a comment explaining.

[flackr, 2015/11/25 21:03:01]

There are many public examples where sticky is used on a table row to produce an
always visible table header. I do believe it is intended to work on table rows.

Under position: relative on
https://drafts.csswg.org/css-position/#valdef-position-relative it says that
only table-column-group and table-column do not offset.

+    if ((style.display() == TABLE_COLUMN_GROUP || style.display() == TABLE_COLUMN)
+        && style.position() == StickyPosition)
+        style.setPosition(StaticPosition);
+
     // writing-mode does not apply to table row groups, table column groups, table rows, and table columns.
     // FIXME: Table cells should be allowed to be perpendicular or flipped with respect to the table, though.
     if (style.display() == TABLE_COLUMN || style.display() == TABLE_COLUMN_GROUP || style.display() == TABLE_FOOTER_GROUP
         || style.display() == TABLE_HEADER_GROUP || style.display() == TABLE_ROW || style.display() == TABLE_ROW_GROUP
         || style.display() == TABLE_CELL)
         style.setWritingMode(parentStyle.writingMode());
 
     // FIXME: Since we don't support block-flow on flexible boxes yet, disallow setting
     // of block-flow to anything other than TopToBottomWritingMode.
     // https://bugs.webkit.org/show_bug.cgi?id=46418 - Flexible box support.
     if (style.writingMode() != TopToBottomWritingMode && (style.display() == BOX || style.display() == INLINE_BOX))
         style.setWritingMode(TopToBottomWritingMode);
 
     if (parentStyle.isDisplayFlexibleOrGridBox()) {
         style.setFloating(NoFloat);
         style.setDisplay(equivalentBlockDisplay(style.display(), style.isFloating(), !m_useQuirksModeStyles));
 
         // We want to count vertical percentage paddings/margins on flex items because our current
         // behavior is different from the spec and we want to gather compatibility data.
         if (style.paddingBefore().hasPercent() || style.paddingAfter().hasPercent())
             UseCounter::count(document, UseCounter::FlexboxPercentagePaddingVertical);
         if (style.marginBefore().hasPercent() || style.marginAfter().hasPercent())
             UseCounter::count(document, UseCounter::FlexboxPercentageMarginVertical);
     }
 }
 
 }